Re: nested subroutines
Chris Stinemetz wrote: Thanks in advance. I have a subroutine inside another subroutine in a module I am tyring to put together. I would like to pass the value assigned to $srt in the while loop as the parameter for the session_attempts subroutine called withing the processPegs subroutine. The error I am getting is: Use of uninitialized value $_srt in numeric ne (!=) at ... The code provided does not use the ne operator nor does it use the variable $_srt John -- Any intelligent fool can make things bigger and more complex... It takes a touch of genius - and a lot of courage to move in the opposite direction. -- Albert Einstein -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: nested subroutines
Sent from my iPhone On Mar 2, 2013, at 7:49 PM, John W. Krahn jwkr...@shaw.ca wrote: Chris Stinemetz wrote: Thanks in advance. I have a subroutine inside another subroutine in a module I am tyring to put together. I would like to pass the value assigned to $srt in the while loop as the parameter for the session_attempts subroutine called withing the processPegs subroutine. The error I am getting is: Use of uninitialized value $_srt in numeric ne (!=) at ... The code provided does not use the ne operator nor does it use the variable $_srt John -- Any intelligent fool can make things bigger and more complex... It takes a touch of genius - and a lot of courage to move in the opposite direction. -- Albert Einstein -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/ Correct. I was able to figure it out. Thanks, Chris -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: nested loops
MMH == Mark M Huntress mar...@bgsu.edu writes:
MMH I want to nest a for loop in a for loop in a while loop, and I
MMH can't even get just the first nesting to work yet. Here is the
MMH relevant part of my scripting.
MMH open(XYZ,$ARGV[0]ready.xyz);
don't use @ARGV stuff like that before you check that you have args.
always check for success with open calls
also use lexical handles for i/o.
all of these are common points you can google for more info
MMH #while (XYZ) {
MMH #chomp($_);
MMH for ($z = 0, $z = $#sortedstart, $z++) {
where did you get that syntax from? it isn't any normal perl loop. in
fact it is a foreach loop over 3 values (afaict) and nothing close to
what you envisioned it to be.
read perldoc perlsyn for the two ways to write for loops - a c style and
a perl foreach style. yours is a strange conjunction of the two styles
and makes no sense at all.
uri
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Re: nested loops
On 10-12-20 07:04 PM, Mark M Huntress wrote:
open(XYZ,$ARGV[0]ready.xyz);
The three argument open is preferred and always check your opens for errors.
my $file = $ARGV[0]ready.xyz;
open my $xyz_fh, '', $file or die could not open $file: $!\n;
#while (XYZ) {
#chomp($_);
while( $xyz_fh ){
chomp;
for ($z = 0, $z= $#sortedstart, $z++) {
for ($i = $sortedstart[$z], $i= $sortedend[$z], $i++) {
It's hard to determine what these for statements are doing without
knowing what's in the arrays.
if ($_ =~ /^\s+$i\s+(\D).*\s+(.+\.\d+\s+.+\.\d+\s+.+\.\d+)\s+/) {
For complex patterns, use the /x to allow whitespace in them. See
`perldoc perlre` and read the section on Modifiers
$count++;
print CON $count $count $10 $2\n;
}
print \nz is $z\n;
print \ni is $i\n;
}
}
I am expecting it to cycle through several $i values and also $z values. When
it prints the values, it only gives $z=1.
Does anyone see why this isn't working?
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Re: nested loops
On 21/12/2010 00:04, Mark M Huntress wrote:
I want to nest a for loop in a for loop in a while loop, and I can't
even get just the first nesting to work yet. Here is the relevant
part of my scripting.
open(XYZ,$ARGV[0]ready.xyz);
#while (XYZ) {
#chomp($_);
for ($z = 0, $z= $#sortedstart, $z++) {
for ($i = $sortedstart[$z], $i= $sortedend[$z], $i++) {
if ($_ =~ /^\s+$i\s+(\D).*\s+(.+\.\d+\s+.+\.\d+\s+.+\.\d+)\s+/) {
$count++;
print CON $count $count $10 $2\n;
}
print \nz is $z\n;
print \ni is $i\n;
}
}
I am expecting it to cycle through several $i values and also $z
values. When it prints the values, it only gives $z=1.
Does anyone see why this isn't working?
Hi Mark
You have written the for statements
for ($z = 0, $z= $#sortedstart, $z++) {
for ($i = $sortedstart[$z], $i= $sortedend[$z], $i++) {
with commas instead of semicolons. Also, this is the C form of the for
loop, and almost never the right thing to do in Perl. Instead use
for my $z (0 ... $#sortedstart) {
for my $i ($sortedstart[$z] ... $sortedend[$z]) {
The advice you have been given in the other replies is good, and you
should take note of that as well.
HTH,
Rob
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Re: nested loops
Mark M Huntress wrote:
I want to nest a for loop in a for loop in a while loop, and I can't
even get just the first nesting to work yet. Here is the relevant part
of my scripting.
open(XYZ,$ARGV[0]ready.xyz);
Better as:
open XYZ, '', $ARGV[0]ready.xyz
or die Cannot open '$ARGV[0]ready.xyz' because: $!;
#while (XYZ) {
#chomp($_);
for ($z = 0, $z= $#sortedstart, $z++) {
You are iterating over a list of three numbers. If @sortedstart is
empty then you get:
for $_ ( 0, 0, 0 ) {
If @sortedstart is NOT empty then you get:
for $_ ( 0, 1, 0 ) {
What you probably want is:
for my $z ( 0 .. $#sortedstart ) {
for ($i = $sortedstart[$z], $i= $sortedend[$z], $i++) {
Again, you are iterating over a list of three numbers. If
$sortedend[$z] is less than $i you get:
for $_ ( $sortedstart[$z], 0, $sortedstart[$z] ) {
If $sortedend[$z] is NOT less than $i you get:
for $_ ( $sortedstart[$z], 1, $sortedstart[$z] ) {
What you probably want is:
for my $i ( $sortedstart[ $z ] .. $sortedend[ $z ] ) {
John
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more complex... It takes a touch of genius -
and a lot of courage to move in the opposite
direction. -- Albert Einstein
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Re: Nested if and elsif and else
Uri Guttman u...@stemsystems.com writes: i disagree that it is elegant. too often if/else lists are not needed. many can be replaced by dispatch tables. if one of the clauses does just a return or next/last that can be replaced with a modifier or shorter statement. without ANY serious work, i have over 10k lines of perl code in one system with about 10 else's and maybe 3 elsif's. it just is a matter of knowing how to manage flow control well and you rarely need else's. Can someone show an example of an if/elsif/else nested construct being replaced by a dispatch table? -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: Nested if and elsif and else
Harry Putnam wrote:
Uri Guttman u...@stemsystems.com writes:
i disagree that it is elegant. too often if/else lists
are not
needed. many can be replaced by dispatch tables. if one
of the clauses
does just a return or next/last that can be replaced
with a modifier or
shorter statement. without ANY serious work, i have over
10k lines of
perl code in one system with about 10 else's and maybe 3
elsif's. it
just is a matter of knowing how to manage flow control
well and you
rarely need else's.
Can someone show an example of an if/elsif/else nested
construct being
replaced by a dispatch table?
--
Here's an example I gave in a similar question in another
forum.
my %dispatch = (
1 = \getcpuinfo,
2 = \osversion,
3 = \loadaverages,
4 = \systemload_uptime,
5 = \netinterfaceinfo,
6 = \diskusage,
7 = \ipaddress,
q = sub { print Goodbye\n and exit; },
error = sub { print invalid selection\n },
);
while(1)
{
print press 1 to get CPU Info \n,
press 2 to get OS version \n,
press 3 to get CPU Load averages\n,
press 4 to get System Load Uptime\n,
press 5 to get Net Interface info\n,
press 6 to get system disk usage info \n,
press 7 to get IP address info \n;
press q to Exit\n
chomp(my $selection) = STDIN;
my $code = $dispatch{$selection} || $dispatch{'error'} ;
$code-();
}
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Re: Nested if and elsif and else
r...@i.frys.com writes: Here's an example I gave in a similar question in another forum. Thanks... I'm sorry to ask more but if someone asked to be shown an if/elsif/else construct being replaced by a dispatch table, I don't really see how that answered there question. It didn't for me. Where is the comparable if/elsif/else construct that is being replaced by the dispatch table? Visualizing how it would go is a little beyond my grasp I guess. -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: Nested if and elsif and else
On 4/15/10 Thu Apr 15, 2010 9:21 AM, Harry Putnam rea...@newsguy.com
scribbled:
r...@i.frys.com writes:
Here's an example I gave in a similar question in another
forum.
Thanks...
I'm sorry to ask more but if someone asked to be shown an
if/elsif/else construct being replaced by a dispatch table, I don't
really see how that answered there question. It didn't for me.
Where is the comparable if/elsif/else construct that is being replaced
by the dispatch table?
Visualizing how it would go is a little beyond my grasp I guess.
Something like this:
print press 1 to get CPU Info \n,
press 2 to get OS version \n,
press 3 to get CPU Load averages\n,
press 4 to get System Load Uptime\n,
press 5 to get Net Interface info\n,
press 6 to get system disk usage info \n,
press 7 to get IP address info \n;
press q to Exit\n
chomp(my $selection) = STDIN;
if( $selection eq '1' ) {
getcpuinfo();
}elsif( $selection eq '2' ) {
osversion();
}elsif{ $selection eq '3' ) {
loadaverages();
}elseif( $selection eq '4' ) {
systemload_uptime();
]elsif(
...
}else{
print Dispatch error\n;
);
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Re: Nested if and elsif and else
On Apr 15, 9:21 am, rea...@newsguy.com (Harry Putnam) wrote: r...@i.frys.com writes: Here's an example I gave in a similar question in another forum. Thanks... I'm sorry to ask more but if someone asked to be shown an if/elsif/else construct being replaced by a dispatch table, I don't really see how that answered there question. It didn't for me. Where is the comparable if/elsif/else construct that is being replaced by the dispatch table? Visualizing how it would go is a little beyond my grasp I guess. Sorry for not posting the if/elsif/else block, but to me that part appeared to be obvious, but I guess it wasn't. I see that Jim has posted the if/elsif/else part, so I won't duplicate it. -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: Nested if and elsif and else
Ron Bergin r...@i.frys.com writes: Sorry for not posting the if/elsif/else block, but to me that part appeared to be obvious, but I guess it wasn't. Probably would have been for all but the densist I guess. Not the first time I've been guilty of that. I see that Jim has posted the if/elsif/else part, so I won't duplicate it. Yes, and thanks to both of you for making it clear even to me. You fella's have lots of patience. -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: Nested if and elsif and else
On Wednesday 14 Apr 2010 02:35:50 Mimi Cafe wrote:
I think this will work, but is it elegant.?
If (condition){
if (nexted_condition){
do this.
}
Elsif (nexted_condition){
Do that...
}
else{
Do something else.
}
}
else{
Do something else..
}
As other people noted, it will work - you can nest if/elsif/else's (and other
flow-control constructs) arbitrarily. However, as Martin Fowler notes in his
book Refactoring ( http://www.refactoring.com/ ) long functions or methods
are a code smell which indicates that one should extract one-or-more functions
out of them. So if you have an inner conditional, consider extracting it into
a function. Often after you have such a function, you can use
return COND() ? TRUE_VAL() : FALSE_VAL() ; which can avoid further
clutter. Or you can consider using a dispatch table like Uri suggested.
I admit I often write quick-and-dirty code that has some levels of nested
constructs (primarily in mostly standalone scripts or programs) but it's
better to refactor them into smaller subroutines for more serious stuff.
Regards,
Shlomi Fish
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Why I Love Perl - http://shlom.in/joy-of-perl
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RE: Nested if and elsif and else
Yes, the nested if and elsif and else makes the code difficult to read and I
often get stuck trying to make sense of it all. For now, I will look to see
if I can move some bit and pieces to subroutines to improve readability.
Thanks guys
Mimi
-Original Message-
From: Jim Gibson [mailto:jimsgib...@gmail.com]
Sent: 14 April 2010 01:36
To: beginners@perl.org
Subject: Re: Nested if and elsif and else
On 4/13/10 Tue Apr 13, 2010 4:35 PM, Mimi Cafe mimic...@googlemail.com
scribbled:
I think this will work, but is it elegant.?
Yes, it will work, and yes, it is elegant, as long as it encapsulates the
logic that is required by your program.
Be sure and watch your indenting, so you can mentally group the correct
branches together (you are a little off in your first 'else'). Also be sure
and put some comments for each conditional that explains what is happening
if it is not obvious (but don't just repeat what is in the condition).
Make sure the 'do this', 'do that', and 'do something else' are not too
long. If they are more than a few statements, use subroutines (with good
names).
If (condition){
if (nexted_condition){
do this.
}
Elsif (nexted_condition){
Do that...
}
else{
Do something else.
}
}
else{
Do something else..
}
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Re: Nested if and elsif and else
On 2010.04.13 23:17, Kenneth Wolcott wrote:
Hi;
On Tue, Apr 13, 2010 at 19:54, Uri Guttman u...@stemsystems.com wrote:
JG == Jim Gibson jimsgib...@gmail.com writes:
JG On 4/13/10 Tue Apr 13, 2010 4:35 PM, Mimi Cafe
mimic...@googlemail.com
JG scribbled:
I think this will work, but is it elegant.?
JG Yes, it will work, and yes, it is elegant, as long as it encapsulates
the
JG logic that is required by your program.
i disagree that it is elegant. too often if/else lists are not
needed. many can be replaced by dispatch tables. if one of the clauses
does just a return or next/last that can be replaced with a modifier or
shorter statement. without ANY serious work, i have over 10k lines of
perl code in one system with about 10 else's and maybe 3 elsif's. it
just is a matter of knowing how to manage flow control well and you
rarely need else's.
uri
I really like the switch statement (native in Perl v5.10) over
anything more complicated than one if/else clause.
I agree with Uri. Even switch statements can be cumbersome depending on
how many cases you have. I believe that (in the majority of cases)
dispatch tables are far more effective, easy to read (like a table of
contents) and maintainable (ie. very easy to add to without having to
worry about placement).
#!/usr/bin/perl
use warnings;
use strict;
my $dt = {
simple = sub { print Simple, anon sub inline\n },
easy= sub { my $num = 1; print $num*2 .\n;},
complex = \complex, # coderef to external sub,
};
sub complex {
my $num = shift;
# ... do a bunch of stuff
print $num\n;
}
# call them
$dt-{ simple }();
$dt-{ easy }();
$dt-{ complex }( 5 );
Steve
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Re: Nested if and elsif and else
Hi Mimi,
Mimi Cafe wrote:
I think this will work, but is it elegant.?
If (condition){
if (nexted_condition){
As others have noted, it will work. But as for elegance, this is a very subjective opinion and
contrary to what recent comments have said, my take on it is that it depends on who intends to look
at this code and what their background is. Is it just you? Or publicly available open source for
potentially everyone? Or just the members of your software engineering team? Are they people with
good Perl backgrounds or are their backgrounds varied and maybe might prefer if...else and switch,
constructs that are available in other languages.
I personally prefer switch and if..else (in that order) since they are based on keywords which my
syntax highlighter picks up easily and are even shown when I print the code out. Also, I can grep
for, if I need to.
Regardless of what you choose, you should also use comments before the block of code to explain what
it is you're doing...
Ray
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Re: Nested if and elsif and else
On 4/13/10 Tue Apr 13, 2010 4:35 PM, Mimi Cafe mimic...@googlemail.com
scribbled:
I think this will work, but is it elegant.?
Yes, it will work, and yes, it is elegant, as long as it encapsulates the
logic that is required by your program.
Be sure and watch your indenting, so you can mentally group the correct
branches together (you are a little off in your first 'else'). Also be sure
and put some comments for each conditional that explains what is happening
if it is not obvious (but don't just repeat what is in the condition).
Make sure the 'do this', 'do that', and 'do something else' are not too
long. If they are more than a few statements, use subroutines (with good
names).
