Re: Turn off $ anchor greedy behavior
Date sent: Fri, 17 Apr 2009 18:26:17 -0700 (PDT) From: oryann9 orya...@yahoo.com Subject:Re: Turn off $ anchor greedy behavior To: Perl Beginners beginners@perl.org Perl sucks...go Ruby...I did and I am much happier! Good for you. I'm not sure what are you doing here then though. I was forced to use Ruby for some time. No thanks! Jenda = je...@krynicky.cz === http://Jenda.Krynicky.cz = When it comes to wine, women and song, wizards are allowed to get drunk and croon as much as they like. -- Terry Pratchett in Sourcery -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: Turn off $ anchor greedy behavior
Perl sucks...go Ruby...I did and I am much happier! - Original Message From: Michael Alipio daem0n...@yahoo.com To: Perl Beginners beginners@perl.org; John W. Krahn jwkr...@shaw.ca Sent: Tuesday, April 14, 2009 10:06:39 AM Subject: Re: Turn off $ anchor greedy behavior Aha, found it.. The split returned a list and you've just sliced it. giving [-1] means the list will start running through the elements backwards. --- On Tue, 4/14/09, Michael Alipio daem0n...@yahoo.com wrote: From: Michael Alipio daem0n...@yahoo.com Subject: Re: Turn off $ anchor greedy behavior To: Perl Beginners beginners@perl.org, John W. Krahn jwkr...@shaw.ca Date: Tuesday, April 14, 2009, 10:02 PM Or use split and return the last field: $ perl -le' my $string = boy, pig, 123, 123:412adbd, d0g, lajdlf134_ lkadsf !234,\n; my $value = ( split /,\s+/, $string )[ -1 ]; Another mind bogling example... :-) I thought I would do: my @value = ( split /,\s+/, $string ); print $value[6]; How could your example, have printed the last field using [ -1 ]? Can I also print say, the 3rd field using this trick? print $value; ' lajdlf134_ lkadsf !234 John -- Those people who think they know everything are a great annoyance to those of us who do.-- Isaac Asimov -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/ -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/ -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/ -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: Turn off $ anchor greedy behavior
On Fri, Apr 17, 2009 at 21:26, oryann9 orya...@yahoo.com wrote: Perl sucks...go Ruby...I did and I am much happier! snip I looked at Ruby. You couldn't pay me to go back to a language that uses a stupid visual pun for a concatenation operator or forces me to cast variables into different types. 11 + 5 is 16 not a type error. -- Chas. Owens wonkden.net The most important skill a programmer can have is the ability to read. -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Turn off $ anchor greedy behavior
Michael Alipio daem0n...@yahoo.com asked:
I have a $string that is separated by , and space;
boy, pig, 123, 123:412adbd, d0g, lajdlf134_ lkadsf !234,
Now I want to capture the string(s) between last two commas. It consists
of anything upto 32 characters. that is, right after d0g,\s+ up to the
last character before the last comma at the end of the line.
#!/usr/bin/perl -w
use strict;
my $string = 'boy, pig, 123, 123:412adbd, d0g, lajdlf134_ lkadsf !234,';
if( $string =~ m/,\s*([^,]*),[^,]*$/ ){
print $1\n;
}
__END__
Depending on the input data size it might worthwhile to look at rindex() and
substr() instead of using a RE.
HTH,
Thomas
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Re: AW: Turn off $ anchor greedy behavior
my $string = 'boy, pig, 123, 123:412adbd, d0g,
lajdlf134_ lkadsf !234,';
if( $string =~ m/,\s*([^,]*),[^,]*$/ ){
print $1\n;
}
How could you guys write this so simple? My regexp was twice this long.
the regexp after \s* tells perl to match anything (0 or more) that is not a
comma, right? how come it did not match pig? pig is also followed by comma,
right? so pig should be captured by ([^,]*), right? I guess perl really looks
for a match starting from the end of the line.
The string actually looks like this:
ABCD1:5C, 2009-04-14 13:01:24, 2009-04-14, 5, 23, ABC, , , -1, 187, 0, 1.2.3.4,
20, lkasd123 as_!23:s @12ff,
My Regexp looks like this:
/\.\s+\d+,\s+\d+,\s+(.*),$/
It matches from the comma at the end of the line up to .4 when you go
backwards. By going as far as this, I can be assured that perl won't find any
more match, but the regexp looks ugly.
What is wrong with my version?
I think if in the future, if perl finds a line which is not ending in a pattern
exactly like my regexp then it will fail, however yours i guess won't.
__END__
Depending on the input data size it might worthwhile to
look at rindex() and substr() instead of using a RE.
HTH,
Thomas
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Turn off $ anchor greedy behavior
Hi, I have a $string that is separated by , and space; boy, pig, 123, 123:412adbd, d0g, lajdlf134_ lkadsf !234, Now I want to capture the string(s) between last two commas. It consists of anything upto 32 characters. that is, right after d0g,\s+ up to the last character before the last comma at the end of the line. if I do something like (my $value) = $_ ~= /,\s+(.*),\s+$/; $value would start matching from pig because when I used $ and it looked back, the first thing it would match is , pig upto the end of the line I wonder how you could match only the pattern which is nearest to the end of the line having used $ anchor. To get around this, I could split the lines push each comma delimited string into an array and finally print the last element which is a lot of work to do. Is there some sort of turning of greedy behavior of the $ anchor? -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: AW: Turn off $ anchor greedy behavior
Michael Alipio daem0n...@yahoo.com asked:
my $string = 'boy, pig, 123, 123:412adbd, d0g,
lajdlf134_ lkadsf !234,';
if( $string =~ m/,\s*([^,]*),[^,]*$/ ){
print $1\n;
}
How could you guys write this so simple? My regexp was twice this long.
