RE: One line variable declaration with multiple conditions
Dan Muey wrote:
Howdy list.
I'm trying to one lineify this:
my $guts = $firstchoice || '';
if(!$guts $use_second_choice_if_first_is_empty) {
$guts = $secondchoice;
}
Basically
my $guts = $firstchoice || $secondchoic || '';
Would be perfect except I only want to let it use $seconchoice if
$use_second_choice_if_first_is_empty has a true value. This
does not
work like I want but illustrates the goal if you read it
our loud. my
$guts = $firstchoice || $secondchoic if
$use_second_choice_if_first_is_empty || '';
Is that possible to do with one line?
TIA
Dan
I don't know Dan, it looks like you already said it clearly
in the first cnstruct above. I would not discard that
It is clear but doesn't do what I'm getting at.
The seconde one *reads* like it but does not function how it *reads*.
I want to assign it a value.
If that value is missing I want to assign a second value, and
here's the tricky part, if a particular variable says it is ok to.
Othyerwise it should be empty.
clarity without good reason. Isn't it more important to say
what you mean than to tuck it all up tightly?
Except I need to do this to about ten variabels all in a row.
Which gives me 10 lines with Bob's way and 40 with my very
first example. Boo for that! :)
Joseph
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RE: One line variable declaration with multiple conditions
Dan Muey wrote: BTW - I'm not really using these variable names, only using them here ot help clarify my goal. Why not? They looked very good to me, at least in the context of the question at hand. One of the best aspects of In context yes, but the really really long was a bit much! Perl, IMHO, is that it allows you to just say what you mean. I think people take far too little advantage of this boon. It definitely does help, especially after you look at the code again a while later and you're trying to remember what you were doing, or Someone else is tryign to decifer it later. Thanks for bringing that point out. Bob's woprks perfect I agree. It is quite elegant, with no loss of clarity. Joseph -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
Re: One line variable declaration with multiple conditions
On Jan 8, 2004, at 7:45 AM, Dan Muey wrote:
[..]
Except I need to do this to about ten variabels all in a row.
Which gives me 10 lines with Bob's way and 40 with my very
first example. Boo for that! :)
[..]
Have you thought about a simplification process?
One of the tricks I do is say
my ($var1,$var2,$var3,$var4) = ('' , '' , '', '');
This way I have declared them and initialized them,
so that they will not bounce with that 'use of undefined
var at line X error.
This way when you get down to
my $guts = ($use_second_choice)? $var2:$var1;
you don't need to worry about the additional bit of
making sure that it is
my $guts = ($use_second_choice)? $var2: $var1 || '';
Just a thought to think...
ciao
drieux
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RE: One line variable declaration with multiple conditions
On Jan 8, 2004, at 7:45 AM, Dan Muey wrote:
[..]
Except I need to do this to about ten variabels all in a row. Which
gives me 10 lines with Bob's way and 40 with my very first example.
Boo for that! :)
[..]
Have you thought about a simplification process?
One of the tricks I do is say
my ($var1,$var2,$var3,$var4) = ('' , '' , '', '');
This way I have declared them and initialized them,
so that they will not bounce with that 'use of undefined
var at line X error.
This way when you get down to
my $guts = ($use_second_choice)? $var2:$var1;
you don't need to worry about the additional bit of
making sure that it is
my $guts = ($use_second_choice)? $var2: $var1 || '';
Wouldn't the || '' apply to $guts and not the use of uninitialized $var1,$var2,etc...
Anyway?
Just a thought to think...
The vars to be assigned ($var1, $var2,etc...) come from a
database query so they are handled already earlier. So how
they are declared are irrelevant to the issue. (Yes they must be
initialized for a warnings safe environment and they are, just
assume that they are so the issue is not clouded by where they come from.)
The other thing the tricky part is:
I only want to assign it $var2 if($use_second_choice !$var1)
I think the way you're doing it will asign it $value2 if $use_second_choice
regardless of if $var1 has a value or not.
So :
No matter what if $var1 has a value then assign $guts that value.
If $var 1 is empty and $use_second_value then assign it $var2
Other wise it shoufl be empty.
Bill's method work perfectly, namely:
$var1,$var2 and $ues_2 are declared and set earlier via a
DB query. So don't worry about where they are coming from.
my $value = $var1 || ($use_2 $var2) || '';
So $value gets set to $var1 no matter what if($var1).
If it's not then it goes to the next step and is asking :Ok $var1 has no
value do you want to use $var2 ? if Yes give it $var2 if not say sorry
I can't help you and on the the next || which says ok you shall receive
from the variable gods '' nothing!
OR in longer terms:
my $guts = ''; # so that at least it has something assigned even if it's nothgin. :)
if($var1) { $guts = $var1; }
elsif($use_var2_if_var1_is_empty) { $guts = $var2; }
See what I'm trying to get at?
