Re: Learning regular expressions
On 19 Mar 2003 at 19:31, Chris Benson wrote: [Getting ORA books at a discount as a *.pm member] On Wed, Mar 19, 2003 at 07:06:53PM +0100, Philip Newton wrote: (Presumably only works when ordering directly from ORA.) Yup, I used to have a card with Josette's contact details, ... I'll try to find it. Or via UKUUG if you're in that. Re: UKUUG - not likely, as I'm in Germany :). But if you could dig out the card, I'd appreciate it. Maybe they do the same thing at ORA.de. Cheers, Philip -- Philip Newton [EMAIL PROTECTED]
Re: Learning regular expressions
On Tue, Mar 18, 2003 at 12:41:18PM +, Phil Dobbin ([EMAIL PROTECTED]) wrote: Hey, I've bought thirty-two O'Reilly books as it is ;-) From: Dave Cross [EMAIL PROTECTED] Sent: Tuesday, March 18, 2003 3:51 PM I quick count in the area round my desk at home finds 120 O'Reilly books. There are others at work as well I think. Luis Campos de Carvalho wrote: pedanticHey, Dave, do you work at a Book Store? =-]/pedantic Well my significant other *does* work in a book store - and used to work in computing - and I can only see fifteen O'Reilly books in this room, plus another five in the hallway, [ plus whatever mstevens or Tantrix have would be easily available] Admittedly ten/twelve of those O'Reilly books are on CD but Available for java/perl/C++/web development in London, UK or nearby. Apache FOP, Cocoon, Turbine, Struts,XSL:FO, XML, Tomcat, JSP http://www.OWAL.co.uk/
Re: Learning regular expressions
On 18 Mar 2003 at 14:32, Chris Benson wrote: [ORA books] I blame Josette. You can't turn round without getting a discount: London PerlMounger - get a discount, Tyneside PerlMounger - get a discount, UKUUG member - get a discount, ... How does that work? Just mention I'm a Foo.pm member when placing your order? Seems a bit too easy to me. (Presumably only works when ordering directly from ORA.) Cheers, Philip -- Philip Newton [EMAIL PROTECTED]
Re: Learning regular expressions
On Wed, Mar 19, 2003 at 07:06:53PM +0100, Philip Newton wrote: On 18 Mar 2003 at 14:32, Chris Benson wrote: [ORA books] I blame Josette. You can't turn round without getting a discount: London PerlMounger - get a discount, Tyneside PerlMounger - get a discount, UKUUG member - get a discount, ... How does that work? Just mention I'm a Foo.pm member when placing your order? Yup, they arrive from (whichever publisher Pearson? handles ORA in the UK) in a few days. Seems a bit too easy to me. That's the problem :-) (Presumably only works when ordering directly from ORA.) Yup, I used to have a card with Josette's contact details, ... I'll try to find it. Or via UKUUG if you're in that. -- Chris Benson
RE: Learning regular expressions
Hey - I didn't realise there was a second edition.
Mastering Regular expressions is what I learnt from, found it great.
Gareth
-Original Message-
[mailto:[EMAIL PROTECTED] Behalf Of Mark Fowler
You'd be better off with the 2nd Edition.
O'Reilly: 0-596-00289-0
http://www.oreilly.com/catalog/regex2/
Shouldn't someone be reviewing this for the site?
Mark.
--
#!/usr/bin/perl -T
use strict;
use warnings;
print q{Mark Fowler, [EMAIL PROTECTED],
http://twoshortplanks.com/};
Re: Learning regular expressions
On Mon, 17 Mar 2003, Phil Dobbin wrote:
You can't go wrong with Jeffrey Friedl's `Mastering Regular Expressions'
(O'Reilly: 1-56592-257-3).
You'd be better off with the 2nd Edition.
O'Reilly: 0-596-00289-0
http://www.oreilly.com/catalog/regex2/
Shouldn't someone be reviewing this for the site?
Mark.