If (condition){
if (nexted_condition){
do this.
}
Elsif (nexted_condition){
Do that...
}
else{
Do something else.
}
}
else{
Do something else..
}
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Re: Nested if and elsif and else
JG == Jim Gibson jimsgib...@gmail.com writes: JG On 4/13/10 Tue Apr 13, 2010 4:35 PM, Mimi Cafe mimic...@googlemail.com JG scribbled: I think this will work, but is it elegant.? JG Yes, it will work, and yes, it is elegant, as long as it encapsulates the JG logic that is required by your program. i disagree that it is elegant. too often if/else lists are not needed. many can be replaced by dispatch tables. if one of the clauses does just a return or next/last that can be replaced with a modifier or shorter statement. without ANY serious work, i have over 10k lines of perl code in one system with about 10 else's and maybe 3 elsif's. it just is a matter of knowing how to manage flow control well and you rarely need else's. uri -- Uri Guttman -- u...@stemsystems.com http://www.sysarch.com -- - Perl Code Review , Architecture, Development, Training, Support -- - Gourmet Hot Cocoa Mix http://bestfriendscocoa.com - -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: Nested if and elsif and else
Hi; On Tue, Apr 13, 2010 at 19:54, Uri Guttman u...@stemsystems.com wrote: JG == Jim Gibson jimsgib...@gmail.com writes: JG On 4/13/10 Tue Apr 13, 2010 4:35 PM, Mimi Cafe mimic...@googlemail.com JG scribbled: I think this will work, but is it elegant.? JG Yes, it will work, and yes, it is elegant, as long as it encapsulates the JG logic that is required by your program. i disagree that it is elegant. too often if/else lists are not needed. many can be replaced by dispatch tables. if one of the clauses does just a return or next/last that can be replaced with a modifier or shorter statement. without ANY serious work, i have over 10k lines of perl code in one system with about 10 else's and maybe 3 elsif's. it just is a matter of knowing how to manage flow control well and you rarely need else's. uri I really like the switch statement (native in Perl v5.10) over anything more complicated than one if/else clause. Ken Wolcott -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: nested loop
Adams Paul wrote:
Hello everyone,
I have a program which navigates to a page and then extracts the links and
navigates
to each of those links.It works fine for the first web page(the program
navigates to
the first page and then extracts the links and visits all the links).When I
then try to get
the program to navigate to the second page (from @page)it puts a http:/// in
the address bar and does
not return a web page. Below is the code:
use LWP::UserAgent; use HTML::LinkExtor; use URI::URL;use
WIN32::IEAutomation;my $ie = Win32::IEAutomation-new( visible = 1, maximize
=
1);@page=('http://www.ebay.com','http://www.google.com','http://www.nasa.gov');
$b=0;while($b100) { print $b;print@page[$b]; $url = @page[$b];
print This is $url;print @page[$url]; # for instance $ua =
LWP::UserAgent-new;
# Set up a callback that collect image links my @imgs = (); sub callback
{ my($tag, %attr) = @_; return if $tag ne 'a'; # we only look closer
at img ... push(@imgs, values %attr); }
# Make the parser. Unfortunately, we don't know the base yet # (it might
be diffent from $url) $p = HTML::LinkExtor-new(\callback);
# Request document and parse it as it arrives $res =
$ua-request(HTTP::Request-new(GET = $url), sub
{$p-parse($_[0])});
# Expand all image URLs to absolute ones my $base = $res-base; @imgs =
map { $_ = url($_, $base)-abs; } @imgs;
# Print them out print join(\n, @imgs), \n;
print (@imgs[1]);
for($a=0;$a10;$a=$a+1){$ie-gotoURL(@imgs[$a]);print($img);}$b++;}
Any help would be appreciated
Ah, John and Brian will like this one. It has very few lines :)
Rob
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Re: Nested loop
Chas Owens schreef:
But Synopsis 4* says
There is no foreach statement any more. It's always spelled for
in Perl 6,
so it always takes a list as an argument
Well Perl6 isn't Perl, it's a successor to Perl. Like Perl did, Perl6
took a lot of good parts out of other languages (like Perl, Haskell,
Java, etc.) to become the rather perfect language it now is.
Perl6 has far more syntactical synonymity than any language I know. For
example a Perl6Tidy could present your (or someone else's) Perl6 code in
many different verbosities, far beyond all the different ways that
s~^\s+~~, s~\s+$~~ for $text;
could be rewritten into.
$ perl -MO=Deparse -e's#^\s+##, s#\s+$## for $s'
;
foreach $_ ($s) {
s/^\s+//, s/\s+$//;
}
-e syntax OK
--
Affijn, Ruud
Gewoon is een tijger.
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Re: Nested loop
On 4/21/07, Dr.Ruud [EMAIL PROTECTED] wrote: Chas Owens schreef: But Synopsis 4* says There is no foreach statement any more. It's always spelled for in Perl 6, so it always takes a list as an argument Well Perl6 isn't Perl, it's a successor to Perl. Like Perl did, Perl6 took a lot of good parts out of other languages (like Perl, Haskell, Java, etc.) to become the rather perfect language it now is. snip By that reasoning Perl 5 isn't Perl either. Every new major version of Perl has had some pretty radical stuff in it. That said, it is a design goal to let the users still write Perl 5 syntax in a compatibility mode, but if you do that then you miss out on all of the cool stuff like hyperoperators, the new rule based regexes, pointy blocks, etc. -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
Re: Nested loop
Chas Owens schreef: Dr.Ruud: Chas Owens: But Synopsis 4* says There is no foreach statement any more. It's always spelled for in Perl 6, so it always takes a list as an argument Well Perl6 isn't Perl, it's a successor to Perl. Like Perl did, Perl6 took a lot of good parts out of other languages (like Perl, Haskell, Java, etc.) to become the rather perfect language it now is. snip By that reasoning Perl 5 isn't Perl either. Every new major version of Perl has had some pretty radical stuff in it. s/Perl 6/Onion/ http://www.nntp.perl.org/group/perl.perl5.porters/2007/02/msg120600.html Perl 5 can be succeeded by Perl 7 or Kurila: http://www.nntp.perl.org/group/perl.perl5.porters/2007/02/msg121360.html I prefer to go from Perl 5.9.x to Perl5 v10.0. http://groups.google.co.uk/groups/search?q=future.perl.development Perl5 is here to stay. -- Affijn, Ruud Gewoon is een tijger. -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
Re: Nested loop
--- Chas Owens [EMAIL PROTECTED] wrote:
On 4/19/07, John W. Krahn [EMAIL PROTECTED] wrote:
Chas Owens wrote:
Yes, foreach was aliased to for for backwards
compatibility,
Huh? Do you have something to back up that claim?
Well, perlsyn* says
The foreach keyword is actually a synonym
for the for keyword, so
you can use foreach for readability or
for for brevity. (Or
because the Bourne shell is more familiar to
you than csh, so writing
for comes more naturally.)
But Synopsis 4* says
There is no foreach statement any more. It's
always spelled for
in Perl 6,
so it always takes a list as an argument
So, you can either start training yourself to say
for instead of
foreach now or wait for culture shock down the road.
It really does not matter to me which one I use b/c
they both work well and seem to produce the same
results in all my tested code. Its like asking me
would you like that coffee with cream/sugar or black.
ANSWER: I like coffee black and with cream/sugar, it
does not matter much and it all depends upon my mood.
Interesting though I ran perl -MO=Deparse on this
code...
[EMAIL PROTECTED] /cygdrive/c/temp
$ cat foo1
for my $i (0 .. 3) {
$i *= 3;
print $i,\n;
}
print \n\n;
for my $i (map { $_ * 3 } 0 .. 3) {
print $i\n;
}
$ perl -MO=Deparse foo1
foreach my $i (0 .. 3) {
$i *= 3;
print $i, \n;
}
print \n\n;
foreach my $i (map {$_ * 3;} 0..3) {
print $i\n;
}
foo1 syntax OK
So is foreach really dead or going away?
BTW Great write up Chas!
$ perl -v
This is perl, v5.8.7 built for
cygwin-thread-multi-64int
(with 1 registered patch, see perl -V for more detail)
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Re: Nested loop
There's been mentions of efficiency. I'm under the impression that for the uses Perl is put to, the efficiency of a loop is sorta irrelevent. If you are doing harddrive/network access, the performance gain of one loop over the other is more of less invisible. Come to think of it, the time for interpretting got to overshadow the performance gain... For running mathematical stuff, wouldn't you use C? -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
Re: Nested loop
Chas Owens wrote:
On 4/19/07, John W. Krahn [EMAIL PROTECTED] wrote:
Chas Owens wrote:
Yes, foreach was aliased to for for backwards compatibility,
Huh? Do you have something to back up that claim?
Well, perlsyn* says
The foreach keyword is actually a synonym for the for keyword, so
you can use foreach for readability or for for brevity. (Or
because the Bourne shell is more familiar to you than csh, so writing
for comes more naturally.)
But Synopsis 4* says
There is no foreach statement any more. It's always spelled for
in Perl 6,
so it always takes a list as an argument
So, you can either start training yourself to say for instead of
foreach now or wait for culture shock down the road.
I see nothing about backwards compatibility in there? ;-)
but, like
telnet and rsh, it should not be used in new code.
Really? I assume you mean the protocols and not the programs?
The protocols and the programs (unless you are using the telnet
program for manual testing of server protocols).
Yes, the telnet program is a lot more useful than just using the telnet
protocol.
[ snip ]
Which still proves the point, for(;;) is no better than while (1) for
infinite loops. In my opinion while is better since I will eventually
realize that this should not be an infinite loop.
my $continue = 1;
$SIG{__TERM__} = sub { $continue = 0 };
while ($continue} {
}
my $continue = 1;
$SIG{ __TERM__ } = sub { $continue = 0 };
for ( ;$continue; } {
}
John
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Re: Nested loop
yitzle wrote: There's been mentions of efficiency. I'm under the impression that for the uses Perl is put to, the efficiency of a loop is sorta irrelevent. If you are doing harddrive/network access, the performance gain of one loop over the other is more of less invisible. Come to think of it, the time for interpretting got to overshadow the performance gain... For running mathematical stuff, wouldn't you use C? Probably FORTRAN. :-) John -- Perl isn't a toolbox, but a small machine shop where you can special-order certain sorts of tools at low cost and in short order. -- Larry Wall -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
Re: Nested loop
On 4/20/07, yitzle [EMAIL PROTECTED] wrote:
There's been mentions of efficiency.
I'm under the impression that for the uses Perl is put to, the
efficiency of a loop is sorta irrelevent. If you are doing
harddrive/network access, the performance gain of one loop over the
other is more of less invisible.
Come to think of it, the time for interpretting got to overshadow the
performance gain...
I was trying to address all arguments for the use of C-style for. In
general, though, premature optimization is a waste of time. You
should be aware of the general cost of the constructs you use (that is
why I occasionally post benchmarks for alternate algorithms), but you
should be more concerned with making what you write clearly express
your intent. This is why I prefer
my @a = (0 .. 10);
my $i = 0;
for my $elem (grep {not $i++ % 3} @a) {
func($elem);
}
to
for (my $i = 0; $i @a; $i += 3) {
func($a[$i]
}
The grep clearly states that I am looking for something and its block
tells me what the criteria are.
For running mathematical stuff, wouldn't you use C?
Nah, Fortran.
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Re: Nested loop
On 4/20/07, John W. Krahn [EMAIL PROTECTED] wrote:
snip
I see nothing about backwards compatibility in there? ;-)
snip
Nope, I could not find any proof. I did find a merlyn quote on
perlmonks that states for and foreach have always been aliased, but
that is not how I remember it. But who am I to argue with Randal?
snip
my $continue = 1;
$SIG{__TERM__} = sub { $continue = 0 };
while ($continue} {
}
my $continue = 1;
$SIG{ __TERM__ } = sub { $continue = 0 };
for ( ;$continue; } {
}
snip
Yes, it can be done, but which looks better?
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Re: Nested loop
Chas Owens wrote:
On 4/20/07, yitzle [EMAIL PROTECTED] wrote:
There's been mentions of efficiency.
I'm under the impression that for the uses Perl is put to, the
efficiency of a loop is sorta irrelevent. If you are doing
harddrive/network access, the performance gain of one loop over the
other is more of less invisible.
Come to think of it, the time for interpretting got to overshadow the
performance gain...
I was trying to address all arguments for the use of C-style for. In
general, though, premature optimization is a waste of time. You
should be aware of the general cost of the constructs you use (that is
why I occasionally post benchmarks for alternate algorithms), but you
should be more concerned with making what you write clearly express
your intent. This is why I prefer
my @a = (0 .. 10);
my $i = 0;
for my $elem (grep {not $i++ % 3} @a) {
func($elem);
}
to
for (my $i = 0; $i @a; $i += 3) {
func($a[$i]
}
The grep clearly states that I am looking for something and its block
tells me what the criteria are.
You are omitting one critical argument. For people who are stuck with older
versions of Perl and in your grep() example above the foreach expression
creates its list in memory which may cause the program to die if the list is
large enough while the C style for loop does not have this problem.
John
--
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Re: Nested loop
On 4/20/07, John W. Krahn [EMAIL PROTECTED] wrote: snip You are omitting one critical argument. For people who are stuck with older versions of Perl and in your grep() example above the foreach expression creates its list in memory which may cause the program to die if the list is large enough while the C style for loop does not have this problem. snip I refuse to let the fact that some people cannot/will not upgrade their copy of Perl affect how I code or advise others to code. There are still people who wrtie/maintain Perl4 scripts, should I not tell people to use the strict pragma? Even IBM is shipping a modern Perl with AIX now. -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
Re: Nested loop
--- Chas Owens [EMAIL PROTECTED] wrote:
On 4/20/07, John W. Krahn [EMAIL PROTECTED] wrote:
snip
You are omitting one critical argument. For
people who are stuck with older
versions of Perl and in your grep() example above
the foreach expression
creates its list in memory which may cause the
program to die if the list is
large enough while the C style for loop does not
have this problem.
snip
I refuse to let the fact that some people
cannot/will not upgrade
their copy of Perl affect how I code or advise
others to code. There
are still people who wrtie/maintain Perl4 scripts,
should I not tell
people to use the strict pragma? Even IBM is
shipping a modern Perl
with AIX now.
I agree with Chas and can support the AIX notion as I
work on AIX 5.3 machines which is the latest AIX.
But I did not see any response about:
Interesting though I ran perl -MO=Deparse on this
code...
So will foreach really be going away?
$ cat foo1
for my $i (0 .. 3) {
$i *= 3;
print $i,\n;
}
print \n\n;
for my $i (map { $_ * 3 } 0 .. 3) {
print $i\n;
}
$ perl -MO=Deparse foo1
foreach my $i (0 .. 3) {
$i *= 3;
print $i, \n;
}
print \n\n;
foreach my $i (map {$_ * 3;} 0..3) {
print $i\n;
}
foo1 syntax OK
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Re: Nested loop
On Fri, Apr 20, 2007 at 01:47:18PM -0400, Chas Owens wrote:
but you
should be more concerned with making what you write clearly express
your intent. This is why I prefer
my @a = (0 .. 10);
my $i = 0;
for my $elem (grep {not $i++ % 3} @a) {
func($elem);
}
to
for (my $i = 0; $i @a; $i += 3) {
func($a[$i]
}
The grep clearly states that I am looking for something and its block
tells me what the criteria are.
There are times where this list needs webcams. I'd love to have been
able to have seen you as you wrote that since I find it hard to believe
that anyone could have done so whilst keeping a straight face ;-)
I presume that in your second example you should really be comparing
against
for (my $i = 0; $i 10; $i += 3) {
func($i);
}
which just seems so much clearer to me.
Fortunately, TIMTOWTDI, but with any luck I won't be maintaining your
code ;-)
Anyway, there seems to be a little confusion about whether for or
foreach were going to be removed from the language. The main point I
wanted to make was that foreach is not going away. Neither is for. At
least, not in Perl5, which will still be around for a long time. They
are still synonyms, and any code written now and using either of these
constructs will continue to work under all Perl5 releases.