Bob's example does this quite perfectly, thanks again Bob!\
Dmuey
ciao
drieux
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Re: One line variable declaration with multiple conditions
On Jan 8, 2004, at 10:38 AM, Dan Muey wrote:
[..]
The vars to be assigned ($var1, $var2,etc...) come from a
database query so they are handled already earlier. So how
they are declared are irrelevant to the issue. (Yes they must be
initialized for a warnings safe environment and they are, just
assume that they are so the issue is not clouded by where they come
from.)
I think I better see the context at this point.
note, as I presume you did
my ($var1,$var2,$var3,$var4) = ('', 'bob', '', '');
print ($var1,$var2,$var3,$var4)\n;
($var1,$var2,$var3,$var4) = db_query();
print ($var1,$var2,$var3,$var4)\n;
#
#
sub db_query
{
my ($input) = @_;
('',$input);
} # end of db_query
will explode on the second print statement - since the
little db_query() returned only two of four possible variables,
and in this case three of them are undef and thus 'resetting' the
values.
[..]
hence the problem being that mere 'initialization' alone
is not going to 'save the day'.
Bob's example does this quite perfectly, thanks again Bob!\
yeah, I can see that now.
ciao
drieux
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RE: One line variable declaration with multiple conditions
I think I better see the context at this point.
note, as I presume you did
The issue is resolved, but for the die hards here goes...
I'm wanted to figure out my method of attack before I did the whole
thing but here is an example that will illustrate the basic idea hopefully:
#!/usr/bin/perl -w
use strict;
use DBI;
my $dbh-connect(...) or die ;
my ($def_foo,$def_bar,$def_joe,$def_mama) = $dbh-selectrow_array(SELECT
Foo,Bar,Joe,Mama FROM Default_Settings);
for(@{$dbh-selectall_arrayref(SELECT Foo,Bar,Joe,Mama,Use_Def FROM Whatsits WHERE
Blah=1234)}) {
my ($foo,$bar,$joe,$mama,$use_def) = @{$_};
my $foo_use = $foo || ($use_def $def_foo) || '';
my $bar_use = $bar || ($use_def $def_bar) || '';
my $joe_use = $joe || ($use_def $def_joe) || '';
my $mama_use = $mama || ($use_def $def_mama) || '';
print $foo_use - $bar_use $joe_use $mam_use\n; # or do whatever with it
}
$dbh-disconnect();
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One line variable declaration with multiple conditions
Howdy list.
I'm trying to one lineify this:
my $guts = $firstchoice || '';
if(!$guts $use_second_choice_if_first_is_empty) {
$guts = $secondchoice;
}
Basically
my $guts = $firstchoice || $secondchoic || '';
Would be perfect except I only want to let it use $seconchoice if
$use_second_choice_if_first_is_empty has a true value.
This does not work like I want but illustrates the goal if you read it our loud.
my $guts = $firstchoice || $secondchoic if $use_second_choice_if_first_is_empty || '';
Is that possible to do with one line?
TIA
Dan
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RE: One line variable declaration with multiple conditions
Dan Muey wrote:
Howdy list.
I'm trying to one lineify this:
my $guts = $firstchoice || '';
if(!$guts $use_second_choice_if_first_is_empty) { $guts =
$secondchoice; }
Basically
my $guts = $firstchoice || $secondchoic || '';
Would be perfect except I only want to let it use
$seconchoice if $use_second_choice_if_first_is_empty has a true value.
This does not work like I want but illustrates the goal if
you read it our loud.
my $guts = $firstchoice || $secondchoic if
$use_second_choice_if_first_is_empty || '';
Is that possible to do with one line?
$first || ($use_second $second) || '';
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Re: One line variable declaration with multiple conditions
Howdy list.
I'm trying to one lineify this:
my $guts = $firstchoice || '';
if(!$guts $use_second_choice_if_first_is_empty) {
$guts = $secondchoice;
}
Basically
my $guts = $firstchoice || $secondchoic || '';
Would be perfect except I only want to let it use $seconchoice if
$use_second_choice_if_first_is_empty has a true value.
This does not work like I want but illustrates the goal if you read it
our loud.
my $guts = $firstchoice || $secondchoic if
$use_second_choice_if_first_is_empty || '';
Is that possible to do with one line?