--
#!/usr/bin/perl -T
use strict;
use warnings;
print q{Mark Fowler, [EMAIL PROTECTED], http://twoshortplanks.com/};
Re: Learning regular expressions
Quoting Mark Fowler ([EMAIL PROTECTED]): On Mon, 17 Mar 2003, Phil Dobbin wrote: You can't go wrong with Jeffrey Friedl's `Mastering Regular Expressions' (O'Reilly: 1-56592-257-3). You'd be better off with the 2nd Edition. O'Reilly: 0-596-00289-0 http://www.oreilly.com/catalog/regex2/ Shouldn't someone be reviewing this for the site? I just finished reading it (privately). I agree that if you're serious about regexes, you should read this book. The second edition also contains chapters on Java, VB.net, .. Perl is still the main languange of this book though. After reading this book I was able to speed up a regex we're using in production by a factor of 4. Kris,
Re: Learning regular expressions
* Mark Fowler ([EMAIL PROTECTED]) wrote: On Mon, 17 Mar 2003, Phil Dobbin wrote: You can't go wrong with Jeffrey Friedl's `Mastering Regular Expressions' (O'Reilly: 1-56592-257-3). You'd be better off with the 2nd Edition. O'Reilly: 0-596-00289-0 http://www.oreilly.com/catalog/regex2/ Shouldn't someone be reviewing this for the site? *looks down at the ground and shuffles feet nervously* Greg -- *** *** *** Email address has changed to [EMAIL PROTECTED] . Please *** *** update your email address book. *** *** *** Greg McCarroll http://www.mccarroll.org.uk/~gem/ jabber://[EMAIL PROTECTED]
Re: Learning regular expressions
On Tue Mar 18 10:21:20 2003, Mark Fowler wrote: On Mon, 17 Mar 2003, Phil Dobbin wrote: You can't go wrong with Jeffrey Friedl's `Mastering Regular Expressions' (O'Reilly: 1-56592-257-3). You'd be better off with the 2nd Edition. Or you could come to Belfast next Monday and hear Mark Jason Dominus give his Perl Regular Expression Mastery course. -- Marty
Re: Learning regular expressions
On 18/3/03 10:21, Mark Fowler [EMAIL PROTECTED] wrote:
On Mon, 17 Mar 2003, Phil Dobbin wrote:
You can't go wrong with Jeffrey Friedl's `Mastering Regular Expressions'
(O'Reilly: 1-56592-257-3).
You'd be better off with the 2nd Edition.
[...]
Hey, I've bought thirty-two O'Reilly books as it is ;-)
Regards,
Phil.
--
for(reverse(1..100)){$s=($_==1)? '':'s';print$_ bottle$s of beer on the
wall,\n;
print$_ bottle$s of beer,\nTake one down, pass it around,\n;
$_--;$s=($_==1)?'':'s';print$_ bottle$s of beer on the
wall\n\n;}print'*burp*';
Re: Learning regular expressions
On Tue, Mar 18, 2003 at 12:41:18PM +, Phil Dobbin wrote: Hey, I've bought thirty-two O'Reilly books as it is ;-) I'll raise you: (gulp) forty-eight at home[*] including the 1988 (first?) edition of the X11 manuals. I blame Josette. You can't turn round without getting a discount: London PerlMounger - get a discount, Tyneside PerlMounger - get a discount, UKUUG member - get a discount, ... :-) [*] implying an uncounted number at work ... -- Chris Benson
Re: Learning regular expressions
Jonathan Peterson wrote: I assume that this was supposed to be: =~ m/\s*(?:y|(ok))/i I did. But this is hardly easier than 'eq'. Easier for the programmer? Of course not! Heh, when I say better I mean better for the user, and therefore a better bit of software. Programmers are just staff, but users are people :-) I agree that accepting y,Y, my mother is all well and good from a usability standpoint, but I believe that the original context of this thread was simply whether or not regexs are hard and how well they perform (or, conversely, how poorly they perform when they aren't well-formed). To not do so is broken, end of story. It baffles me that some people think in the year 2003 it's OK to have software that does this: I would agree with you on this, but it makes the assumption that we're discussing user-interactions. Funnily enough, my assumption was that 'y' came from some kind of flat-file in which it might be the result of some kind of form input (e.g. radio button) or log data, but I guess that's because I've spent too long working with ETL code and not people. ;) jon -- jon reades fulcrum analytics t: 0870.366.9338 m: 0797.698.7392 f: 0870.888.8880 lower ground floor 2 sheraton street london w1f 8bh
Re: Learning regular expressions
* Chris Benson ([EMAIL PROTECTED]) wrote: On Tue, Mar 18, 2003 at 12:41:18PM +, Phil Dobbin wrote: Hey, I've bought thirty-two O'Reilly books as it is ;-) I'll raise you: (gulp) forty-eight at home[*] including the 1988 (first?) edition of the X11 manuals. I blame Josette. You can't turn round without getting a discount: London PerlMounger - get a discount, Tyneside PerlMounger - get a discount, UKUUG member - get a discount, ... :-) /me sits in the corner looking smug -- *** *** *** Email address has changed to [EMAIL PROTECTED] . Please *** *** update your email address book. *** *** *** Greg McCarroll http://www.mccarroll.org.uk/~gem/ jabber://[EMAIL PROTECTED]
Re: Learning regular expressions
On Tue, Mar 18, 2003 at 12:41:18PM +, Phil Dobbin ([EMAIL PROTECTED]) wrote: Hey, I've bought thirty-two O'Reilly books as it is ;-) I quick count in the area round my desk at home finds 120 O'Reilly books. There are others at work as well I think. Dave... -- Brian: Oh screw Maximilian! Sally: I do. Brian: So do I.
