check if a number is in a list

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

Replies are listed 'Best First'.
Re: check if a number is in a list by crashtest (Curate) on Jun 26, 2005 at 02:36 UTC
You almost got it. Use "==" (not "=") for number comparisons: `if (grep $_ == $x, @array) { print "Found $x in the array!\n"; }` [download] ... or, if you like the regular expression, just anchor it: `if (grep /^$x$/, @array){ ... }` [download]	[reply] [d/l] [select]
Re: check if a number is in a list by runrig (Abbot) on Jun 26, 2005 at 02:38 UTC
You want '==' there. You might want to store the values as keys in a hash though (update: as davidrw demonstrates below -- do it that way if you're doing many checks on the same list) to make it simple, or do something like: `my @array = qw(1 2 3); my $x = 1; if (num_in($x, @array)) { ... } sub num_in { my $num = shift; $_ == $num and return 1 for @_; return; }` [download]	[reply] [d/l]
Re^2: check if a number is in a list by davidrw (Prior) on Jun 26, 2005 at 03:12 UTC
(for OP's benefit) the hash method: `my @array = (10,11,12,13,14,20,21,25); my $x = 1; my %array = map { $_ => undef } @array; if( exists $array{$x} ){ ... }` [download]	[reply] [d/l]
Re^3: check if a number is in a list by Ido (Hermit) on Jun 26, 2005 at 05:21 UTC
Is the map really needed? What about: `my %array; @array{@array}=();` [download]	[reply] [d/l]
Re^3: check if a number is in a list by 5mi11er (Deacon) on Jun 27, 2005 at 16:33 UTC
No, the map isn't really needed, and might cause confusion, but if it does, I'd bet the @array{@array}=(); idiom isn't going to be understood either. OP, in both cases above, the idea is to have the numbers in your list to actually be in a hash rather than an array. The map and @array{@array} thing are simply shorthand ways to take your existing array and make it into a hash. Depending on your actual implementation, you might be better off if you created and added/removed the numbers meant to be within the list, and did so using hash operations instead. Then you wouldn't need the shorthand idioms above. -Scott	[reply]
Re: check if a number is in a list by neniro (Priest) on Jun 26, 2005 at 10:00 UTC
You can also use Perl6::Junction for a more "natural" way: `use Perl6::Junction qw/any/; if (any(@list_of_values) == $value) { ... }` [download]	[reply] [d/l]