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Re: Nested loop
On 4/20/07, oryann9 [EMAIL PROTECTED] wrote:
snip
So will foreach really be going away?
snip
If Synopsis 4* is to be believed, in Perl 6 there will not be a loop
named foreach. There will be a loop named for that does the has all
of the functionality of foreach (just like in Perl 5). Also the for
loop will not have the C-style functionality. A new loop named loop
will have that functionality.
So the Perl 5 code
foreach my $elem (@array) {}
for (my $i = 0; $i 10; $i += 3) {}
will in Perl 6 become
for @array - $elem {}
loop ($i = 0; $i 10; $i += 3) {}
Note that the loop construct could also be written like this
for 0 .. 10 : by 3 - $i {}
I am not aware of any targeted release date for Perl 6 (other than
when it is done), so you still have plenty of time with foreach to
say your goodbyes, but I would note that many things from Perl 6 are
coming early in perl 5.10: say, given/when, // (like ||, but tests for
undef, not false), err (like or, but tests for undef not false), and
~~ (replaces and extends =~).
* http://dev.perl.org/perl6/doc/design/syn/S04.html
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Re: Nested loop
On 4/20/07, Paul Johnson [EMAIL PROTECTED] wrote:
snip
The grep clearly states that I am looking for something and its block
tells me what the criteria are.
There are times where this list needs webctams. I'd love to have been
able to have seen you as you wrote that since I find it hard to believe
that anyone could have done so whilst keeping a straight face ;-)
No, I really do think it is better code that expresses the intent;
however, I don't like the goal behind code in the first place. How
often do you take each third element of list? If you are doing that
then you are most likely doing something else wrong farther up in your
code.
I presume that in your second example you should really be comparing
against
for (my $i = 0; $i 10; $i += 3) {
func($i);
}
which just seems so much clearer to me.
if your goal is to produce 0, 3, 6, and 9 then yes, it is somewhat
clearer, but the very fact the you have a 10 there instead of a 9
points to the off-by-one errors that tend to plague the C-style for
loop. Unfortunately we will have to wait until Perl 6 for the better
solution:
for 0 .. 9 : by 3 - $i {}
Fortunately, TIMTOWTDI, but with any luck I won't be maintaining your
code ;-)
I probably wouldn't write that code. I would fix whatever was causing
me to have to take every third element of a list.
Anyway, there seems to be a little confusion about whether for or
foreach were going to be removed from the language. The main point I
wanted to make was that foreach is not going away. Neither is for. At
least, not in Perl5, which will still be around for a long time. They
are still synonyms, and any code written now and using either of these
constructs will continue to work under all Perl5 releases.
The trend going forward is to do away with foreach in favor of for, so
the question becomes is there any good reason to type four more
letters?
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Re: Nested loop
Chas Owens schreef: foreach is dead, long live for. I am in favor of burying foreach as well, bu I see that many people still like to use for for the C-style construct, and foreach for the other one. -- Affijn, Ruud Gewoon is een tijger. -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
Re: Nested loop
From: Chas Owens [EMAIL PROTECTED]
On 4/18/07, yitzle [EMAIL PROTECTED] wrote:
I got an array of hashes so I am using a foreach (@arr) loop to access
the hashes.
How do I go about looping through the hash's keys/values? I was
thinking of another foreach, but then the $_ gets a bit screwed up...
Do I need to do this ?
foreach(@arr) {
%hash = %{$_};
foreach (keys %hash) {
print $_ = $hash{$_}\n;
}
}
foreach is dead, long live for.
William is dead, long live Bill?
foreach and for are two names for the same thing and just as you can
call someone both William and Bill you can use foreach and for
interchangeably.
foreach(my $i = 0; $i $whatever; $i++)
for(my $i = 0; $i $whatever; $i++)
for my $x (@array)
foreach my $x (@array)
for (@array)
foreach (@array)
No difference to the computer. Use whichever reads best!
I would myself use for for the C-style loops and if I use the loop
as a way to create an alias
for ($data-{$key}[1]{whatever}{booo}) {
s/.../.../g;
s/.../.../g;
if (/.../) {
$_ = $3-$2-$1
}
}
or
for my $text ($data-{$key}[1]{whatever}{booo}) {
$text =~ s/.../.../g;
$text = foolify($text, $sumfin);
}
and foreach is I need to loop through a collection (array, list,
keys or values of a hash, ...). Though I don't think I'm 100%
consistent in this.
Jenda
= [EMAIL PROTECTED] === http://Jenda.Krynicky.cz =
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to get drunk and croon as much as they like.
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Re: Nested loop
On 4/19/07, Jenda Krynicky [EMAIL PROTECTED] wrote:
From: Chas Owens [EMAIL PROTECTED]
snip
foreach is dead, long live for.
William is dead, long live Bill?
foreach and for are two names for the same thing and just as you can
call someone both William and Bill you can use foreach and for
interchangeably.
foreach(my $i = 0; $i $whatever; $i++)
for(my $i = 0; $i $whatever; $i++)
for my $x (@array)
foreach my $x (@array)
for (@array)
foreach (@array)
No difference to the computer. Use whichever reads best!
Yes, foreach was aliased to for for backwards compatibility, but, like
telnet and rsh, it should not be used in new code.
I would myself use for for the C-style loops
And this is why. As long as people think well, I have foreach which
is for iterating and for which is for C-style loops they will
continue to write C-style loops. C-style loops are bad. They are
there for backwards compatibility. I can't think of a single for loop
that isn't better written as a range based for loop or while loop. For
instance
standard range based loop
for (my $i = 0; $i 10; $i++) {}
for my $i (0 .. 9) {}
often $i winds up being used as an index which just makes me cringe.
The infinite loop
for (;;) {}
while (1) {}
The reason C programmers give for using for (;;) is that it generates
less overhead on their platform, but, at least with my tests*,
while(1) is more efficient in Perl.
Weirder stuff that you only tend to see people coming from a C background do
for (my $node = $head; $node = $node; $node-next) {}
my $node = $head;
while ($node = $node-next) {}
But in Perl it is rarely necessary to do this sort of loop since most
functions return a list that can be iterated over using for:
for my $node ($head-nodes) {}
and if I use the for loop as a way to create an alias
And that is a perfectly idiomatic usage; at least until given is added
to the language (in 5.10 from what I hear).
* benchmark
Rate bare for while
bare 6754/s-- -17% -31%
for 8179/s 21%-- -17%
while 9823/s 45% 20%--
#!/usr/bin/perl
use strict;
use warnings;
use Benchmark;
my %subs = (
for = sub { my $i; for (;;) { last if $i++ 1_000 } },
while = sub { my $i; while (1) { last if $i++ 1_000 } },
bare = sub { my $i; { last if $i++ 1_000; redo } },
);
Benchmark::cmpthese(-10, \%subs);
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Re: Nested loop
foreach is dead?
dangit... I loved that.
and, java 5 just put in a for loop construct that is very similar to the
foreach.
jen
On Thursday, April 19, 2007, at 08:08AM, Chas Owens [EMAIL PROTECTED] wrote:
On 4/19/07, Jenda Krynicky [EMAIL PROTECTED] wrote:
From: Chas Owens [EMAIL PROTECTED]
snip
foreach is dead, long live for.
William is dead, long live Bill?
foreach and for are two names for the same thing and just as you can
call someone both William and Bill you can use foreach and for
interchangeably.
foreach(my $i = 0; $i $whatever; $i++)
for(my $i = 0; $i $whatever; $i++)
for my $x (@array)
foreach my $x (@array)
for (@array)
foreach (@array)
No difference to the computer. Use whichever reads best!
Yes, foreach was aliased to for for backwards compatibility, but, like
telnet and rsh, it should not be used in new code.
I would myself use for for the C-style loops
And this is why. As long as people think well, I have foreach which
is for iterating and for which is for C-style loops they will
continue to write C-style loops. C-style loops are bad. They are
there for backwards compatibility. I can't think of a single for loop
that isn't better written as a range based for loop or while loop. For
instance
standard range based loop
for (my $i = 0; $i 10; $i++) {}
for my $i (0 .. 9) {}
often $i winds up being used as an index which just makes me cringe.
The infinite loop
for (;;) {}
while (1) {}
The reason C programmers give for using for (;;) is that it generates
less overhead on their platform, but, at least with my tests*,
while(1) is more efficient in Perl.
Weirder stuff that you only tend to see people coming from a C background do
for (my $node = $head; $node = $node; $node-next) {}
my $node = $head;
while ($node = $node-next) {}
But in Perl it is rarely necessary to do this sort of loop since most
functions return a list that can be iterated over using for:
for my $node ($head-nodes) {}
and if I use the for loop as a way to create an alias
And that is a perfectly idiomatic usage; at least until given is added
to the language (in 5.10 from what I hear).
* benchmark
Rate bare for while
bare 6754/s-- -17% -31%
for 8179/s 21%-- -17%
while 9823/s 45% 20%--
#!/usr/bin/perl
use strict;
use warnings;
use Benchmark;
my %subs = (
for = sub { my $i; for (;;) { last if $i++ 1_000 } },
while = sub { my $i; while (1) { last if $i++ 1_000 } },
bare = sub { my $i; { last if $i++ 1_000; redo } },
);
Benchmark::cmpthese(-10, \%subs);
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Re: Nested loop
Chas Owens wrote:
On 4/19/07, Jenda Krynicky [EMAIL PROTECTED] wrote:
From: Chas Owens [EMAIL PROTECTED]
snip
foreach is dead, long live for.
William is dead, long live Bill?
foreach and for are two names for the same thing and just as you can
call someone both William and Bill you can use foreach and for
interchangeably.
foreach(my $i = 0; $i $whatever; $i++)
for(my $i = 0; $i $whatever; $i++)
for my $x (@array)
foreach my $x (@array)
for (@array)
foreach (@array)
No difference to the computer. Use whichever reads best!
Yes, foreach was aliased to for for backwards compatibility,
Huh? Do you have something to back up that claim?
but, like
telnet and rsh, it should not be used in new code.
Really? I assume you mean the protocols and not the programs?
I would myself use for for the C-style loops
And this is why. As long as people think well, I have foreach which
is for iterating and for which is for C-style loops they will
continue to write C-style loops. C-style loops are bad. They are
there for backwards compatibility. I can't think of a single for loop
that isn't better written as a range based for loop or while loop. For
instance
standard range based loop
for (my $i = 0; $i 10; $i++) {}
for my $i (0 .. 9) {}
How about:
for ( my $i = 0; $i 10; $i += 3 ) {}
foreach my $i ( ? .. ? ) {}
often $i winds up being used as an index which just makes me cringe.
The infinite loop
for (;;) {}
while (1) {}
The reason C programmers give for using for (;;) is that it generates
less overhead on their platform, but, at least with my tests*,
while(1) is more efficient in Perl.
I ran your benchmark on my computer and for(;;) and while(1) ran at about the
same speed.
$ perl -le'
use Benchmark;
my %subs = (
for = sub { my $i; for (;;) { last if $i++ 1_000 } },
while = sub { my $i; while (1) { last if $i++ 1_000 } },
bare = sub { my $i; { last if $i++ 1_000; redo } },
);
Benchmark::cmpthese(-10, \%subs);
'
Rate bare for while
bare 4471/s-- -15% -15%
for 5253/s 17%-- -0%
while 5268/s 18%0%--
$ perl -le'
use Benchmark;
my %subs = (
for = q{ my $i; for (;;) { last if $i++ 1_000 } },
while = q{ my $i; while (1) { last if $i++ 1_000 } },
bare = q{ my $i; { last if $i++ 1_000; redo } },
);
Benchmark::cmpthese(-10, \%subs);
'
Rate bare while for
bare 4445/s-- -15% -15%
while 5219/s 17%-- -0%
for 5233/s 18%0%--
John
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Re: Nested loop
John W. Krahn wrote:
Chas Owens wrote:
On 4/19/07, Jenda Krynicky [EMAIL PROTECTED] wrote:
From: Chas Owens [EMAIL PROTECTED]
foreach is dead, long live for.
I would myself use for for the C-style loops
And this is why. As long as people think well, I have foreach which
is for iterating and for which is for C-style loops they will
continue to write C-style loops. C-style loops are bad. They are
there for backwards compatibility. I can't think of a single for loop
that isn't better written as a range based for loop or while loop. For
instance
standard range based loop
for (my $i = 0; $i 10; $i++) {}
for my $i (0 .. 9) {}
How about:
for ( my $i = 0; $i 10; $i += 3 ) {}
foreach my $i ( ? .. ? ) {}
And
for (my $elem = $doc-firstChild; $elem; $elem = $elem-nextSibling) {
:
}
Rob
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Re: Nested loop
On 4/19/07, John W. Krahn [EMAIL PROTECTED] wrote:
Chas Owens wrote:
Yes, foreach was aliased to for for backwards compatibility,
Huh? Do you have something to back up that claim?
Well, perlsyn* says
The foreach keyword is actually a synonym for the for keyword, so
you can use foreach for readability or for for brevity. (Or
because the Bourne shell is more familiar to you than csh, so writing
for comes more naturally.)
But Synopsis 4* says
There is no foreach statement any more. It's always spelled for
in Perl 6,
so it always takes a list as an argument
So, you can either start training yourself to say for instead of
foreach now or wait for culture shock down the road.
but, like
telnet and rsh, it should not be used in new code.
Really? I assume you mean the protocols and not the programs?
The protocols and the programs (unless you are using the telnet
program for manual testing of server protocols).
I would myself use for for the C-style loops
And this is why. As long as people think well, I have foreach which
is for iterating and for which is for C-style loops they will
continue to write C-style loops. C-style loops are bad. They are
there for backwards compatibility. I can't think of a single for loop
that isn't better written as a range based for loop or while loop. For
instance
standard range based loop
for (my $i = 0; $i 10; $i++) {}
for my $i (0 .. 9) {}
How about:
for ( my $i = 0; $i 10; $i += 3 ) {}
foreach my $i ( ? .. ? ) {}
for my $i (0 .. 3) {
$i *= 3;
}
for my $i (map { $_ * 3 } 0 .. 3) {
print $i\n;
}
The bigger question is why is the end condition 10? Did you intend to
include it the list? Are you making an off by one error? This is why
the C-style for loop is bad.
A better phrasing would be:
my @a = (0 .. 10);
for (my $i = 0; $i @a; $i += 3) { func($a[$i])}
This is much harder to move away from the C-style for loop. I also
can't think of the last time I needed to do it.
Hmm, the naive implementation is not bad, it communicates the intent
a little better in my mind, but I don't like it.
my @a = (0 .. 10);
my $i = 0;
for my $elem (@a) {
next if $i++ % 3;
func($elem);
}
I think this solution communicates the intent best.
my @a = (0 .. 10);
my $i = 0;
for my $elem (grep {not $i++ % 3} @a) {
func($elem);
}
In Perl 6 we will have better options.
I don't like this one, it seems too kludgey
for @a - $elem, undef, undef { func($elem) }
This one is only a little better than the Perl 5 variant
for each(@a ; 0 .. *) - $elem, $i {
next if $i % 3;
func($elem)
}
Of course, there is the C-style for loop in disguise
loop ($i = 0; $i @a; $i += 3) { func($a[$i]) }
This looks the C-style for loop in disguise
for 0 .. $#a : by(3) - $i { func($a[$i]) }
But with a little tweak I think it is the best of all
for @a[0 .. $#a : by(3)] - $elem { func($elem) }
often $i winds up being used as an index which just makes me cringe.
The infinite loop
for (;;) {}
while (1) {}
The reason C programmers give for using for (;;) is that it generates
less overhead on their platform, but, at least with my tests*,
while(1) is more efficient in Perl.
I ran your benchmark on my computer and for(;;) and while(1) ran at about the
same speed.
