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raflach has asked for the wisdom of the Perl Monks concerning the following question:
What I want is something that will do "what I expect" of the following pseudo-code in perl
( $i in (1,2,3..9,-12) ) && do
{
print "$i is a 1, 2, 3, 4, 5, 6, 7, 8, 9, or -12\n";
}
I'm sure that I've seen this question covered before, but I couldn't find it--probably because I don't know the correct terminology to search for
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Re: looking for simple way to check scalar against array
by ikegami (Patriarch) on May 19, 2005 at 15:05 UTC
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And of course, the hash approach:
my %in;
undef @in{1, 2, 3..9, -12};
print "$i is a 1, 2, 3, 4, 5, 6, 7, 8, 9, or -12\n"
if exists $in{$i};
This method's advantage is that you can reuse the hash if you need to check if multiple variables are in the set, while still being extremely efficient.
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Re: looking for simple way to check scalar against array
by Joost (Canon) on May 19, 2005 at 14:53 UTC
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for (1,2,3..9,-12) {
if ($i == $_) {
print "$i is a 1, 2, 3, 4, 5, 6, 7, 8, 9, or -12\n";
last;
}
}
Shorter, but less efficient:
print "$i is a 1, 2, 3, 4, 5, 6, 7, 8, 9, or -12\n"
if grep { $_ == $i } (1,2,3..9,-12);
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Re: looking for simple way to check scalar against array
by reasonablekeith (Deacon) on May 19, 2005 at 15:13 UTC
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use strict;
use List::MoreUtils qw(any);
my @list = (1,2,3..9,-12);
my $i = -5;
print "$i is a " . join(',', @list) . "\n"
if any { $_ == $i } @list;
---
my name's not Keith, and I'm not reasonable.
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Re: looking for simple way to check scalar against array
by blazar (Canon) on May 19, 2005 at 14:55 UTC
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I like (and actually use)
sub is {
bless \shift, '_hidden';
}
sub _hidden::in {
my $s=${shift,};
$s eq $_ and return 1 for @_;
0;
}
use it thus:
do_something if is($item)->in(@list);
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Re: looking for simple way to check scalar against array
by Nevtlathiel (Friar) on May 19, 2005 at 14:54 UTC
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my @array = (1,2,3..9,-12);
foreach my $variable (@array) {
print "$variable is in the list\n";
}
That something like what you want?
Update: Oops, looks like I didn't really understand what you wanted, everyone else's suggestions are better :)
----------
My cow-orkers were talking in punctuation the other day. What disturbed me most was that I understood it.
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Re: looking for simple way to check scalar against array
by tcf03 (Deacon) on May 19, 2005 at 15:01 UTC
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#!/usr/bin/perl -w
use strict;
my $i = 4;
my @nums = ( 1 .. 9 );
push (@nums, -12);
for (@nums)
{
print if /$i/;
}
or
#!/usr/bin/perl -w
use strict;
my $i = 4;
for ( 1 .. 9, -12 )
{
print if /$i/;
}
UPDATE
What blazar ikegami and dug said.
My example was to show you what you might not want to do, but may or may not work anyway.
Ted
--
"That which we persist in doing becomes easier, not that the task itself has become easier, but that our ability to perform it has improved."
--Ralph Waldo Emerson
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Why use a regexp? It's inefficient, and that particular regexp will fail if 1) $i contains special characters, and 2) if $i is part of another number (e.g. when $i=1 and list=(2..10), your regexp will match).
print if /^\Q$i\E$/ would fix the problem.
print if $_ eq $i is equivalent, but much more efficient.
print if $_ == $i would be even more efficient given that we're dealing with numbers here.
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If the list contains anything with a 4 in it you will get a match, which I don't think is what the OP wants. If you are going to use the regex approach it should probably be anchored on both ends: /^$i$/.
update: Not that you really needed a third person to remind you [grin].
-- Douglas
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Gawd, believe me: I'm very keen on regexen myself, but I wouldn't use one where what you really want is an equality operator! And in that case it should be
/^$i$/ if you qw/really wanted to do it like that/;
Update: As duly pointed out by ikegami, to be really more precise, one should use /^\Q$i\E$/, which may seem nitpicking wrt this particular example, but which can be also absolutely necessary in other situations... (well, not that you would use this actual regex, but maybe a somewhat similar one.)
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