check if a value is in a given set

Ratazong has asked for the wisdom of the Perl Monks concerning the following question:

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Re: check if a value is in a given set by choroba (Cardinal) on Jul 24, 2012 at 15:34 UTC
I tend to use hashes if the set is larger, but I stay with `grep` if not and the test is not repeated much: `#!/usr/bin/perl use warnings; use strict; my @values = qw/banana plum apple strawberry pea/; my $var = 'apple'; my %hash; undef @hash{@values}; print exists $hash{$var} ? "yes\n" : "no\n"; print +(grep $_ eq $var, @values) ? "yes\n" : "no\n";` [download]	[reply] [d/l] [select]
Re: check if a value is in a given set by Anonymous Monk on Jul 24, 2012 at 15:33 UTC
Smart-matching seems to work OK. `use 5.010; my @set = qw/banana plum apple strawberry pear/; my $var = "apple"; if ($var ~~ @set) { say "yes"; }` [download] There are also hashes which might be a tad faster if your set is large. `my %set = map { $_ => 1 } qw/banana plum apple strawberry pear/; if (exists $set{$var}) { say "yes"; }` [download]	[reply] [d/l] [select]
Re: check if a value is in a given set by hippo (Archbishop) on Jul 24, 2012 at 16:21 UTC
It's an FAQ!	[reply]
Re: check if a value is in a given set by brx (Pilgrim) on Jul 24, 2012 at 15:40 UTC
Elegant? Hard to say... Smartmatch: `perl -e 'my @t=qw/banana plum apple strawberry pea/;my $fruit="apple"; +print (($fruit~~\@t)?"yes":"no");' yes` [download] Undef hash: `perl -e 'my @t=qw/banana plum apple strawberry pea/;my $fruit="apple"; +my %in;undef @in{@t};print ((exists $in{$fruit})?"yes":"no");' yes` [download] for,next,last: `perl -e 'my @t=qw/banana plum apple strawberry pea/;my $fruit="apple"; +for my $f (@t) {next if $fruit ne $f;print "yes";last}' yes` [download] grep? `#no, not efficient` [download] English is not my mother tongue. Les tongues de ma mère sont "made in France".	[reply] [d/l] [select]
Re: check if a value is in a given set by Marshall (Canon) on Jul 25, 2012 at 03:48 UTC
I want to check if a value is inside a set of predefined values. I would use grep. `#!/usr/bin/perl -w use strict; my @fruits = qw(banana plum apple strawberry pea); if ( grep {/apple/}@fruits ) #perhaps /^apple$/ { print "apple found!\n"; } else { print "apple not fouund\n"; } __END__ apple found!` [download] There are other ways see: List::Util	[reply] [d/l]
Re: check if a value is in a given set by 2teez (Vicar) on Jul 24, 2012 at 15:51 UTC
I will probably write this using List::Util like so: `#!/usr/bin/perl use warnings; use strict; use List::Util qw(first); my $var = 'apple'; my $h_ref = { banana => 1, plum => 1, apple => 1, strawberry => 1, pea => 1, }; my $foo = first { $_ eq $var } keys %{$h_ref}; defined $foo ? print "yes" : print "No";` [download] If your $var exist, it prints "Yes", if not you get a "No"	[reply] [d/l]
Re^2: check if a value is in a given set by Anonymous Monk on Jul 24, 2012 at 17:45 UTC
You have a set of hash keys, and enumerate through them to find whether the one you seek exists?	[reply]