Which still proves the point, for(;;) is no better than while (1) for
infinite loops. In my opinion while is better since I will eventually
realize that this should not be an infinite loop.
my $continue = 1;
$SIG{__TERM__} = sub { $continue = 0 };
while ($continue} {
}
* http://perldoc.perl.org/perlsyn.html
* http://dev.perl.org/perl6/doc/design/syn/S04.html
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Re: Nested loop
On 4/19/07, Rob Dixon [EMAIL PROTECTED] wrote:
snip
for (my $elem = $doc-firstChild; $elem; $elem = $elem-nextSibling) {
:
}
snip
I covered that in my earlier email:
Weirder stuff that you only tend to see people coming from a C background do
for (my $node = $head; $node;$node = $node-next) {}
...
But in Perl it is rarely necessary to do this sort of loop since most
functions return a list that can be iterated over using for:
for my $node ($head-nodes) {}
In this case your module should include a children method
for my $elem ($doc-children) {}
or a true iterator
my $iter = $doc-child_iter;
while (my $elem = $iter-next) {}
If it doesn't then bug the maintainer to add one or both. Having a
true iterator will put him or her ahead of the curve for Perl 6's
iterated-the-iterator operator
for =$iter - $elem {}
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Re: Nested loop
On 4/18/07, yitzle [EMAIL PROTECTED] wrote:
I got an array of hashes so I am using a foreach (@arr) loop to access
the hashes.
How do I go about looping through the hash's keys/values? I was
thinking of another foreach, but then the $_ gets a bit screwed up...
Do I need to do this ?
foreach(@arr) {
%hash = %{$_};
foreach (keys %hash) {
print $_ = $hash{$_}\n;
}
}
foreach is dead, long live for.
Use named values in your for loop:
for my $h (@arr) {
for my $key (sort keys %$h) {
print $key = $h-{$key}\n
}
}
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Re: Nested loop
On 4/18/07, yitzle [EMAIL PROTECTED] wrote:
I got an array of hashes so I am using a foreach (@arr) loop to access
the hashes.
How do I go about looping through the hash's keys/values? I was
thinking of another foreach, but then the $_ gets a bit screwed up...
Do I need to do this ?
foreach(@arr) {
%hash = %{$_};
foreach (keys %hash) {
print $_ = $hash{$_}\n;
}
}
This is a good time to avoid the foreach loop's default control
variable. Although $_ is handy for small loops, larger (and nested)
ones should generally name another control variable. By giving a name
to the control variable, you should be able to access the hash without
copying the data to another %hash variable. Perl even has special
syntax you can use if the reference is in a scalar variable. It can
even be a 'my' variable:
my @arr = ( # just some sample hash references
{ qw/ fred flintstone barney rubble wilma flintstone betty rubble / },
{ qw/ 4 ! 2 potato 3 potato 1 potato / },
{ qw/ 4 gotten 2 cool /, '2 ', 'B' },
);
foreach my $href (@arr) {
foreach (sort keys %$href) {
print $_ = $href-{$_}\n;
}
print \n;
}
Hope this helps!
--Tom Phoenix
Stonehenge Perl Training
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Re: Nested Loop
- Original Message -
From: [EMAIL PROTECTED]
Date: Thursday, January 19, 2006 3:19 pm
Subject: Nested Loop
Greetings,
Hello
Basically I deleted a portion of a mysql database and need to
insert the
subnet back in. The output is suppose to increment the first
field
starting with '8' until the IP is 10.168.17.255. I can't figure
out my
inside loops condition.
You have a Typo Sir.
Maybe there is a perl module for this?
Example:
INSERT INTO `anyInventory_values` VALUES (8,1,'10.168.17.0');
INSERT INTO `anyInventory_values` VALUES (8,2,'Unknown');
INSERT INTO `anyInventory_values` VALUES (8,3,'');
INSERT INTO `anyInventory_values` VALUES (8,4,'');
INSERT INTO `anyInventory_values` VALUES (8,5,'');
INSERT INTO `anyInventory_values` VALUES (8,6,'');
INSERT INTO `anyInventory_values` VALUES (8,7,'');
INSERT INTO `anyInventory_values` VALUES (8,8,'Unknown');
INSERT INTO `anyInventory_values` VALUES (8,9,'');
INSERT INTO `anyInventory_values` VALUES (8,10,'');
INSERT INTO `anyInventory_values` VALUES (8,14,'');
INSERT INTO `anyInventory_values` VALUES (9,1,'10.168.17.1');
INSERT INTO `anyInventory_values` VALUES (9,2,'Unknown');
INSERT INTO `anyInventory_values` VALUES (9,3,'');
INSERT INTO `anyInventory_values` VALUES (9,4,'');
INSERT INTO `anyInventory_values` VALUES (9,5,'');
INSERT INTO `anyInventory_values` VALUES (9,6,'');
INSERT INTO `anyInventory_values` VALUES (9,7,'');
INSERT INTO `anyInventory_values` VALUES (9,8,'Unknown');
INSERT INTO `anyInventory_values` VALUES (9,9,'');
INSERT INTO `anyInventory_values` VALUES (9,10,'');
INSERT INTO `anyInventory_values` VALUES (9,14,'');
...
My Runaway Perl Script:
$file = 'out.sql'; # sql script
open(INFO, $file); # open for output
for($x=0;$x=255;$x++){
for($n=8;$n+1;$n++){
There is no terminated condition here, you probably wanted to say
for($n=1;$n=8;$n++){
Alternative would be
for my $n (1...8){
print INFO INSERT INTO \`anyInventory_values\` VALUES
($n,1,'10.168.17.$x')\;\n;
print INFO INSERT INTO \`anyInventory_values\` VALUES
($n,2,'Unknown')\;\n;
print INFO INSERT INTO \`anyInventory_values\` VALUES
($n,3,'')\;\n;
print INFO INSERT INTO \`anyInventory_values\` VALUES
($n,4,'')\;\n;
print INFO INSERT INTO \`anyInventory_values\` VALUES
($n,5,'')\;\n;
print INFO INSERT INTO \`anyInventory_values\` VALUES
($n,6,'')\;\n;
print INFO INSERT INTO \`anyInventory_values\` VALUES
($n,7,'')\;\n;
print INFO INSERT INTO \`anyInventory_values\` VALUES
($n,8,'Unknown')\;\n;
print INFO INSERT INTO \`anyInventory_values\` VALUES
($n,9,'')\;\n;
print INFO INSERT INTO \`anyInventory_values\` VALUES
($n,10,'')\;\n;
print INFO INSERT INTO \`anyInventory_values\` VALUES
($n,14,'')\;\n;
}
}
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Re: nested replace string
Please help me in where I am going wrong and suggest me the solution. Since you have the data in nice XML format, why not use an XML parser instead of parsing it yourself? http://perl-xml.sourceforge.net/faq/ -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
Re: nested if
No, your post was not in the last e-mail digest I received, unless I
missed it somehow? But the link you provided seems to clear things up
for me. So, it's not about the order of operation but the timing of
when the variables actually get defined.
That is, during the beginning of the loop since the values are not
defined then they are ignored. When the loop proceeds again these
values (at this point) are now defined because of the previous
iteration of the loop has set the values from the else statement?
-Mike
On Jul 2, 2004, at 10:25 PM, Michael S. Robeson II wrote:
Well yeah, the indentation makes it much more clearer. However, this
does not help me understand how the nested if statements are
working. Which of the two if statements gets evaluated first? I am
trying to figure out in english what the if statements are
actually doing. Is it saying:
If a line begins with bla-bla and if $seq (which appears no
where else in the code other than $seq= ) exists assign it to the
hash pro with the name bla-bla.
So my question is how does the inner if statement work when seq= is
out side that if statement?
Is the outer if statement evaluated first then the inner? Because
how does the inner if statement know what $seq is?
I am probably not making any sense but I am trying to figure out
mechanically how the perl interpreter knows what to do in the context
of the nested if statements.
-Thanks
-Mike
Gunnar Hjalmarsson wrote:
That illustrates the importance of indenting the code in a way that
makes sense:
while (align) {
$line=$_;
if ($line=~/^(.+)/) {
if ($seq) {
$pro{$name}=$seq;
#print SEQ:\n$pro\n\n;
}
$name=$1;
$name=~s/\s//g;
push @names, $name;
#print $name\n;
$k++;
$seq=;
} else {
chomp $line;
$seq.=$line;
}
}
Quite a difference, isn't it?
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Re: nested if
Great, thanks for the help! -Mike On Jul 3, 2004, at 2:16 PM, Gunnar Hjalmarsson wrote: Michael S. Robeson II wrote: No, your post was not in the last e-mail digest I received, I see. Sometimes I think that digest mode for mailing lists is a nuisance. ;-) But the link you provided seems to clear things up for me. So, it's not about the order of operation but the timing of when the variables actually get defined. That is, during the beginning of the loop since the values are not defined then they are ignored. When the loop proceeds again these values (at this point) are now defined because of the previous iteration of the loop has set the values from the else statement? Yep, that's it. I would suggest that you to post the above comment to the list, too. Rgds, Gunnar -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
Re: nested if
Well yeah, the indentation makes it much more clearer. However, this
does not help me understand how the nested if statements are working.
Which of the two if statements gets evaluated first? I am trying to
figure out in english what the if statements are actually doing. Is
it saying:
If a line begins with bla-bla and if $seq (which appears no
where else in the code other than $seq= ) exists assign it to the
hash pro with the name bla-bla.
So my question is how does the inner if statement work when seq= is
out side that if statement?
Is the outer if statement evaluated first then the inner? Because
how does the inner if statement know what $seq is?
I am probably not making any sense but I am trying to figure out
mechanically how the perl interpreter knows what to do in the context
of the nested if statements.
-Thanks
-Mike
Gunnar Hjalmarsson wrote:
That illustrates the importance of indenting the code in a way that
makes sense:
while (align) {
$line=$_;
if ($line=~/^(.+)/) {
if ($seq) {
$pro{$name}=$seq;
#print SEQ:\n$pro\n\n;
}
$name=$1;
$name=~s/\s//g;
push @names, $name;
#print $name\n;
$k++;
$seq=;
} else {
chomp $line;
$seq.=$line;
}
}
Quite a difference, isn't it?
--
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Re: nested if
On 7/2/2004 10:25 PM, Michael S. Robeson II wrote:
Well yeah, the indentation makes it much more clearer. However, this
does not help me understand how the nested if statements are working.
Which of the two if statements gets evaluated first? I am trying to
figure out in english what the if statements are actually doing. Is
it saying:
If a line begins with bla-bla and if $seq (which appears no
where else in the code other than $seq= ) exists assign it to the
hash pro with the name bla-bla.
So my question is how does the inner if statement work when seq= is
out side that if statement?
Is the outer if statement evaluated first then the inner? Because
how does the inner if statement know what $seq is?
I am probably not making any sense but I am trying to figure out
mechanically how the perl interpreter knows what to do in the context of
the nested if statements.
Tidied up a little more:
my( %pro, @names);
my( $name, $seq, $k );
while (defined( my $line = DATA )) {
if ($line =~ /^(.+)/) {
if ($seq) {
$pro{$name} = $seq;
$seq = '';
}
$name = $1;
$name =~ s/\s//g;
push @names, $name;
$k++;
} else {
chomp( $line );
$seq .= $line;
}
}
This code deals with multi-line sequences, putting multiple lines
together untill a sequence is complete. The 'else' part of the outter
'if' does the accumulation of multiple lines into a sequence. The 'if'
part determines that a sequence is complete, captures some type of name
from the sequence, stores the complete sequence in the '%pro' hash, and
pushes the name onto a '@names' array. I'm guessing '$k' keeps tally of
the number of sequences; it's not clear if that is neccessary since
`scalar @names` possibly will provide the same info. It's also unclear
why there is a '@names' array that mostly duplicates `keys %pro`
I think where you're-understandably-getting confused is that most of
those variables are global. That's made more explicit in my strictified
rewrite above. It could probably be rewritten better if we knew the
exact format of the data being read.
Randy.
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Re: nested if
On 7/3/2004 4:38 AM, Randy W. Sims wrote:
Tidied up a little more:
Actually, I'd probably invert the condition to make it clearer that it's
accumulating multi-line sequences.
my( %pro, @names);
my( $name, $seq, $k );
while (defined( my $line = DATA )) {
unless ($line =~ /^(.+)/) {
chomp( $line );
$seq .= $line;
} else {
if ($seq) {
$pro{$name} = $seq;
$seq = '';
}
($name = $1) =~ s/\s//g;
push @names, $name;
$k++;
}
}
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Re: nested if
Michael S. Robeson II wrote: Which of the two if statements gets evaluated first? I am trying to figure out in english what the if statements are actually doing. Is it saying: If a line begins with bla-bla and if $seq (which appears no where else in the code other than $seq= ) exists assign it to the hash pro with the name bla-bla. So my question is how does the inner if statement work when seq= is out side that if statement? It's a while loop. For a particular iteration of the loop, $seq and $name may contain values that were assigned to them during a *previous* iteration, but the values that will be used in the inner if-statement during the *current* iteration is not related to what will happen to those variables later during this same iteration. Is the outer if statement evaluated first then the inner? As long as we are talking about the same iteration: No. Because how does the inner if statement know what $seq is? See above. HTH -- Gunnar Hjalmarsson Email: http://www.gunnar.cc/cgi-bin/contact.pl -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
Re: nested if
Ok, that make much more sense - I think. So, I guess, the outer 'if'
and 'else' statements get evaluated first. Then the inner 'if' can
proceed once all the lines of data were gathered in the outer 'else'
statement. This way the lines can be assigned as a key-value pair in
the hash. I guess the individual who wrote the code could make it much
cleaner or easier to read. The re-organizing of the conditionals in
your second e-mail makes it perfectly clear and would be something I
would have done had I known how the nested 'if' statement was working
(again if I have right). Hopefully, I 'got it' now. I can see why many
coders are annoyed with nested if statements. :-)
-Thanks!
-Mike
On Jul 3, 2004, at 4:38 AM, Randy W. Sims wrote:
On 7/2/2004 10:25 PM, Michael S. Robeson II wrote:
Well yeah, the indentation makes it much more clearer. However, this
does not help me understand how the nested if statements are
working. Which of the two if statements gets evaluated first? I am
trying to figure out in english what the if statements are
actually doing. Is it saying:
If a line begins with bla-bla and if $seq (which appears no
where else in the code other than $seq= ) exists assign it to
the hash pro with the name bla-bla.
So my question is how does the inner if statement work when seq= is
out side that if statement?
Is the outer if statement evaluated first then the inner? Because
how does the inner if statement know what $seq is?
I am probably not making any sense but I am trying to figure out
mechanically how the perl interpreter knows what to do in the context
of the nested if statements.
Tidied up a little more:
my( %pro, @names);
my( $name, $seq, $k );
while (defined( my $line = DATA )) {
if ($line =~ /^(.+)/) {
if ($seq) {
$pro{$name} = $seq;
$seq = '';
}
$name = $1;
$name =~ s/\s//g;
push @names, $name;
$k++;
} else {
chomp( $line );
$seq .= $line;
}
}
This code deals with multi-line sequences, putting multiple lines
together untill a sequence is complete. The 'else' part of the outter
'if' does the accumulation of multiple lines into a sequence. The 'if'
part determines that a sequence is complete, captures some type of
name from the sequence, stores the complete sequence in the '%pro'
hash, and pushes the name onto a '@names' array. I'm guessing '$k'
keeps tally of the number of sequences; it's not clear if that is
neccessary since `scalar @names` possibly will provide the same info.
It's also unclear why there is a '@names' array that mostly duplicates
`keys %pro`
I think where you're-understandably-getting confused is that most of
those variables are global. That's made more explicit in my
strictified rewrite above. It could probably be rewritten better if we
knew the exact format of the data being read.
Randy.
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Re: nested if
Michael S. Robeson II wrote:
I came across some code on the internet that looks like this (this
is only part of the script):
while (align) {
$line=$_;
if ($line=~/^(.+)/) {
if ($seq) {
$pro{$name}=$seq;
#print SEQ:\n$pro\n\n;
}
$name=$1;
$name=~s/\s//g;
push @names, $name;
#print $name\n;
$k++;
$seq=;
}
else {
chomp $line;
$seq.=$line;
}
}
I am having trouble figuring out how the nested if statements
work (i.e. what is the order of operation etc...) and their
associated else statements.