TIA
Dan
Seems like the ternary operator should set you up... perldoc perlop look
for Conditional Operator...
my $guts = (($firstchoice ne '') ? $firstchoice : (($firstchoice eq '')
? $secondchoice : ''));
Though there may be a better way using some combination of ||= or am I
misunderstanding you completely?
http://danconia.org
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Re: One line variable declaration with multiple conditions
On Jan 7, 2004, at 2:20 PM, Dan Muey wrote: Is that possible to do with one line? technically no, because you needed my ($firstchoice, $use_second_choice_if_first_is_empty); my $secondchoice = 's2'; then you can do my $guts = ($use_second_choice_if_first_is_empty)? $secondchoice : $firstchoice || ''; ciao drieux --- -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
RE: One line variable declaration with multiple conditions
On Jan 7, 2004, at 2:20 PM, Dan Muey wrote: Is that possible to do with one line? technically no, because you needed my ($firstchoice, $use_second_choice_if_first_is_empty); my $secondchoice = 's2'; Sorry, I figured we could assume they were declared earlier so as not to muck up the screen and it wouldn't really change the question or answer. then you can do my $guts = ($use_second_choice_if_first_is_empty)? $secondchoice : $firstchoice || ''; Nice. 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 -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
RE: One line variable declaration with multiple conditions
Howdy list.
I'm trying to one lineify this:
my $guts = $firstchoice || '';
if(!$guts $use_second_choice_if_first_is_empty) {
$guts = $secondchoice;
}
Basically
my $guts = $firstchoice || $secondchoic || '';
Would be perfect except I only want to let it use $seconchoice if
$use_second_choice_if_first_is_empty has a true value.
This does not work like I want but illustrates the goal if
you read it
our loud.
my $guts = $firstchoice || $secondchoic if
$use_second_choice_if_first_is_empty || '';
Is that possible to do with one line?
TIA
Dan
Seems like the ternary operator should set you up... perldoc
perlop look for Conditional Operator...
my $guts = (($firstchoice ne '') ? $firstchoice :
(($firstchoice eq '') ? $secondchoice : ''));
Thanks! I'll try each of these suggestions and maybe Benchmark them for grins.
Though there may be a better way using some combination of
||= or am I misunderstanding you completely?
http://danconia.org
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RE: One line variable declaration with multiple conditions
Dan Muey wrote:
Howdy list.
I'm trying to one lineify this:
my $guts = $firstchoice || '';
if(!$guts $use_second_choice_if_first_is_empty) {$guts =
$secondchoice; }
Basically
my $guts = $firstchoice || $secondchoic || '';
Would be perfect except I only want to let it use $seconchoice if
$use_second_choice_if_first_is_empty has a true value. This
does not
work like I want but illustrates the goal if you read it our loud.
my $guts = $firstchoice || $secondchoic if
$use_second_choice_if_first_is_empty || '';
Is that possible to do with one line?
$first || ($use_second $second) || '';
Short and sweet! Thanks Bob!
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RE: One line variable declaration with multiple conditions
Howdy list.
I'm trying to one lineify this:
my $guts = $firstchoice || '';
if(!$guts $use_second_choice_if_first_is_empty) {
$guts = $secondchoice;
}
Basically
my $guts = $firstchoice || $secondchoic || '';
Would be perfect except I only want to let it use $seconchoice if
$use_second_choice_if_first_is_empty has a true value.
This does not work like I want but illustrates the goal if
you read it
our loud.
my $guts = $firstchoice || $secondchoic if
$use_second_choice_if_first_is_empty || '';
Is that possible to do with one line?
TIA
Dan
Seems like the ternary operator should set you up... perldoc
perlop look for Conditional Operator...
my $guts = (($firstchoice ne '') ? $firstchoice :
(($firstchoice eq '') ? $secondchoice : ''));
Except I only want to assign $secondchoice to it if
$use_second_choice_if_first_is_empty is true.
BTW - I'm not really using these variable names, only using them here ot help clarify
my goal.
Bob's woprks perfect and I havn';t tied Driex's as I have to leave right now.
I'm going to benchmark them and see if there is any performance gain in either, though
I doubt it.
Thanks
Though there may be a better way using some combination of
||= or am I misunderstanding you completely?
http://danconia.org
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Re: One line variable declaration with multiple conditions
Dan Muey wrote:
Howdy list.
I'm trying to one lineify this:
my $guts = $firstchoice || '';
if(!$guts $use_second_choice_if_first_is_empty) {
$guts = $secondchoice;
}
Basically
my $guts = $firstchoice || $secondchoic || '';
Would be perfect except I only want to let it use $seconchoice if
$use_second_choice_if_first_is_empty has a true value.
This does not work like I want but illustrates the goal if you read it our loud.
my $guts = $firstchoice || $secondchoic if $use_second_choice_if_first_is_empty ||
'';
Is that possible to do with one line?
TIA
Dan
I don't know Dan, it looks like you already said it clearly in the first cnstruct
above. I would not discard that clarity
without good reason. Isn't it more important to say what you mean than to tuck it all
up tightly?
Joseph
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Re: One line variable declaration with multiple conditions
Dan Muey wrote: BTW - I'm not really using these variable names, only using them here ot help clarify my goal. Why not? They looked very good to me, at least in the context of the question at hand. One of the best aspects of Perl, IMHO, is that it allows you to just say what you mean. I think people take far too little advantage of this boon. Bob's woprks perfect I agree. It is quite elegant, with no loss of clarity. Joseph -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
