Re: without looping, check if $var is found in @list

It should be pointed out your example is, i believe; horrendously wrong. In:

 if ($var=~ m/@list/ ){ print 'ok'; }
[download]

What you are doing is attempting to match the @list inside of $var, and we know that $var does not hold all those things.

This would have worked:

#!/usr/bin/perl -w
use strict;
use warnings;

my @list = qw(frog turtle tadpole);
my $var = "turtle";

if ("@list" =~ /\b$var\b/) {
        print 'yup';
} # using quotes, we coerce the array to act as a string

else {
        print 'nope';
}
[download]

We didn't have to place the \b for this example to appear as if it worked. The \b means word boundary. Otherwise, we would match on 'turtles' and 'turtley'.

the idea is : $lookinside =~ /$for/

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Re^2: without looping, check if $var is found in @list by duckyd (Hermit) on Dec 15, 2006 at 02:32 UTC
Using string interpolation on the array is a bad idea - it won't neccessarily get you what you want. For example: `#!/usr/bin/perl -w use strict; use warnings; my @list = ('jumping turtle', 'frog', 'tadpole'); my $var = "turtle"; if ("@list" =~ /\b$var\b/) { print "yup\n"; }` [download] happily reports a match even though just "turtle" doesn't appear in the array, it's a "jumping turtle". I would be reluctant to assume that such behavior is desirable...	[reply] [d/l]
Re^2: without looping, check if $var is found in @list by ikegami (Patriarch) on Dec 15, 2006 at 04:49 UTC
It will fail (false positive or false negative) if `$var` contains regexp characters. `my $var = 'tad?pole'; my @list = ($var); print("@list" =~ /\b$var\b/ ? 1 : 0, "\n");` [download] It will fail (false negative) if `$var` starts or ends with `\W` (because `\b` won't match). `my $var = 'frog!'; my @list = ($var); print("@list" =~ /\b$var\b/ ? 1 : 0, "\n");` [download] It will fail (false positive or false negative) if `$var` contains spaces. (Credit goes to duckyd.) `my $var = 'turtle'; my @list = ("jumping $var"); print("@list" =~ /\b$var\b/ ? 1 : 0, "\n");` [download] If you knew a specific character will not be present in `@list`, you could use that character as a seperator. `my $sep = "\x01"; my @list = ('jumping turtle', 'frog!', 'tad?pole'); for my $var (@list) { if (join($sep, '', @list, '') =~ /\Q$sep$var$sep\E/) { print "Found $var\n" } else { print "Didn't find $var\n" } }` [download] You could even make it faster by using `index`. `my $sep = "\x01"; my @list = ('jumping turtle', 'frog!', 'tad?pole'); for my $var (@list) { if (index(join($sep, '', @list, ''), "$sep$var$sep") >= 0) { print "Found $var\n" } else { print "Didn't find $var\n" } }` [download] But really, are either of those solutions anywhere near as readable as those already suggested? That's without even taking into account the limitation of disallowing `$sep` from being in `@list`. Update: A few small corrections: Removed extra parens, fixed third snippet.	[reply] [d/l] [select]