That illustrates the importance of indenting the code in a way that
makes sense:
while (align) {
$line=$_;
if ($line=~/^(.+)/) {
if ($seq) {
$pro{$name}=$seq;
#print SEQ:\n$pro\n\n;
}
$name=$1;
$name=~s/\s//g;
push @names, $name;
#print $name\n;
$k++;
$seq=;
} else {
chomp $line;
$seq.=$line;
}
}
Quite a difference, isn't it?
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Re: Nested {}
On 6/29/2004 9:58 PM, David Arnold wrote:
All,
Suppose I have a number of lines in a latex file like this:
\backans{If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can substitute
to find a solution.}
I'd like to scan the file and replace all of these with this format:
\begin{answer}
If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can substitute
to find a solution.
\end{answer}
I'm looking for suggestions as to how to make this change with my perl
script. I am puzzled by the use of nested braces and how I can be sure I've
got everything between the opening and closing brace.
You may want to take a look at Text::Balanced or Regexp::Common (the
Regexp::Common::balanced subclass).
For this type of work though, I generally prefer the more
straightforward method of walking thru the file one char at a time,
counting opening braces and substracting closing braces until the count
reaches zero. At that point you can take the appropriate action. For
this task, I really don't believe regexs offer any advantage and are
probably slower (I'm sure Japhy will correct me if I'm wrong here).
Randy.
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Re: Nested {}
Japhy,
Thanks. These suggestions worked great!
At 01:18 AM 6/30/04 -0400, you wrote:
On Jun 29, David Arnold said:
\backans{If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can substitute
to find a solution.}
I'd like to scan the file and replace all of these with this format:
\begin{answer}
If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can substitute
to find a solution.
\end{answer}
To match nested things, you probably want to use Regexp::Common, which
allows you to do that very easily:
use Regexp::Common;
$text =~ s
\\ backans {
( $RE{balanced}{-parens='{}'} )
}
\\begin{answer}\n$1\n\\end{answer}xg;
The /x modifier is so that I can have extra whitespace, and the /g
modifier means do it globally. The %RE hash is quite magical -- see the
Regexp::Common docs for an explanation. The module isn't standard,
though, so you'd have to download it from CPAN yourself.
If you want a stand-alone solution, you can have one if you make use of
some of Perl's special regex constructs:
my $rx; # must be declared first...
$rx = qr[
(?:
(? [^{}\\]+ | \\. )
|
{ (??{ $rx }) }
)*
]xs;
$text =~ s/\\backans{($rx)}/\\begin{answer}\n$1\n\\end{answer}/g;
Its primary trick is the (??{ ... }) assertion, which evaluates its
contents as PART of the regex to match. Since its contents are $rx
itself, it basically creates an automatically deeply-enough nested regex
for you on the fly.
--
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RPI Acacia brother #734 http://www.perlmonks.org/ http://www.cpan.org/
CPAN ID: PINYAN[Need a programmer? If you like my work, let me know.]
stu what does y/// stand for? tenderpuss why, yansliterate of course.
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RE: Nested {}
David Arnold [EMAIL PROTECTED] wrote:
: Suppose I have a number of lines in a latex file like this:
:
: \backans{If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can
: substitute to find a solution.}
:
: I'd like to scan the file and replace all of these with
: this format:
:
: \begin{answer}
: If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can substitute
: to find a solution.
: \end{answer}
:
: I'm looking for suggestions as to how to make this change
: with my perl script. I am puzzled by the use of nested
: braces and how I can be sure I've got everything between
: the opening and closing brace.
As long as the lines do not wrap, you don't need to
worry about the nesting. Perl regexes are greedy by
default. So '.+' will try to suck in the longest match
possible. Which is just what you want.
while ( DATA ) {
printf \\begin{answer}\n%s\n\\end{answer}\n, $1 if /^\\backans{(.+)}/;
}
__END__
\backans{If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can ...}
\backans{If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can ...}
\backans{If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can ...}
\backans{If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can ...}
HTH,
Charles K. Clarkson
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RE: Nested {}
Charles,
Very nice indeed. I learned a lot with your example. Unfortunately, there
are a lot of situations where the lines wrap.
For example,
\backans{Now is the time for all good men to
come to the aid of their country. The domain of
$f(x)=\sqrt{2x+3}$ is $\{x:\,x\ge -3/2\}$.}
Do you have similar good advice for the wrapping situation?
At 09:18 PM 6/29/04 -0500, Charles K. Clarkson wrote:
David Arnold [EMAIL PROTECTED] wrote:
: Suppose I have a number of lines in a latex file like this:
:
: \backans{If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can
: substitute to find a solution.}
:
: I'd like to scan the file and replace all of these with
: this format:
:
: \begin{answer}
: If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can substitute
: to find a solution.
: \end{answer}
:
: I'm looking for suggestions as to how to make this change
: with my perl script. I am puzzled by the use of nested
: braces and how I can be sure I've got everything between
: the opening and closing brace.
As long as the lines do not wrap, you don't need to
worry about the nesting. Perl regexes are greedy by
default. So '.+' will try to suck in the longest match
possible. Which is just what you want.
while ( DATA ) {
printf \\begin{answer}\n%s\n\\end{answer}\n, $1 if /^\\backans{(.+)}/;
}
__END__
\backans{If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can ...}
\backans{If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can ...}
\backans{If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can ...}
\backans{If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can ...}
HTH,
Charles K. Clarkson
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Re: Nested {}
On Jun 29, David Arnold said:
\backans{If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can substitute
to find a solution.}
I'd like to scan the file and replace all of these with this format:
\begin{answer}
If $x=y^{2n}$ and $z=y^{3n}_{11}$, then we can substitute
to find a solution.
\end{answer}
To match nested things, you probably want to use Regexp::Common, which
allows you to do that very easily:
use Regexp::Common;
$text =~ s
\\ backans {
( $RE{balanced}{-parens='{}'} )
}
\\begin{answer}\n$1\n\\end{answer}xg;
The /x modifier is so that I can have extra whitespace, and the /g
modifier means do it globally. The %RE hash is quite magical -- see the
Regexp::Common docs for an explanation. The module isn't standard,
though, so you'd have to download it from CPAN yourself.
If you want a stand-alone solution, you can have one if you make use of
some of Perl's special regex constructs:
my $rx; # must be declared first...
$rx = qr[
(?:
(? [^{}\\]+ | \\. )
|
{ (??{ $rx }) }
)*
]xs;
$text =~ s/\\backans{($rx)}/\\begin{answer}\n$1\n\\end{answer}/g;
Its primary trick is the (??{ ... }) assertion, which evaluates its
contents as PART of the regex to match. Since its contents are $rx
itself, it basically creates an automatically deeply-enough nested regex
for you on the fly.
--
Jeff japhy Pinyan [EMAIL PROTECTED] http://www.pobox.com/~japhy/
RPI Acacia brother #734 http://www.perlmonks.org/ http://www.cpan.org/
CPAN ID: PINYAN[Need a programmer? If you like my work, let me know.]
stu what does y/// stand for? tenderpuss why, yansliterate of course.
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Re: nested foreach not looping properly
Mike Re-V wrote:
The following code iterates unexpectedly. I want to loop thru the
file 'file.dat' and pull out every field that begins with 650. The
code then pulls the 650 field and builds an array from the
sub-fields. The code works but I'm stuck on the first record. In
other words if the file I'm reading has 2000 records I get the
first 650 record 2000X
use MARC::Batch;
my $batch =MARC::Batch-new('USMARC','file.dat');
my $record = $batch-next();
## get all the 852 fields (list context).
my @fields = $record-field('852');
## examine each 852 field and print it out.
while (my $record = $batch-next())
{
foreach my $field (@fields) {
print $field-as_string(),\n;
}
}
I don't know anything about the MARC::Batch module, but I notice that
the foreach loop is running independently from variables set in the
while() loop. Consequently, it does not surprise me when you say that
you are stuck.
Btw, why don't you enable strictures and warnings?
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Re: nested parens
Let's test it.
use strict;
use warnings;
use Data::Dumper 'Dumper';
foreach my $string (
'(foo) (bar)',
'(foo) (bar) (baz)',
'((foo) bar)) (baz)',
'(foo bar)',) {
my @text_inside_parens = $string =~ m/\((.*)\)/g;
print Dumper [EMAIL PROTECTED];
}
__END__
I get:
$VAR1 = [
'foo) (bar'
];
$VAR1 = [
'foo) (bar) (baz'
];
$VAR1 = [
'(foo) bar)) (baz'
];
$VAR1 = [
'foo bar'
];
.* is greedy. I suspect @text_inside_parens will
never have more than one element in it.
Right, The point was, regexes could help, I never said it wasn't greedy
or the example was 100% what he needed, just a suggestion for another
place to start looking :)
(I figured it was a *little* better than `perldoc perlre` ;p)
Thanks for taking the time to do that example.
Lee.M - JupiterHost.Net
HTH,
Charles K. Clarkson
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Re: nested parens
Charles K. Clarkson wrote:
JupiterHost.Net [EMAIL PROTECTED] wrote:
:
: [EMAIL PROTECTED] wrote:
: Is there a module out there that I can use to parse
: a text line and return the pieces that are enclosed
: in paren's?
:
: You don't need a module for that just use regex's:
:
: my @text_inside_parens = $string =~ m/\((.*)\)/g;
Let's test it.
use strict;
use warnings;
use Data::Dumper 'Dumper';
foreach my $string (
'(foo) (bar)',
'(foo) (bar) (baz)',
'((foo) bar)) (baz)',
'(foo bar)',) {
my @text_inside_parens = $string =~ m/\((.*)\)/g;
print Dumper [EMAIL PROTECTED];
}
__END__
I get:
$VAR1 = [
'foo) (bar'
I see. Someone dun fergot the lazy symbol, huh?
...
.* is greedy. I suspect @text_inside_parens will
never have more than one element in it.
good point.
...
my @text_inside_parens = $string =~ m/\((.*?)\)/g;
print Dumper [EMAIL PROTECTED];
}
__END__
$VAR1 = [
'foo',
'bar'
];
$VAR1 = [
'foo',
'bar',
'baz'
];
...
Joseph
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Re: nested parens
Let's test it.
use strict;
use warnings;
use Data::Dumper 'Dumper';
foreach my $string (
'(foo) (bar)',
'(foo) (bar) (baz)',
'((foo) bar)) (baz)',
'(foo bar)',) {
my @text_inside_parens = $string =~ m/\((.*)\)/g;
print Dumper [EMAIL PROTECTED];
}
__END__
I get:
$VAR1 = [
'foo) (bar'
];
$VAR1 = [
'foo) (bar) (baz'
];
$VAR1 = [
'(foo) bar)) (baz'
];
$VAR1 = [
'foo bar'
];
.* is greedy. I suspect @text_inside_parens will
never have more than one element in it.
Right, The point was, regexes could help, I never said it wasn't greedy
or the example was 100% what he needed, just a suggestion for another
place to start looking :)
(I figured it was a *little* better than `perldoc perlre` ;p)
To illustrate further try:
perl -e 'my $str = (hi)((bye)j(hi))(sweet);my @m = $str =~
m/\(([^(^).]*)\)/g; for(@m) { print -$_-\n; }'
See? No module, lots of regex :) Again, maybe not exactly what they
needed (IE It misses the middle 'j')but an illustration of an idea.
And so everyone who is playing along at home:
#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper 'Dumper';
foreach my $string (
'(foo) (bar)',
'(foo) (bar) (baz)',
'((foo) bar)) (baz)',
'(foo bar)',) {
my @text_inside_parens = $string =~ m/\(([^(^).]*)\)/g;
print Dumper [EMAIL PROTECTED];
}
HTH
Lee.M - JupiterHost.Net
Thanks for taking the time to do that example.
Lee.M - JupiterHost.Net
HTH,
Charles K. Clarkson
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Re: nested parens
[EMAIL PROTECTED] wrote: Is there a module out there that I can use to parse a text line and return the pieces that are enclosed in paren's? You don't need a module for that just use regex's: my @text_inside_parens = $string =~ m/\((.*)\)/g; HTH Lee.M - JupiterHost.Net Thanks -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
RE: nested parens
JupiterHost.Net [EMAIL PROTECTED] wrote:
:
: [EMAIL PROTECTED] wrote:
: Is there a module out there that I can use to parse
: a text line and return the pieces that are enclosed
: in paren's?
:
: You don't need a module for that just use regex's:
:
: my @text_inside_parens = $string =~ m/\((.*)\)/g;
Let's test it.
use strict;
use warnings;
use Data::Dumper 'Dumper';
foreach my $string (
'(foo) (bar)',
'(foo) (bar) (baz)',
'((foo) bar)) (baz)',
'(foo bar)',) {
my @text_inside_parens = $string =~ m/\((.*)\)/g;
print Dumper [EMAIL PROTECTED];
}
__END__
I get:
$VAR1 = [
'foo) (bar'
];
$VAR1 = [
'foo) (bar) (baz'
];
$VAR1 = [
'(foo) bar)) (baz'
];
$VAR1 = [
'foo bar'
];
.* is greedy. I suspect @text_inside_parens will
never have more than one element in it.
HTH,
Charles K. Clarkson
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Re: nested parens
[EMAIL PROTECTED] wrote: Is there a module out there that I can use to parse a text line and return the pieces that are enclosed in paren's? Yep, a core module name Text::Balanced. Randy. -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
RE: nested parens
thanks -Original Message- From: Randy W. Sims [mailto:[EMAIL PROTECTED] Sent: Friday, April 02, 2004 5:24 PM To: ewalker Cc: [EMAIL PROTECTED] Subject: Re: nested parens [EMAIL PROTECTED] wrote: Is there a module out there that I can use to parse a text line and return the pieces that are enclosed in paren's? Yep, a core module name Text::Balanced. Randy. thanks -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
RE: nested while loops using DBI
On Mon, 2004-03-22 at 18:04, Guay Jean-Sbastien wrote:
Hello Mike,
$row=$dbh-prepare(SELECT contact_id,first_name,last_name,organisation
FROM tb_contacts WHERE organisation ILIKE ?);
[...]
while(($id,$first_name,$last_name,$organisation) = $row-fetchrow_array())
{
[...]
$row=$dbh-prepare(SELECT id,contact_id,type_of_contact,priority FROM
tb_contact_role WHERE contact_id ILIKE ?);
[...]
}
[...]
This only produces on record at the top-level, if I dont have the select
inside the loop, then all matching records appear
Anyone any idea where I am going wrong
You are using the same variable as the statement handle for both queries
($row). In effect, since your second SELECT probably returns only one row
(probably the detail of the contact you got in the first SELECT), the
enclosing while ends afterwards because there are no more rows to get from
that statement handle (the second SELECT).
Yeah I worked this out just after I posted.
I would suggest you declare a new variable inside your while, say $contact.
Something like this:
my $contact = $dbh-prepare(qq[SELECT id, contact_id, type_of_contact,
priority
FROM tb_contact_role
WHERE contact_id ILIKE ?]);
I also suggest better indentation and whitespace usage in your code. That
will get very hard to read very fast...
Hope that helps,
J-S
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RE: nested while loops using DBI
Hello Mike,
$row=$dbh-prepare(SELECT contact_id,first_name,last_name,organisation
FROM tb_contacts WHERE organisation ILIKE ?);
[...]
while(($id,$first_name,$last_name,$organisation) = $row-fetchrow_array())
{
[...]
$row=$dbh-prepare(SELECT id,contact_id,type_of_contact,priority FROM
tb_contact_role WHERE contact_id ILIKE ?);
[...]
}
[...]
This only produces on record at the top-level, if I dont have the select
inside the loop, then all matching records appear
Anyone any idea where I am going wrong
You are using the same variable as the statement handle for both queries
($row). In effect, since your second SELECT probably returns only one row
(probably the detail of the contact you got in the first SELECT), the
enclosing while ends afterwards because there are no more rows to get from
that statement handle (the second SELECT).