Re: Learning regular expressions
- Original Message - From: Dave Cross [EMAIL PROTECTED] Sent: Tuesday, March 18, 2003 3:51 PM On Tue, Mar 18, 2003 at 12:41:18PM +, Phil Dobbin ([EMAIL PROTECTED]) wrote: Hey, I've bought thirty-two O'Reilly books as it is ;-) I quick count in the area round my desk at home finds 120 O'Reilly books. There are others at work as well I think. pedanticHey, Dave, do you work at a Book Store? =-]/pedantic Sorry, I can't resist... -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Luis Campos de Carvalho Computer Science Student OCP DBA Oracle Unix Sys Admin =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Re: Learning regular expressions
On Tuesday, March 18, 2003 11:29 + Greg McCarroll [EMAIL PROTECTED] wrote: * Mark Fowler ([EMAIL PROTECTED]) wrote: You'd be better off with the 2nd Edition. O'Reilly: 0-596-00289-0 http://www.oreilly.com/catalog/regex2/ Shouldn't someone be reviewing this for the site? *looks down at the ground and shuffles feet nervously* You should have kept quiet, I wasn't going to be naming any names, what with me being the next person on the naughty list :-) If you (and that's you plural, for anyone else who owes a book review) don't have the time to do a thorough review of a book that you've got, then a shorter review of your first impressions, or of a few selected chapters, would still be useful. -- David Cantrell
Re: Learning regular expressions
Work wrote:
snip
if($userinput eq 'y') ## yucky
{
...
}
Uh, why?
If all you care about is the case 'y' then this is a much better and
faster way to determine the truth or falsehood of the statement. It's
also, IMO, the clearest of all.
If you really wanted to handle a couple of differenct options, then how
about:
my %is_ok = ('y' = 1, 'ok' = 1, 'Y' = 1, 'OK' = 1, 'Ok' = 1);
if ($is_ok{$userinput}) {
...
}
or
if ($is_ok{lc($userinput)}) {
...
}
if($userinput =~ /^\s*y|(ok)/i) # nice
{
...
}
Heh, heh, *this* is nice?
I assume that this was supposed to be:
=~ m/\s*(?:y|(ok))/i
But this is hardly easier than 'eq'.
jon
--
jon reades
fulcrum analytics
t: 0870.366.9338
m: 0797.698.7392
f: 0870.888.8880
lower ground floor
2 sheraton street
london w1f 8bh
Re: Learning regular expressions
On Mon, 17 Mar 2003, Jon Reades wrote:
Work wrote:
snip
if($userinput eq 'y') ## yucky
{
...
}
Uh, why?
If all you care about is the case 'y' then this is a much better and
faster way to determine the truth or falsehood of the statement. It's
also, IMO, the clearest of all.
If you really wanted to handle a couple of differenct options, then how
about:
my %is_ok = ('y' = 1, 'ok' = 1, 'Y' = 1, 'OK' = 1, 'Ok' = 1);
if ($is_ok{$userinput}) {
...