Lots of practice? ;-)
the regexp after \s* tells perl to match anything (0 or more) that is not
a comma, right? how come it did not match pig? pig is also followed by
comma, right? so pig should be captured by ([^,]*), right? I guess perl
really looks for a match starting from the end of the line.
That would be cool, right? No, my RE is says, I want a comma and maybe some
whitespace after it, then I'll capture all of the following stuff that's not a
comma, then I want another comma and possibly some more stuff that's not a
comma right before the end of the line.
Perl's RE engine starts out by looking at , pig (capturing pig) but the
part where I said no further comma before the end of the line prevents it
from matching, since there's a comma after 123 but before the end of the
string. For the same reasons it fails to match at 123, 123:... and d0g.
That's why I think that a classic C approach using rindex() and substr()
might be faster in your case:
#!/usr/bin/perl -w
use strict;
my $string = 'boy, pig, 123, 123:412adbd, d0g, lajdlf134_ lkadsf !234,';
my $rightComma = rindex( $string, ',' ) - 1;
my $leftComma = rindex( $string, ',', $rightComma );
print substr( $string, $leftComma + 2, $rightComma - $leftComma ), \n;
__END__
HTH,
Thomas
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Re: Turn off $ anchor greedy behavior
Michael Alipio wrote: Hi, Hello, Subject: Turn off $ anchor greedy behavior Anchors are not greedy. Anchors don't even match characters. I have a $string that is separated by , and space; boy, pig, 123, 123:412adbd, d0g, lajdlf134_ lkadsf !234, Now I want to capture the string(s) between last two commas. It consists of anything upto 32 characters. that is, right after d0g,\s+ up to the last character before the last comma at the end of the line. if I do something like (my $value) = $_ ~= /,\s+(.*),\s+$/; The modifier * is greedy, but that is not your problem. Matches start searching at the left so ',\s+' will match the first comma-whitespace and then '(.*)' will match everthing except newline to the last ',\s+' comma-whitespace. The anchor is superfluous because '.*' is greedy. $value would start matching from pig because when I used $ and it looked back, the first thing it would match is , pig upto the end of the line I wonder how you could match only the pattern which is nearest to the end of the line having used $ anchor. To get around this, I could split the lines push each comma delimited string into an array and finally print the last element which is a lot of work to do. Is there some sort of turning of greedy behavior of the $ anchor? You could put a greedy match in front of your pattern: $ perl -le' my $string = boy, pig, 123, 123:412adbd, d0g, lajdlf134_ lkadsf !234,\n; my ( $value ) = $string =~ /.*,\s+(.*),\s+/; print $value; ' lajdlf134_ lkadsf !234 Or use split and return the last field: $ perl -le' my $string = boy, pig, 123, 123:412adbd, d0g, lajdlf134_ lkadsf !234,\n; my $value = ( split /,\s+/, $string )[ -1 ]; print $value; ' lajdlf134_ lkadsf !234 John -- Those people who think they know everything are a great annoyance to those of us who do.-- Isaac Asimov -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: Turn off $ anchor greedy behavior
Or use split and return the last field: $ perl -le' my $string = boy, pig, 123, 123:412adbd, d0g, lajdlf134_ lkadsf !234,\n; my $value = ( split /,\s+/, $string )[ -1 ]; Another mind bogling example... :-) I thought I would do: my @value = ( split /,\s+/, $string ); print $value[6]; How could your example, have printed the last field using [ -1 ]? Can I also print say, the 3rd field using this trick? print $value; ' lajdlf134_ lkadsf !234 John -- Those people who think they know everything are a great annoyance to those of us who do.-- Isaac Asimov -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/ -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: Turn off $ anchor greedy behavior
Aha, found it.. The split returned a list and you've just sliced it. giving [-1] means the list will start running through the elements backwards. --- On Tue, 4/14/09, Michael Alipio daem0n...@yahoo.com wrote: From: Michael Alipio daem0n...@yahoo.com Subject: Re: Turn off $ anchor greedy behavior To: Perl Beginners beginners@perl.org, John W. Krahn jwkr...@shaw.ca Date: Tuesday, April 14, 2009, 10:02 PM Or use split and return the last field: $ perl -le' my $string = boy, pig, 123, 123:412adbd, d0g, lajdlf134_ lkadsf !234,\n; my $value = ( split /,\s+/, $string )[ -1 ]; Another mind bogling example... :-) I thought I would do: my @value = ( split /,\s+/, $string ); print $value[6]; How could your example, have printed the last field using [ -1 ]? Can I also print say, the 3rd field using this trick? print $value; ' lajdlf134_ lkadsf !234 John -- Those people who think they know everything are a great annoyance to those of us who do.-- Isaac Asimov -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/ -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/ -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: Turn off $ anchor greedy behavior
On Tue, Apr 14, 2009 at 10:02, Michael Alipio daem0n...@yahoo.com wrote: Or use split and return the last field: $ perl -le' my $string = boy, pig, 123, 123:412adbd, d0g, lajdlf134_ lkadsf !234,\n; my $value = ( split /,\s+/, $string )[ -1 ]; Another mind bogling example... :-) I thought I would do: my @value = ( split /,\s+/, $string ); print $value[6]; snip That only works if you are certain you want the seventh item. If you always want the last item (regardless of how many items are in the array) you should say either print $value[$#value]; or print $value[-1]; Since you don't care about the other values it is probably better to index into the list than to store to a temporary array. -- Chas. Owens wonkden.net The most important skill a programmer can have is the ability to read. -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