I would suggest you declare a new variable inside your while, say $contact.
Something like this:
my $contact = $dbh-prepare(qq[SELECT id, contact_id, type_of_contact,
priority
FROM tb_contact_role
WHERE contact_id ILIKE ?]);
I also suggest better indentation and whitespace usage in your code. That
will get very hard to read very fast...
Hope that helps,
J-S
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Re: nested Paren's
Eric Walker wrote:
Hey all,
I have a file with some data that has like nested parens.. example
yes( hello goodbye
( (one 2) (two 3) (three 4)
)
(( mon 1) (tues 2) (wed 3)
)
((jan 1) (feb 2) (march 3)
)
)
I need help in trying to break this up and make key value pairs out of
the data example:
KEYVALUE
one 2
two 3
three4
mon 1
tues 2
wed 3
jan 1
feb 2
march 3
there are many ways of doing that, here is one:
#!/usr/bin/perl -w
use strict;
(my $parens=PARENS) =~ s/\n//g;
(one 2) (two 3) (three 4)
)
((mon 1) (tues 2) (wed 3)
)
((jan 1) (feb 2) (march 3)
)
PARENS
my %hash = map split, $parens =~ /\(+([^()]+)\)+/g;
while(my($name,$value) = each %hash){
print $name,$value\n;
}
__END__
prints:
feb,2
jan,1
three,4
march,3
one,2
mon,1
wed,3
tues,2
two,3
depends on the actual data you have, you might need to modify the above
slightly to suit your case. another way of doing it is to remove the parens
and replace multiple spaces with one and then split on a single space to
get the name value pair you want but this approach is slightly less
efficient than the proposed one. it's, however, a bit easier to code.
david
--
s,.*,,e,y,\n,,d,y,.s,10,,s
.ss.s.s...s.sss.s.ss
s.s.s...s...s..s
...s.ss..s.sss..ss.sss.s
s.s.s...ss.sss.s
..s..sss.s.ss.sss...
..ssss.sss.sss.s
,{4},|?{*=}_'y!'+0!$;
,ge,y,!#:$_(-*[./[EMAIL PROTECTED],b-t,
.y...,$~=q~=?,;^_#+?{~,,$~=~
y.!-*-/:[EMAIL PROTECTED] ().;s,;,
);,g,s,s,$~s,g,y,y,%,,g,eval
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Re: nested Paren's
On Dec 11, 2003, at 9:30 AM, Eric Walker wrote:
[..]
yes( hello goodbye
( (one 2) (two 3) (three 4)
)
(( mon 1) (tues 2) (wed 3)
)
((jan 1) (feb 2) (march 3)
)
)
[..]
The question of course is whether that 'ordering'
is important, or can you just use a hash?
IF you do not really need to know about the
paren count then don't count it. IF you
know that your generalized date is going to
be of the form
(word num)
then your word_num regEx would look like
my $word_num = qr/\( # our opening paren
(\w+)\s+(\d+)
\)/ix; # our closing paren
I use the 'x' option to lay it out pretty like that.
then the rest is a walker
while ( INFO1 ) {
chomp;
next if (/^\s*$/); # no need empty lines
s/^\s+//; # kill leaing lines
my $line = $_; # now we have a line to play with
while ( $line =~ /$word_num(.*)/)
{
$hash{$1} = $2; # our $word_num pattern fetched these
$line = $3; # for everything else there is (.*)
}
}
while (my ($k, $v) = each %hash)
{
print $k - $v\n;
}
ciao
drieux
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Re: nested Paren's
Well, the problem is that this is just one section of a file the other
sections actualy have different format. When I get to this section I key
on the section name to know how to process it and will need to key on
the last paren know that this section is done and to try and key on what
the next section is and how it is processed. Not all of the data in
this section is of the form mon 1 every know and then you get something
like list( one two). The data i am making up as I didn't think it
was important. I figured the form is what was needed. Once I get the
key value pairs it doesn't matter because I am going to read another
file like this and compare the data to make sure nothing has changed
between the two files. I like the regx thing tho, it gives me some
ideas.. I will see if I can make it work with that...
perl knucklehead
On Thu, 2003-12-11 at 11:28, drieux wrote:
On Dec 11, 2003, at 9:30 AM, Eric Walker wrote:
[..]
yes( hello goodbye
( (one 2) (two 3) (three 4)
)
(( mon 1) (tues 2) (wed 3)
)
((jan 1) (feb 2) (march 3)
)
)
[..]
The question of course is whether that 'ordering'
is important, or can you just use a hash?
IF you do not really need to know about the
paren count then don't count it. IF you
know that your generalized date is going to
be of the form
(word num)
then your word_num regEx would look like
my $word_num = qr/\( # our opening paren
(\w+)\s+(\d+)
\)/ix; # our closing paren
I use the 'x' option to lay it out pretty like that.
then the rest is a walker
while ( INFO1 ) {
chomp;
next if (/^\s*$/); # no need empty lines
s/^\s+//; # kill leaing lines
my $line = $_; # now we have a line to play with
while ( $line =~ /$word_num(.*)/)
{
$hash{$1} = $2; # our $word_num pattern fetched these
$line = $3; # for everything else there is (.*)
}
}
while (my ($k, $v) = each %hash)
{
print $k - $v\n;
}
ciao
drieux
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Re: nested Paren's
Ok,, back to some laymen terms hehe... The file is read by an application and what I am doing is this. The application use to read this file that was created by hand to set some internal settings. I a wrote a program to pull the same info from a database. The auto generated file will ultimately be use for the program to read and set these internal values. I am trying to dump the current values from the program and do a compare between the file I auto created and whats in the program now. this is why I am trying to suck in all the values so I can do a compare and make sure the auto generated file does the same things as the current file that was made by hand. So the keys Idea is a no go. I am glad at least the data was good enough for us to kick around. The way they are writting is the only way they can be do to the application that reads them. How do you determine if an application has a portable library? I know nothing of that but sounds like something neat and witty.. If I could do that and use a perl module that would be nice. perlknucklehead I know nothing of xml I am sorry to say. you kinda dove off of the big diving board and I am still back putting on my floaters. hehehe... On Thu, 2003-12-11 at 12:39, drieux wrote: On Dec 11, 2003, at 10:52 AM, Eric Walker wrote: Well, the problem is that this is just one section of a file the other sections actualy have different format. [..] every know and then you get something like list( one two). [..] The data i am making up as I didn't think it was important. I figured the form is what was needed. [..] Once I get the key value pairs it doesn't matter because I am going to read another file like this and compare the data to make sure nothing has changed between the two files. [..] p0: the 'data' that you made up, was good enough to get us some direction to start looking at solutions. p1: You might ultimately want to look at a re-write of how those 'files' are being created, so that the sub-sequent post parsing is simpler. IF that is not an option - then you might want to see if the application that created the format has a library that can be 'ported' and hence build out a perl module of your own that would share it's parser structure. p1.1 - either go with say an xml-ish model hence use the LibXml module for parsing p1.2 - assume that the applications library is lib_fung_parser.so - then you want to get your hands on the header files and use h2xs to generate your Fung::Parser module p2: The problem of multiple section readings from a file should lead you towards a simpler process where you have keys in the file that indicate which 'parser' to be using at which point you might want to look at a 'dispatcher'... where each 'function' knows how\ to return stuff related to what it knows how to read, and specifically how it's 'end of section' will tell it to stop parsing and go back. ciao drieux --- -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
Re: nested Paren's
On Dec 11, 2003, at 12:16 PM, Eric Walker wrote:
Ok,, back to some laymen terms hehe...
not sure I can do that, but hey, I'll try anything once...
it seems that the two issues are
a. Parser Mechanics
b. File Format.
The file is read by an application and what I am doing is this.
The application use to read this file that was created by hand
to set some internal settings.
The first question is who wrote the application,
and, well, to be polite, did the application writer
share the parser code the it is using to read the file.
But we will get back to this...
for the sake of argument let's assume the simpler
myApp -f config_file
and myApp parses the config_file and set's it's internal values.
{ yes, the myApp could be reading some 'default config file',
'user preferance files', what ever - there exists some file
let us call it the 'config_file' that will be read to configure
the application . }
[..]
I am trying to dump the current values from the program
and do a compare between the file I auto created
and whats in the program now.
There exists some 'signal' or 'messaging' method that
will tell myapp:
woof your current configuration data into a file
{ woof - technical term denoting, to heave up the foo.. }
[..]
So the keys Idea is a no go. I am glad at least the data was good
enough for us
to kick around. The way they are writting is the only way they can be
do to the application that reads them.
Actually what you will want to step into is
the notion of 'subs' - cf perldoc perlsub,
and you can 'abstract' the 'grovel_woof_file()'
so that it will return you a hash.
eg:
suf grovel_woof_file
{
my ($filename) = @_;
# return undefined if we can not read the file.
return undef unless (-r $filename );
# steal from dzhuo[at]looksmart.net (David)
open(FD, $filename) or die unable to open $filename :$!;
my $parens;
$parens .= $_ while(FD); # read in the file
close(FD);
# cf perdoc map - and thank david.
my %hash = map split, $parens =~ /\(+([^()]+)\)+/g;
\%hash; # return hash ref
}
{ Yes, I know, that will ultimately need to be grown out
a bit to deal with the 'variations' in the 'configuration file'
as noted previously... }
then you could do say
my $def_hash = grovel_woof_file($default_file);
make_myApp_woof($new_file); # function to make running myApp Woof...
my $new_hash = grovel_woof_file($new_file);
foreach my $key ( keys %$def_hash )
{
if ( exists($new_hash-{$key}))
{
if ( $new_hash-{$key} eq $def_hash-{$key}) {
print have same key $key\n;
} else {
whine(new key value, $key, $new_hash-{$key});
}
} else {
whine(no key value, $key, $def_hash-{$key});
}
}
we leave the whine() function to you as an exercise to whine about.
{ we will serve no whine() before it's time... }
How do you determine if an application has a portable library?
well it is less about being 'portable' in terms of being
able to run on more than one os - as much as it is about
exposing the parser complex that the application is using.
WARNING: drieuxishSoapBoxMoment
drieuxishSoapBoxMoment
Files do not Just GROW in File Systems! There
exists some 'code foo' that creates it, normally
because there is some 'parser foo' that will read it
into applications to set configuration information.
Writers of Configuration File Parsers SHOULD be polite
and offer up access to their Configuration File Parsing
routines so that they can be exposed in other languages,
such as Perl, so that the support crew can be more effective!
App Writers who create WACKO configuration file stuff so as
to create Wacko Configuration File Parsers that they are not
willing to share with their support crew are building up bad
kharma, and the BadKharmaFerrie Will Get them at PayBack!
/drieuxishSoapBoxMoment
{ I feel better now. }
I know nothing of that but sounds like something neat and witty..
If I could do that and use a perl module
that would be nice.
what you will want to learn down that path is
perldoc h2xs
perldoc perlmodlib
and specifically you will want to pick up
learning Perl Objects, References and Modules,
as well as the 3rd Edition of Programming perl...
perlknucklehead
I know nothing of xml I am sorry to say. you kinda dove off of the big
diving board and I am still back putting on my floaters. hehehe...
sorry, that Must have been my evil twin Skippy
ciao
drieux
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Re: Nested quantifiers error?
On Oct 17, Michael Weber said:
When I try to find out what the spam score is I am getting a weird error.
It's not that weird an error. Perl is telling you exactly what's wrong,
exactly where it's wrong.
if ( $msg[$line] =~ '^X-Spam-Level: ***' ) {
$bad_spam += 1;
}
Nested quantifiers before HERE mark in regex m/^X-Spam-Level: ** HERE
*/ at /home/filter/grab.pl line 16.
Why am I getting a HERE marker? Do I need to escape all the *s? Do I
need to do something else?
The HERE is telling you where in the regex the problem is. The
problem is that '*' is a regex metacharacter. Just because your regex is
in single quotes (not a smart idea, because it's misleading) doesn't mean
that it's NOT a regex.
$bad_spam++ if $msg[$line] =~ /^X-Spam-Level: \*{11}/;
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stu what does y/// stand for? tenderpuss why, yansliterate of course.
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Re: nested anonymous reference syntax
[EMAIL PROTECTED] wrote:
Hello,
I'm having trouble grasping the syntax to perform foreach operation on an
anonymous array within an anonymous hash reference.
my $hashRef = { bah = humbug,
list = [ lions, tigers, bears, oh_my ],
woo = hoo };
here you have a hash ref named $hashRef
How can I run a foreach on every item in that anonymous array reference
that
is a value of the key list in the hash reference? I'm having great
difficulties getting this to work. Is it even possible without nested
foreach
structures? I would think it would be something like:
foreach my $listItem (@{$hashref{list}}) {
print $_list item is one item of the array! Woo hoo!\n;
}
here you are trying to access the 'list' slot of a hash named $hashref which
on course is different than $hashRef you declared above. not to mention
that you are not treating $hashref as hash reference, you are using it as a
hash. which one is it? is $hashref really a hash reference or just a hash?
is $hashRef the same as $hashref?
if $hashref is the same as $hashRef and it's really a hash reference, try:
for(@{$hashRef-{list}}){
print $_\n;
}
if $hashref is NOT the same as $hashRef and it's really just a hash, you
have the right syntax:
for(@{$hashref{list}}){
print $_\n;
}
david
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Re: nested anonymous reference syntax
[EMAIL PROTECTED] wrote:
I'm having trouble grasping the syntax to perform foreach operation on an
anonymous array within an anonymous hash reference.
my $hashRef = { bah = humbug,
list = [ lions, tigers, bears, oh_my ],
woo = hoo };
How can I run a foreach on every item in that anonymous array reference that
is a value of the key list in the hash reference? I'm having great
difficulties getting this to work. Is it even possible without nested foreach
structures? I would think it would be something like:
foreach my $listItem (@{$hashref{list}}) {
print $_list item is one item of the array! Woo hoo!\n;
}
But, that does not work.
I know this works:
foreach my $item (${$hashRef}{list}) {
foreach (@$item) {
print $_\n;
}
}
But, that seems like a lot of unnecessary work, iteration, and typing. I
would appreciate any help. Thanks in advance! :)
Hi Chris.
Very nearly right, but its
foreach my $listItem (@{$hashref{list}}) {
print $listItem is one item of the array! Woo hoo!\n;
}
OR
foreach (@{$hashref{list}}) {
print $_ is one item of the array! Woo hoo!\n;
}
HTH,
Rob
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Re: nested parenthesis in regex and launching a new process
On Tuesday, September 2, 2003, at 11:51 PM, Bryan Harris wrote: Thanks for the info, James. Sounds like threading is still a ways over my head, but forking sounds interesting. I have a perl script that does simple find-replaces within all the files passed to it (the key parts were written by very kind people on this list, actually). Would it be advantageous for the script to fork so that it could be find-replacing on all files simultaneously as opposed to serially? I seriously doubt it. It's usually a bad idea to make anything more complicated than strictly needed. Multiprocessing is a lot of work, mostly because you have to control how information is shared between the two processes/threads. For example, even in a simple find and replace script, each part would have to know which files were being handled by the other processes/threads. Save forking and threading for when you absolutely must do two or more things at once, say in servers, complex GUIs, etc. Hope that helps. James -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: nested parenthesis in regex and launching a new process
I seriously doubt it. It's usually a bad idea to make anything more complicated than strictly needed. Multiprocessing is a lot of work, mostly because you have to control how information is shared between the two processes/threads. For example, even in a simple find and replace script, each part would have to know which files were being handled by the other processes/threads. Save forking and threading for when you absolutely must do two or more things at once, say in servers, complex GUIs, etc. Thanks, James. - Bryan -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: nested parenthesis in regex and launching a new process
ZSDC,
I love this stuff! You explain these concepts very clearly, have you ever
considered teaching? I'm happy to keep asking questions as long as you're
willing to answer them. =)
Servers often work this way. There's a process listening on a port but
when someone connects, it doesn't serve the actual request (which would
block the server and no one else could connect until it's done) but only
forks the child, which then serves the request, and the parent keeps
listening for another requests and forks another children at the same time.