}
Because it's annoying when you prefix your input with a space to have it
rejected. I would strongly prefer the regex.
S.
or
if ($is_ok{lc($userinput)}) {
...
}
if($userinput =~ /^\s*y|(ok)/i) # nice
{
...
}
Heh, heh, *this* is nice?
I assume that this was supposed to be:
=~ m/\s*(?:y|(ok))/i
But this is hardly easier than 'eq'.
jon
--
Shevekhttp://www.anarres.org/
I am the Borg. http://design.anarres.org/
Re: Learning regular expressions
- Original Message -
From: Jon Reades [EMAIL PROTECTED]
Sent: Monday, March 17, 2003 12:09 PM
Work wrote:
snip
if($userinput eq 'y') ## yucky
snip
if($userinput =~ /^\s*y|(ok)/i) # nice
{
...
}
Heh, heh, *this* is nice?
I assume that this was supposed to be:
=~ m/\s*(?:y|(ok))/i
But this is hardly easier than 'eq'.
I'm wondering if you're talking about the regular expression concept or
about the REGEXP pattern match weird-look into your code (Perl have bad
presentation/textual representation of regular expression operators?)
Cheers.
Re: Learning regular expressions
On 13/3/03 17:05, Adam C Auden [EMAIL PROTECTED] wrote: On Thu, 13 Mar 2003, Peter Sergeant wrote: This seems to be a recurring theme - regular expressions are hard. This is not my experience. After QBasic, Perl was the first language I learned, and regular expressions were a topic I found very easy (and there were plenty of topics I found hard, I'm sure). I wonder why it is some people find regexes such a mind-twister. Not sure you can give a complete answer to this one, however I for one find regular expressions tricky due to the lack of decent docs available for them - particularly lack of examples to work from. Now I know I should just go and buy a book, however if anyone has any links to sites which they have found of use it would be much appreciated. [...] You can't go wrong with Jeffrey Friedl's `Mastering Regular Expressions' (O'Reilly: 1-56592-257-3). Great read, too. Regards, Phil. -- Arms my only ornament - my only rest, the fight. -- Cervantes, Don Quixote.
Re: Learning regular expressions
I assume that this was supposed to be: =~ m/\s*(?:y|(ok))/i I did. But this is hardly easier than 'eq'. Easier for the programmer? Of course not! Heh, when I say better I mean better for the user, and therefore a better bit of software. Programmers are just staff, but users are people :-) Any program that claims to accept the string y as input meaning 'yes' (where there are limited alternatives, such as 'no' and 'maybe') must also accept at least: y Y yes yes etc.. To not do so is broken, end of story. It baffles me that some people think in the year 2003 it's OK to have software that does this: The program will now analyse the file foo.db. This may take several hours. Type 'Yes' to continue or 'Quit' to abort the operation. y Please enter either 'Yes' or 'Quit' yes please enter either 'Yes' or 'Quit' But I still see rubbish like this all the time. And we wonder why people prefer GUI's ;-) Jon
Re: Learning regular expressions
I assume that this was supposed to be: =~ m/\s*(?:y|(ok))/i I did. But this is hardly easier than 'eq'. Easier for the programmer? Of course not! Heh, when I say better I mean better for the user, and therefore a better bit of software. Programmers are just staff, but users are people :-) Any program that claims to accept the string y as input meaning 'yes' (where there are limited alternatives, such as 'no' and 'maybe') must also accept at least: y Y yes yes etc.. To not do so is broken, end of story. It baffles me that some people think in the year 2003 it's OK to have software that does this: The program will now analyse the file foo.db. This may take several hours. Type 'Yes' to continue or 'Quit' to abort the operation. y Please enter either 'Yes' or 'Quit' yes please enter either 'Yes' or 'Quit' But I still see rubbish like this all the time. And we wonder why people prefer GUI's ;-) Jon
Re: Learning regular expressions
On Mon, Mar 17, 2003 at 03:24:05PM +, Shevek wrote:
On Mon, 17 Mar 2003, Jon Reades wrote:
Work wrote:
snip
if($userinput eq 'y') ## yucky
{
...
}
Uh, why?
If all you care about is the case 'y' then this is a much better and
faster way to determine the truth or falsehood of the statement. It's
also, IMO, the clearest of all.