Neat! Is this how threads are spawned? or are forked processes different
from threads?
If this is how threads are spawned, how do big commercial apps manage to do
multiple things at once without completely duplicating the entire executable
in RAM? or is Perl's implementation less robust than the one used for
C++-type apps?
As for the client side, you could for example have a mail client
downloading mail in the background, while the user can keep writing and
sending mail at the same time, etc. Check out this example:
#!/usr/bin/perl -w
open F, '+', $0-result or die $!;
What is '+'? I've never seen that before.
defined(my $pid = fork) or die $!;
unless ($pid) {
# child:
sleep 5; # an important time consuming task...
print F 123\n;
exit;
}
# parent:
print Not yet... Do something else.\n and sleep 1 until -s F;
I haven't seen the '-s F' notation either -- is it a -x file test?
Yes. Actually, there's a whole genealogy tree. The process with ID 1
(usually called init) is the protoplast of every other process running
on the system. This is the only process without a parent.
The killing of children makes sense when e.g. I open an xterm window and
run man fork. What I have now is a shell process which is a child of
xterm, a man process which is a child of the shell and a pager (for
scrolling man's output) which is a child of man. Now, when I just close
the xterm window, the pager, man and shell are killed as well. It makes
sense, because keeping them running (sleeping, actually) would be pointless.
This is all starting to make sense now... Thank you!
But sometimes you don't want that. For example, your ssh connection
could die, everything is killed and you have to connect and login once
again and start everything from the beginning. If you don't want that,
then check out this great little program:
Once you background a run in a shell, though, it seems to keep running, at
least on our SGIs. How does that work? For example, I set a complex model
running with:
% itods myfile.txt
Now if I exit the shell, the process keeps going. How does that fit in?
What is a session? I've never heard of that...
A session is basically (it's an oversimplification) a bunch of processes
which get killed if you close the session, because they are important
only for that session (like the example with xterm). For more
informations see:
man setsid
http://linux.ctyme.com/man/man2993.htm
man getsid
http://linux.ctyme.com/man/man0960.htm
man setpgid
http://linux.ctyme.com/man/man2984.htm
Nice!
I'm glad I could be helpful. This subject usually causes lots of
confusion. I hope others could also find it interesting and didn't mind
if I was a little bit off topic.
Thanks again.
- Bryan
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Re: nested parenthesis in regex and launching a new process
On Friday, August 29, 2003, at 01:32 AM, Bryan Harris wrote: Neat! Is this how threads are spawned? or are forked processes different from threads? If this is how threads are spawned, how do big commercial apps manage to do multiple things at once without completely duplicating the entire executable in RAM? or is Perl's implementation less robust than the one used for C++-type apps? Forking a process and threads are two different things actually. Forking makes a copy of the running process. From there, the parent and child processes can do separate things. Threading is using different streams of execution. There's only one process there, but it's doing multiple things internally. Really, they're two different ways to solve the same problem. Traditionally, forking was the UNIX way to handle this, while a lot of other platforms preferred threading. Today, you usually have both options available to you in most cases. (Windows doesn't generally support forking, but Perl on Windows does with heavy magic.) Personally, I find forking a little easier to setup and follow. As you noted though, copying the entire process is a less than ideal use of resources, so threading is generally a little more robust, for most things. Going back to servers as an example, forking works out pretty well for a web server that just needs to hand incoming requests the page they asked for (oversimplified a little). However, forking a chat server would generally be a bad idea, in my opinion. Once you had 50 users talking to each other, you would have 50 copies of all the state information the server tracks. Threading would server better here. (Technically, you can do both of the above with Non-Blocking I/O as well, eliminating the need to fork or thread. That's significantly harder though and off topic for this discussion.) As a final detail, you will probably need to compile your own version of Perl if you want to use its threading options. Hope that clears some things up. James -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: nested parenthesis in regex and launching a new process
Thanks for the info, James. Sounds like threading is still a ways over my head, but forking sounds interesting. I have a perl script that does simple find-replaces within all the files passed to it (the key parts were written by very kind people on this list, actually). Would it be advantageous for the script to fork so that it could be find-replacing on all files simultaneously as opposed to serially? Thanks again... - Bryan -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: nested parenthesis in regex and launching a new process
The fork concept can be quite confusing at first, but it is actually
quite simple, once you get used to it. Check out the output of this
little program:
[ very interesting stuff cut out ]
Wild! Why would anyone ever use this? Why would you ever want to clone
yourself at the current point and have both continue on running? I guess I
could see it being a smooth way to process a hundred files all at once
(sort-of)... I don't get it.
[ more interesting stuff cut out ]
with '' your program won't wait for the other-program to finish, but
the other-program process will die when your program (the parent
process) finishes.
Why is this? Does that mean if I create a new tcsh shell, run an app, kill
the tcsh shell before the app finishes, that the app will die too? Why have
parent/child relationships in processes? Are there such things as
grandchildren/grandparents?
Of course you want your program to finish without killing the child
processes in the process (pun definitely intended) and for that you need
your child processes to create new sessions with setsid().
What is a session? I've never heard of that...
You can take a look at Proc::Daemon module on CPAN, but it's not exactly
what you need, mostly because it redirects STDOUT to /dev/null, while
you want your processes to write to STDOUT (by the way, are you sure
about that? it can result in a total mess printed on your terminal) but
still you may want to read its source to see how it works:
http://search.cpan.org/src/EHOOD/Proc-Daemon-0.03/Daemon.pm
Yes, I absolutely want all output going to STDOUT. Thanks for foreseeing a
potential problem, though...
use POSIX 'setsid';
sub forkrun ($) {
my $cmd = pop;
defined(my $pid = fork) or die $0: fork: $!\n;
unless ($pid) {
setsid or die $0: setsid: $!\n;
exec $cmd;
}
return $pid;
}
Yes! This works terrifically!
How does the fork part work within subroutines? I'm guessing the part
starting with unless looks to see if it's now a child process, and if so,
to quit the current perl script and start off $cmd. Is that right?
It works, so that part's taken care of. Now I just have to figure out how
it works. =) Thanks a lot zsdc.
- Bryan
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Re: nested parenthesis in regex and launching a new process
Bryan Harris wrote:
The fork concept can be quite confusing at first, but it is actually
quite simple, once you get used to it. Check out the output of this
little program:
[ very interesting stuff cut out ]
Wild! Why would anyone ever use this? Why would you ever want to clone
yourself at the current point and have both continue on running? I guess I
could see it being a smooth way to process a hundred files all at once
(sort-of)... I don't get it.
Servers often work this way. There's a process listening on a port but
when someone connects, it doesn't serve the actual request (which would
block the server and no one else could connect until it's done) but only
forks the child, which then serves the request, and the parent keeps
listening for another requests and forks another children at the same time.
As for the client side, you could for example have a mail client
downloading mail in the background, while the user can keep writing and
sending mail at the same time, etc. Check out this example:
#!/usr/bin/perl -w
open F, '+', $0-result or die $!;
defined(my $pid = fork) or die $!;
unless ($pid) {
# child:
sleep 5; # an important time consuming task...
print F 123\n;
exit;
}
# parent:
print Not yet... Do something else.\n and sleep 1 until -s F;
seek F, 0, 0;
print Done! The result is , F;
It could be written better with pipes, or real temp files, but it's
cleaner that way. The child could do something more interesting than
sleeping, like downloading a webpage from a slow server, without totally
freezing our program. The parent might decide to wait only ten seconds
and then give up, or try again downloading from another mirror, etc.
Instead of one process, you can have few processes running
simultaneously and interacting with each other, while every one of them
is a different incarnation of the same program. It can be very powerful.
[ more interesting stuff cut out ]
with '' your program won't wait for the other-program to finish, but
the other-program process will die when your program (the parent
process) finishes.
Why is this? Does that mean if I create a new tcsh shell, run an app, kill
the tcsh shell before the app finishes, that the app will die too? Why have
parent/child relationships in processes? Are there such things as
grandchildren/grandparents?
Yes. Actually, there's a whole genealogy tree. The process with ID 1
(usually called init) is the protoplast of every other process running
on the system. This is the only process without a parent.
The killing of children makes sense when e.g. I open an xterm window and
run man fork. What I have now is a shell process which is a child of
xterm, a man process which is a child of the shell and a pager (for
scrolling man's output) which is a child of man. Now, when I just close
the xterm window, the pager, man and shell are killed as well. It makes
sense, because keeping them running (sleeping, actually) would be pointless.
But sometimes you don't want that. For example, your ssh connection
could die, everything is killed and you have to connect and login once
again and start everything from the beginning. If you don't want that,
then check out this great little program:
http://www.gnu.org/software/screen/
It's truely amazing.
Of course you want your program to finish without killing the child
processes in the process (pun definitely intended) and for that you need
your child processes to create new sessions with setsid().
What is a session? I've never heard of that...
A session is basically (it's an oversimplification) a bunch of processes
which get killed if you close the session, because they are important
only for that session (like the example with xterm). For more
informations see:
man setsid
http://linux.ctyme.com/man/man2993.htm
man getsid
http://linux.ctyme.com/man/man0960.htm
man setpgid
http://linux.ctyme.com/man/man2984.htm
You can take a look at Proc::Daemon module on CPAN, but it's not exactly
what you need, mostly because it redirects STDOUT to /dev/null, while
you want your processes to write to STDOUT (by the way, are you sure
about that? it can result in a total mess printed on your terminal) but
still you may want to read its source to see how it works:
http://search.cpan.org/src/EHOOD/Proc-Daemon-0.03/Daemon.pm
Yes, I absolutely want all output going to STDOUT. Thanks for foreseeing a
potential problem, though...
Instead of /dev/null you could also redirect STDOUT to real files (or
pipes or sockets or whatever), so you could capture and access it
without all the mess on your screen.
use POSIX 'setsid';
sub forkrun ($) {
my $cmd = pop;
defined(my $pid = fork) or die $0: fork: $!\n;
unless ($pid) {
setsid or die $0: setsid: $!\n;
exec $cmd;
}
return $pid;
}
Yes! This works terrifically!
Great.
How does the fork part work within subroutines? I'm guessing the part
starting with unless looks to
Re: nested parenthesis in regex and launching a new process
Bryan Harris wrote: ... which seems to work (correctly returns file_3.1.1), but I'm not sure how the nested parenthesis are supposed to be referenced. How would I get what was matched by the inner set? Is this the best way to do this? Everything is captured in $1, $2, $3... in the order of opening parenthesis, from left to right. 2. How do I set off a new process, not waiting or caring about any return values? $myApp = /proj/mycoolexecutable; $myOptions = -f -n2 file1 file2; # execute $myApp. .$myOptions here, and do not wait for any return values See: perldoc -f fork perldoc -f exec -zsdc. -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: nested parenthesis in regex and launching a new process
2. How do I set off a new process, not waiting or caring about any return values? $myApp = /proj/mycoolexecutable; $myOptions = -f -n2 file1 file2; # execute $myApp. .$myOptions here, and do not wait for any return values See: perldoc -f fork perldoc -f exec Thanks for replying zsdc. The $1,$2 thing makes perfect sense now. As for the fork/exec thing, those pages are a little over my head. I don't understandhow process signals and pipes work. Really, all I want the perl script to do is the equivalent of typing $myApp. .$myOptions at the command line, sending its output to STDOUT. This script readsin all input files passed to it, determines which executable applies to each, andlaunches that executable with that file as a parameter. It may need to launch 5 or 6processes, but I want it to gracefully exit when it's done launching and not wait tillthose processes finish. Does that make sense? Is that even possible? Thanks again. - Bryan -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: nested pattern match
Rob and David,
Thanks very much! That's exactly what I am looking
for and sorry for the misleading subject on the email.
Rob: Could you please explain why you need 2 questions
marks on line#7 instead of just one minimal quantifier
needed (I hope I am using the right words this time
!!!).
Thanks,
Ramesh
1 while ( $code =~ m{
2\#(ifn?def) \s+ def \s* \n
3(.*?) \s+
4(?:
5\#else \s+ def \s* \n
6(.*?) \s+
7)??
8\#endif \s+ def \s* \n
9 }isxg ) {
10 my ($def, $undef) = $1 eq 'ifdef' ? ($2, $3
11 || '') : ($3 || '', $2);
12 printf Defined: %s\n, $def;
13 printf Undefined: %s\n, $undef;
14 print \n;
}
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Re: nested pattern match
Raghupathy [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED]
Rob and David,
Thanks very much! That's exactly what I am looking
for and sorry for the misleading subject on the email.
Rob: Could you please explain why you need 2 questions
marks on line#7 instead of just one minimal quantifier
needed (I hope I am using the right words this time
!!!).
Thanks,
Ramesh
1 while ( $code =~ m{
2\#(ifn?def) \s+ def \s* \n
3(.*?) \s+
4(?:
5\#else \s+ def \s* \n
6(.*?) \s+
7)??
8\#endif \s+ def \s* \n
9 }isxg ) {
10 my ($def, $undef) = $1 eq 'ifdef' ? ($2, $3
11 || '') : ($3 || '', $2);
12 printf Defined: %s\n, $def;
13 printf Undefined: %s\n, $undef;
14 print \n;
}
Sure. The first question mark is a quantifier: the same as
{0,1}, meaning 'match one repetition if possible, otherwise
none'. The second is a non-greedy modifier, turning it into
'match no repetitions if possible, otherwise one'.
HTH,
Rob
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Re: nested pattern match
Raghupathy wrote: Hi All, I have a text file as shown below. How do I match patterns like the following: Pattern to be matched: = #ifndef def .. (anything except #if) #else def ... (anything except #if) #endif def My Input Data: = #ifndef def DELETE sys1..tbl1 #endif def SELECT col1, col2, col3 #ifndef def FROMsys1..tbl1 #else def FROMsys1..tbl2 #endif def WHERE schdid is not null = What I tried is below (but did not work since it captured patterns which had #if nested within the main pattern). $line1 =~ m/#ifndef\s+def(.*?)#else\s+def(.*?)#endif\s+def/isg I thought I knew what you meant, but then I changed my mind! If your input file is, say statement1; #ifdef def1 statement2; #ifdef def2 statement3; #else statement4; #endif statement5; #else statement6; #ifdef def3 statement7; #else statement8; #endif statement9; #endif What is it that you want to capture? Rob -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: nested pattern match
Rob, The input file you described is not correct, since it has #ifdef def2 statement3; #else statement4; #endif nested within another #ifdef ... #else ... #endif. My input file is the output of diff -D def file1 file2 (on unix). This will generate a file which has the following patterns and none of the patterns can be nested within the other: #ifdef #else ... #endif #ifndef #else ... #endif #ifdef #endif #ifndef #endif I need to substitute the above patterns to be read by a home grown program. I encountered a problem due to the following reason. There was: #ifndef def #endif def- Call it sentence1 #ifndef def ... #else def ... #endif def - Call it sentence2 I tried the following line but it matched sentence1 and sentence2 together. I need to match sentence1 and sentence2 seperately. $line1 =~ m/#ifndef\s+def(.*?)#else\s+def(.*?)#endif\s+def/isg For this #ifndef def (...1...) #else def (...2...) #endif def should be matched only if #if is not there within (...1...) and (...2...). Hopefully I have conveyed it more clearly. Thanks, Raghu == Raghupathy wrote: Hi All, I have a text file as shown below. How do I match patterns like the following: Pattern to be matched: = #ifndef def .. (anything except #if) #else def ... (anything except #if) #endif def My Input Data: = #ifndef def DELETE sys1..tbl1 #endif def SELECT col1, col2, col3 #ifndef def FROMsys1..tbl1 #else def FROMsys1..tbl2 #endif def WHERE schdid is not null = What I tried is below (but did not work since it captured patterns which had #if nested within the main pattern). $line1 =~ m/#ifndef\s+def(.*?)#else\s+def(.*?)#endif\s+def/isg I thought I knew what you meant, but then I changed my mind! If your input file is, say statement1; #ifdef def1 statement2; #ifdef def2 statement3; #else statement4; #endif statement5; #else statement6; #ifdef def3 statement7; #else statement8; #endif statement9; #endif What is it that you want to capture? Rob __ Do you Yahoo!? Yahoo! SiteBuilder - Free, easy-to-use web site design software http://sitebuilder.yahoo.com -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: nested pattern match
Raghupathy wrote:
Rob,
The input file you described is not correct, since
it has
#ifdef def2
statement3;
#else
statement4;
#endif
nested within another #ifdef ... #else ... #endif.