If you really wanted to handle a couple of differenct options, then how
about:
my %is_ok = ('y' = 1, 'ok' = 1, 'Y' = 1, 'OK' = 1, 'Ok' = 1);
if ($is_ok{$userinput}) {
...
}
Because it's annoying when you prefix your input with a space to have it
rejected. I would strongly prefer the regex.
If all you care about is that there *is* a 'y', wouldn't index() solve
that problem (and possibly be more efficient than a regex?)
Or did someone mention that already and I'm just in desperate need of
sleep?
dha
--
David H. Adler - [EMAIL PROTECTED] - http://www.panix.com/~dha/
It's amazing what giant mutant ants that are the result of Man's
dabbling with the power of atomic energy can accomplish when they set
themselves to the task.- Mark Rogaski
Re: Learning regular expressions
On Thu, 13 Mar 2003, Adam C Auden wrote:
Not sure you can give a complete answer to this one, however I for one
find regular expressions tricky due to the lack of decent docs available
for them - particularly lack of examples to work from.
The perlre the traditional documentation came with Perl isn't really a
beginers guide or a tutorial. For that you need to see the perlrequick
guide that ships with perl 5.8.0.
http://search.cpan.org/author/JHI/perl-5.8.0/pod/perlrequick.pod
Then you need to go onto the full blown tutorial that is perlretut
http://search.cpan.org/author/JHI/perl-5.8.0/pod/perlretut.pod
All praise Mark Kvale for his hard work here.
Mark.
--
#!/usr/bin/perl -T
use strict;
use warnings;
print q{Mark Fowler, [EMAIL PROTECTED], http://twoshortplanks.com/};
Re: Learning regular expressions
I think that Regexps are hard to learn because the most part of the
folks
that aren't too much scared to learn it just lack the essential and
unavoidable compiler theory where regexp lays its foundations. IMHO, its
simply impossible learn good quality regexp use unless you have good
regular
grammars theory before.
No, that's WRONG. Again, I can only give myself as an example, but, I
had no compiler theory or regular grammars theory. Regular expressions
MAKE SENSE - in (again) my humble experience, it tends to be people who
started with C or somesuch language who have the most difficulty with
them. Go figure.
I agree that regexps seem to 'click' quite rapidly with some people, and
simply remain opaque for a long time with other people. I'm not sure why
this is. The owl book is excellent, but it also tends to make people think
These regexps are really powerful, but really complex - I'll live without
them.
I currently spend a lot of time trying to get Java programmers to use more
regexps. They all love the power and ability they have, but find them hard
to debug and so tend not to use them, or get frustrated easily. Java's poor
implementation* doesn't help.
However, I disagree that you need to understand the magic bahind regexps to
use them. The main strengths of regexps, esp. in their Perl implementation
is easy of use:
if($userinput eq 'y') ## yucky
{
...
}
if($userinput =~ /^\s*y|(ok)/i) # nice
{
...
}
Later, the expert user can start to learn more about how the engine works,
in order to craft more complex regexps.
*Using the various add on libraries for Java 1.2, which are either feature
poor (apache) or just really annoying in a stupid java-y way(gnu).
Re: Learning regular expressions
Work wrote:
if($userinput =~ /^\s*y|(ok)/i) # nice
{
...
}
Going some way to prove that regexps are complicated (for me, anyway), this does
not do what I thought it would.
/foo|bar/ matches foo or bar, obviously.
/foo|(bar)/ (as in the yes/ok case above) matches totally different stuff.
Although I've only been using regexps for 4+ years, and don't remember seeing
this behaviour before. If I have seen it, I must have spurned it, thinking I
must use parentheses better than that.
Jasper
--
We got Deathstar (Deathstar),
We got Deathstar (Deathstar),
We got Deathstar (Deathstar),
And you know that we got it.
Re: Learning regular expressions
Jasper McCrea wrote:
Work wrote:
if($userinput =~ /^\s*y|(ok)/i) # nice
{
...
}
Going some way to prove that regexps are complicated (for me, anyway), this does
not do what I thought it would.
/foo|bar/ matches foo or bar, obviously.
/foo|(bar)/ (as in the yes/ok case above) matches totally different stuff.
Never mind, I was confused, as usual. I didn't think it could possibly be
working as (I thought it was) intended.
But it sort of proves the point, anyway, in that Mr Peterson wrote his regexp
wrong.
If he didn't mean
/^\s*(y|ok)/i
I apologise.
Jasper
--
$='';{split//,ajpsa onhtrep re lahkcre}foreach(0..$#_){
unless($_%2){$_[$_]^=$_[++$_]^=$_[--$_]^=$_[++$_]}}print@_\n
Re: Learning regular expressions
- Original Message - From: Work [EMAIL PROTECTED] Sent: Friday, March 14, 2003 8:02 AM [...] its foundations. IMHO, its simply impossible learn good quality regexp use unless you have good regular grammars theory before. No, that's WRONG. Again, I can only give myself [...] Regular expressions MAKE SENSE - in (again) my humble experience, it tends to be people who started with C [...] I agree that regexps seem to 'click' quite rapidly with some people, and simply remain opaque for a long time with other people. I'm not sure why this is. The owl book is excellent, but it also tends to make people think These regexps are really powerful, but really complex - I'll live without them. Well, you're right: I have seen folks that just can't use regexp because they don't have clicked yet... pretty sad, I think. I currently spend a lot of time trying to get Java programmers to use more regexps. They all love the power and ability they have, but find them hard to debug and so tend not to use them, or get frustrated easily. Java's poor implementation* doesn't help. Maybe the frustration can be avoided with a little quick'n'dirty compiler theory. This will make regexps easyer to debug, too, because you will start to understand the internals. Try the Aho, Sethi Ullman's Dragon Book (Compilers: Principles, Techniques and Tools), chapters one, two and three. http://www.amazon.co.uk/exec/obidos/ASIN/0201100886/qid=1047649342/sr=1-1/re f=sr_1_3_1/026-0411912-1523638 However, I disagree that you need to understand the magic bahind regexps to use them. The main strengths of regexps, esp. in their Perl implementation is easy of use[...] Ok, ok. =-] You're right. What you don't know don't hurts you Later, the expert user can start to learn more about how the engine works, in order to craft more complex regexps. This is essential to use the full power of regular expression. -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Luis Campos de Carvalho Computer Science Student OCP DBA Oracle Unix Sys Admin =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Re: Learning regular expressions
But it sort of proves the point, anyway, in that Mr Peterson wrote his regexp wrong. Yup. If he didn't mean /^\s*(y|ok)/i Yeah, that's what I wanted to write. Stupid precedence rules - Perl didn't do what I meant! :-P However, I suggest that the debug cycle incurred by mis-use of regexps as I just did is still preferable to the mis-funcationality that would have been implemented otherwise. Inadequate user input checking still plagues computer applications, and good use of regexps would go some way to helping this.
Re: Learning regular expressions
On Thu, Mar 13, 2003 at 04:24:16PM +, Peter Sergeant wrote: I wonder why it is some people find regexes such a mind-twister. Trying to run before they can walk? Some of the new stuff confuses the hell out of me still, but then almost all my regex needs could be fulfilled even by perl4. I mostly use 'em as a glorified index(). Because I'm lazy. -- Lord Protector David Cantrell | http://www.cantrell.org.uk/david [OS X] appeals to me as a monk, a user, a compiler-of-apps, a sometime coder, and an easily amused primate with a penchant for those that are pretty, colorful, and make nice noises. -- Dan Birchall, in The Monastery
Re: Learning regular expressions
On Thu, 13 Mar 2003, Peter Sergeant wrote: If you've never heard of grep, glob, split, local/gmtime, unlink, STDIN, ARGV, ... or seen a regular expression, it's all pretty bewildering. Even if you have, there's all the chop/chomp/splice/... cuteness to confuse. This seems to be a recurring theme - regular expressions are hard. This is not my experience. After QBasic, Perl was the first language I learned, and regular expressions were a topic I found very easy (and there were plenty of topics I found hard, I'm sure). I wonder why it is some people find regexes such a mind-twister. I think there are two causes of this : - people don't see a regex as a function (something familar to every language) they see it as some kind of magic and fear it because it is different to what they have done before. - some of the newer (weaker ;) generation lack practice of the traditional problem space that programming has applied to - processing text and data, I think I can program quite well because I find pattern matching and finding relatively easy so regular expressions make perfect sense, newer programmers focus on mouse clicks, using objects and xml to get what they want out of an xml structure or using a cursor with methods to fetch data. The latter are the kind of people who are used to perhaps building ASP type pages where the programming consists of calling a load of functions inside some html, no structure, no text handling - and they do have to write application logic its usually horrible twisted spagetti or embedded into stored_procedures in even more hideous code. A. -- Aaron J Trevena - Perl Hacker, Kung Fu Geek, Internet Consultant AutoDia --- Automatic UML and HTML Specifications from Perl, C++ and Any Datasource with a Handler. http://droogs.org/autodia