My input file is the output of
diff -D def file1 file2 (on unix). This will
generate a file which has the following patterns and
none of the patterns can be nested within the other:
#ifdef #else ... #endif
#ifndef #else ... #endif
#ifdef #endif
#ifndef #endif
I need to substitute the above patterns to be read
by a home grown program.
I encountered a problem due to the following
reason.
There was:
#ifndef def #endif def- Call it sentence1
#ifndef def ... #else def ... #endif def - Call it
sentence2
I tried the following line but it matched sentence1
and sentence2 together. I need to match sentence1 and
sentence2 seperately.
$line1 =~
m/#ifndef\s+def(.*?)#else\s+def(.*?)#endif\s+def/isg
For this
#ifndef def (...1...) #else def (...2...) #endif def
should be matched only if #if is not there within
(...1...) and (...2...).
Hopefully I have conveyed it more clearly.
still not quit sure what you need but try the following:
#!/usr/bin/perl -w
use strict;
my $code =C;
#ifdef debug
debug defined!
#endif debug
#ifndef fork
no fork
no pfork
#else fork
great os
#endif fork
C
while($code =~ /
\#if n? def
\s+
([^\n]+)
(.*?)
(?:
\#else
\s+
\1
(.*?)
)?
\#endif
\s+
\1
/gsx){
my $if = $2;
my $else = $3 || '';
print $1:,$if;
print $1 else: ,$else if($else);
}
__END__
prints:
debug:
debug defined!
fork:
no fork
no pfork
fork else:
great os
not sure if that's what you want.
david
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RE: Nested hash creation help !
Thanks Jose!
I have the hash created and now can see the values
using Data::Dumper but now I an having trouble walking the hashtree.
Trying to walk back out to each leaf value in the tree.
Hash def
$time={$custname}{$custsub}{$site}{$YYMMDDay}{'start'} = $hhmmsss;
This doesn't seem to get anything but $c.
foreach my $c (sort keys %time) {
print Cust $c\n;
foreach my $cs (sort keys %{$time-{$c}}) {
foreach my $s (sort keys %{$time-{$c}-{$cs}}) {
print Site $c.$cs.$s \n
#..etc . next branch . etc
}
}
}
-Original Message-
From: NYIMI Jose (BMB) [mailto:[EMAIL PROTECTED]]
Sent: Monday, January 20, 2003 6:11 AM
To: [EMAIL PROTECTED]; Beginners Perl
Subject: RE: Nested hash creation help !
Afterwards, to see how your nested hash looks like,
try this:
use Data::Dumper;
print Dumper(\%time);
José.
-Original Message-
From: Scot Needy [mailto:[EMAIL PROTECTED]]
Sent: Monday, January 20, 2003 6:50 AM
To: Beginners Perl
Subject: Nested hash creation help !
Hi;
Trying to crate a nested hash from variables parsed out of
log files but
as I am a Beginner Perl' coder it is failing terribly. The
basic question
is given you have 5 variables how would you make a nested hash.
Thanks !
Scot
I hope this is enough code to example my problem.
-- snip --
foreach (@wwwlogs) {
%time=();
($wwwname,$cust,$YYMMDDay) = split('\.',$_);
open (LOG, $_ ) || die Can't open $_!: $! \n;
while (LOG) {
chomp;
# Walk through log file and look for our string.
($pid,$hhmmss,$host,$custname,$custsub,$site,$junk)
= split('\|',$_);
# print(SPLITVARS=
$hhmmss,$host,$custname,$custsub,$site\n);
$time={$custname}={$custsub}={$site}={$YYMMDDay}
= $hhmmss;
} etc etc etc
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RE: Nested hash creation help !
Thanks to Jose and all others who posted.
I now have a working nested hash and a better understanding of them.
Scot
-Original Message-
From: NYIMI Jose (BMB) [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, January 21, 2003 7:34 AM
To: [EMAIL PROTECTED]
Subject: RE: Nested hash creation help !
-Original Message-
From: Scot Needy [mailto:[EMAIL PROTECTED]]
Sent: Monday, January 20, 2003 4:58 PM
To: NYIMI Jose (BMB); Beginners Perl
Subject: RE: Nested hash creation help !
Thanks Jose!
I have the hash created and now can see the values
using Data::Dumper but now I an having trouble walking the
hashtree. Trying to walk back out to each leaf value in the tree.
Hash def
$time={$custname}{$custsub}{$site}{$YYMMDDay}{'start'} = $hhmmsss;
This doesn't seem to get anything but $c.
foreach my $c (sort keys %time) {
print Cust $c\n;
foreach my $cs (sort keys %{$time-{$c}}) {
If you write this $time-{key} that means the variable 'time' is a
'reference to an hash' not an 'hash'.
Since you declared your 'time' beeing an hash as follow: %time=();
You should not be using the arrow notation. Use this intead : $time{key}
If really want to arrow notation, you need to declare 'time' like this :
my $time={};#reference to an anonymous hash
#filling-in as follow
$time-{$custname}{$custsub}{$site}{$YYMMDDay}{'start'} = $hhmmsss;
#dereference stuff
foreach my $c (sort keys %{$time} ) {
bla bla ..
}
HTH,
José.
foreach my $s (sort keys %{$time-{$c}-{$cs}}) {
print Site $c.$cs.$s \n
#..etc . next branch . etc
}
}
}
-Original Message-
From: NYIMI Jose (BMB) [mailto:[EMAIL PROTECTED]]
Sent: Monday, January 20, 2003 6:11 AM
To: [EMAIL PROTECTED]; Beginners Perl
Subject: RE: Nested hash creation help !
Afterwards, to see how your nested hash looks like,
try this:
use Data::Dumper;
print Dumper(\%time);
José.
-Original Message-
From: Scot Needy [mailto:[EMAIL PROTECTED]]
Sent: Monday, January 20, 2003 6:50 AM
To: Beginners Perl
Subject: Nested hash creation help !
Hi;
Trying to crate a nested hash from variables parsed out of
log files
but as I am a Beginner Perl' coder it is failing terribly. The
basic question
is given you have 5 variables how would you make a nested hash.
Thanks !
Scot
I hope this is enough code to example my problem.
-- snip --
foreach (@wwwlogs) {
%time=();
($wwwname,$cust,$YYMMDDay) = split('\.',$_);
open (LOG, $_ ) || die Can't open $_!: $! \n;
while (LOG) {
chomp;
# Walk through log file and look for our string.
($pid,$hhmmss,$host,$custname,$custsub,$site,$junk)
= split('\|',$_);
# print(SPLITVARS= $hhmmss,$host,$custname,$custsub,$site\n);
$time={$custname}={$custsub}={$site}={$YYMMDDay}
= $hhmmss;
} etc etc etc
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in any form) by other persons than the designated
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RE: Nested hash creation help !
Having a quick look, I may say your ploblem can be solved with hash references.
Something like:
my %hash_level1=();
my %hash_level2=();
$hash_level1{'tag'}=\%hash_level2;
To retrieve a value form hash_level2:
my $hash_p= $hash_level1{'tag'};
Return ${$hash_p}{'tag_from_level2'};
Hope it helps,
Duarte
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-Original Message-
From: Scot Needy [mailto:[EMAIL PROTECTED]]
Sent: Monday, January 20, 2003 5:50 AM
To: Beginners Perl
Subject: Nested hash creation help !
Hi;
Trying to crate a nested hash from variables parsed out of log files but
as I am a Beginner Perl' coder it is failing terribly. The basic question
is given you have 5 variables how would you make a nested hash.
Thanks !
Scot
I hope this is enough code to example my problem.
-- snip --
foreach (@wwwlogs) {
%time=();
($wwwname,$cust,$YYMMDDay) = split('\.',$_);
open (LOG, $_ ) || die Can't open $_!: $! \n;
while (LOG) {
chomp;
# Walk through log file and look for our string.
($pid,$hhmmss,$host,$custname,$custsub,$site,$junk) = split('\|',$_);
# print(SPLITVARS= $hhmmss,$host,$custname,$custsub,$site\n);
$time={$custname}={$custsub}={$site}={$YYMMDDay} = $hhmmss;
} etc etc etc
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Re: Nested hash creation help !
Scot Needy wrote:
Hi;
Hello,
Trying to crate a nested hash from variables parsed out of log files but
as I am a Beginner Perl' coder it is failing terribly. The basic question
is given you have 5 variables how would you make a nested hash.
I hope this is enough code to example my problem.
-- snip --
foreach (@wwwlogs) {
%time=();
($wwwname,$cust,$YYMMDDay) = split('\.',$_);
The first argument to split is a regular expression.
my ( $wwwname, $cust, $YYMMDDay ) = split /\./;
open (LOG, $_ ) || die Can't open $_!: $! \n;
while (LOG) {
chomp;
# Walk through log file and look for our string.
($pid,$hhmmss,$host,$custname,$custsub,$site,$junk) = split('\|',$_);
my ( $pid, $hhmmss, $host, $custname, $custsub, $site ) = split
/\|/;
# print(SPLITVARS= $hhmmss,$host,$custname,$custsub,$site\n);
$time={$custname}={$custsub}={$site}={$YYMMDDay} = $hhmmss;
You are using the = operator which is the same as a comma when you
should be using the - operator to dereference hash references.
$time{$custname}-{$custsub}-{$site}-{$YYMMDDay} = $hhmmss;
Which could also be written as:
$time{$custname}{$custsub}{$site}{$YYMMDDay} = $hhmmss;
} etc etc etc
You can simplify things if you store the log file names in @ARGV instead
of @wwwlogs.
@ARGV = @wwwlogs;
my %time;
while ( ) {
my ( $wwwname, $cust, $YYMMDDay ) = split /\./, $ARGV if $. == 1;
chomp;
# Walk through log file and look for our string.
my ( $pid, $hhmmss, $host, $custname, $custsub, $site ) = split
/\|/;
# print(SPLITVARS= $hhmmss,$host,$custname,$custsub,$site\n);
$time{$custname}{$custsub}{$site}{$YYMMDDay} = $hhmmss;
# etc etc etc
if ( eof ) {
close ARGV;
%time = ();
}
}
__END__
John
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RE: Nested hash creation help !
I would be writing this:
#!/usr/bin/perl -w
use strict;
foreach my $logfile (@wwwlogs) {
my %time=();
my ($wwwname,$cust,$YYMMDDay) = split(/\./,$logfile);
open (LOG, $logfile) || die Can't open $logfile : $! \n;
while (LOG) {
chomp;
# Walk through log file and look for our string.
my($pid,$hhmmss,$host,$custname,$custsub,$site,$junk) = split /\|/;
# print(SPLITVARS= $hhmmss,$host,$custname,$custsub,$site\n);
$time{$custname}{$custsub}{$site}{$YYMMDDay}=$hhmmss;
}
close(LOG);
etc etc ...
}
Not tested !
HTH,
José.
-Original Message-
From: Scot Needy [mailto:[EMAIL PROTECTED]]
Sent: Monday, January 20, 2003 6:50 AM
To: Beginners Perl
Subject: Nested hash creation help !
Hi;
Trying to crate a nested hash from variables parsed out of
log files but
as I am a Beginner Perl' coder it is failing terribly. The
basic question
is given you have 5 variables how would you make a nested hash.
Thanks !
Scot
I hope this is enough code to example my problem.
-- snip --
foreach (@wwwlogs) {
%time=();
($wwwname,$cust,$YYMMDDay) = split('\.',$_);
open (LOG, $_ ) || die Can't open $_!: $! \n;
while (LOG) {
chomp;
# Walk through log file and look for our string.
($pid,$hhmmss,$host,$custname,$custsub,$site,$junk)
= split('\|',$_);
# print(SPLITVARS=
$hhmmss,$host,$custname,$custsub,$site\n);
$time={$custname}={$custsub}={$site}={$YYMMDDay}
= $hhmmss;
} etc etc etc
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This e-mail and any attachment thereto may contain information which is confidential
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the designated recipient(s) is prohibited.
If you have received this e-mail in error, please notify the sender either by
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RE: Nested hash creation help !
Afterwards, to see how your nested hash looks like,
try this:
use Data::Dumper;
print Dumper(\%time);
José.
-Original Message-
From: Scot Needy [mailto:[EMAIL PROTECTED]]
Sent: Monday, January 20, 2003 6:50 AM
To: Beginners Perl
Subject: Nested hash creation help !
Hi;
Trying to crate a nested hash from variables parsed out of
log files but
as I am a Beginner Perl' coder it is failing terribly. The
basic question
is given you have 5 variables how would you make a nested hash.
Thanks !
Scot
I hope this is enough code to example my problem.
-- snip --
foreach (@wwwlogs) {
%time=();
($wwwname,$cust,$YYMMDDay) = split('\.',$_);
open (LOG, $_ ) || die Can't open $_!: $! \n;
while (LOG) {
chomp;
# Walk through log file and look for our string.
($pid,$hhmmss,$host,$custname,$custsub,$site,$junk)
= split('\|',$_);
# print(SPLITVARS=
$hhmmss,$host,$custname,$custsub,$site\n);
$time={$custname}={$custsub}={$site}={$YYMMDDay}
= $hhmmss;
} etc etc etc
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Re: Nested hash creation help !
John W. Krahn wrote:
Scot Needy wrote:
Hi;
Hello,
Trying to crate a nested hash from variables parsed out of log
files but
as I am a Beginner Perl' coder it is failing terribly. The basic
question
is given you have 5 variables how would you make a nested hash.
I hope this is enough code to example my problem.
-- snip --
foreach (@wwwlogs) {
%time=();
($wwwname,$cust,$YYMMDDay) = split('\.',$_);
The first argument to split is a regular expression.
my ( $wwwname, $cust, $YYMMDDay ) = split /\./;
But, as it has an implied 'm', any delimiter will do.
The original is fine :)
Cheers,
Rob
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Re: Nested hash creation help !
Scot Needy wrote:
Hi;
Trying to crate a nested hash from variables parsed out of log files
but as I am a Beginner Perl' coder it is failing terribly. The basic
question is given you have 5 variables how would you make a nested
hash.
Thanks !
Scot
I hope this is enough code to example my problem.
-- snip --
foreach (@wwwlogs) {
%time=();
($wwwname,$cust,$YYMMDDay) = split('\.',$_);
open (LOG, $_ ) || die Can't open $_!: $! \n;
while (LOG) {
chomp;
# Walk through log file and look for our string.
($pid,$hhmmss,$host,$custname,$custsub,$site,$junk) =
split('\|',$_); # print(SPLITVARS=
$hhmmss,$host,$custname,$custsub,$site\n);
$time={$custname}={$custsub}={$site}={$YYMMDDay} = $hhmmss;
} etc etc etc
People have offered you some fine corrections to your code, but
I wonder if this is what you really want? The hash is very deeply
nested and is only necessary if you need to access you data this way.
Also I think you may well have multiple times per date to store, so
that subsequent times from the log file will simply overwrite
what you have already. Perhaps this is of some help:
my $custsite = $custname|$custsub|$site;
my $time= $YYMMDDay:$hhmmss;
$time{$custsite}[$i++], $time;
( equivalent to 'push @{$time{$custsite}}, $time' )
i.e. an array of date/times for each customer site.
Don't copy this code verbatim, I'm trying to describe a
data structure rather than write functional code.
Cheers,
Rob
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