Re: Learning regular expressions
On Thu, 13 Mar 2003, Peter Sergeant wrote: This seems to be a recurring theme - regular expressions are hard. This is not my experience. After QBasic, Perl was the first language I learned, and regular expressions were a topic I found very easy (and there were plenty of topics I found hard, I'm sure). I wonder why it is some people find regexes such a mind-twister. Not sure you can give a complete answer to this one, however I for one find regular expressions tricky due to the lack of decent docs available for them - particularly lack of examples to work from. Now I know I should just go and buy a book, however if anyone has any links to sites which they have found of use it would be much appreciated. Other then this, whilst regular expressions can be very powerful tools, they are not the most accessible (Write Once, Read Never is often the case for particularly complex ones) which makes the routine of reading other people's code to learn how it works a trickier one to approach. Having spent most of today wielding sed I think I'm slowly getting the hang of them, but my knowledge is only a small subset I am sure. RegExs are a brick wall I will continue to bash my head against, however I don't see the learning curve getting any easier. A. -- aca114
Re: Learning regular expressions
On Thu, Mar 13, 2003 at 04:24:16PM +, Peter Sergeant wrote: This seems to be a recurring theme - regular expressions are hard. This is not my experience. After QBasic, Perl was the first language I aol (apart from the qbasic bit) -- Lusercop.net - LARTing Lusers everywhere since 2002
Re: Learning regular expressions
On Thu, 13 Mar 2003, Peter Sergeant wrote: [...] I wonder why it is some people find regexes such a mind-twister. From: Adam C Auden [EMAIL PROTECTED] Sent: Thursday, March 13, 2003 2:05 PM Not sure you can give a complete answer to this one, however I for one find regular expressions tricky due to the lack of decent docs available for them - particularly lack of examples to work from. I disagree. Regexps are quite well documented. There is even a manpage exclusively dedicated to it. =-] I think that Regexps are hard to learn because the most part of the folks that aren't too much scared to learn it just lack the essential and unavoidable compiler theory where regexp lays its foundations. IMHO, its simply impossible learn good quality regexp use unless you have good regular grammars theory before. Other then this, whilst regular expressions can be very powerful tools, they are not the most accessible (Write Once, Read Never is often the case for particularly complex ones) which makes the routine of reading other people's code to learn how it works a trickier one to approach. Sorry, I disagree on you again. =-] Folks that write regexps and do not optimize source code for reading (e.g.: using the 'x' option) are building a maintenance nightmare. Regexps are as powerfull as dynamite: you should handle them with care, or you will blow everything up soon or later. =-] -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Luis Campos de Carvalho Computer Science Student OCP DBA Oracle Unix Sys Admin =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Re: Learning regular expressions
I disagree. Regexps are quite well documented. There is even a manpage exclusively dedicated to it. =-] Though actually most of the docs used to be split between perlop and perlre, neither of which are friendly pieces of text. I believe this situation has ameliorated a little, but, certainly the docs were traditionally kinda sucky. I think that Regexps are hard to learn because the most part of the folks that aren't too much scared to learn it just lack the essential and unavoidable compiler theory where regexp lays its foundations. IMHO, its simply impossible learn good quality regexp use unless you have good regular grammars theory before. No, that's WRONG. Again, I can only give myself as an example, but, I had no compiler theory or regular grammars theory. Regular expressions MAKE SENSE - in (again) my humble experience, it tends to be people who started with C or somesuch language who have the most difficulty with them. Go figure. +Pete -- Much may be made of a Scotchman, if he be caught young. -- Samuel Johnson
