Comparing Scalars and Arrays

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

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Re: Comparing Scalars and Arrays by btrott (Parson) on Jul 19, 2000 at 21:26 UTC
If you're going to do it more than once, use a hash. `my %hash; @hash{@array} = (); ## or @hash{@array} = (1) x @array; if (exists $hash{$scalar}) { ## Matched. }` [download] This is an FAQ. How can I tell whether a list or array contains a certain element?	[reply] [d/l]
Re: Comparing Scalars and Arrays by cwest (Friar) on Jul 19, 2000 at 21:27 UTC
Grep comes to mind... `y @array = ( 9, 2, 23, 24, 5, 6 ); my $scalar = 5; print "Got it\n" if grep /^$scalar$/, @array;` [download] also perlfaq4 should have this -- Casey	[reply] [d/l]
RE: Comparing Scalars and Arrays by autark (Friar) on Jul 19, 2000 at 21:31 UTC
If it smells like grep and looks like grep, then it must be grep :-) `if( grep { $scalar == $_ } @array ) { print "$scalar is member of @array\n"; } else { print "$scalar is not member of @array\n"; }` [download] I see that you in your question has assigned an anonymous array to @array, if that really is the case, then you have to do some more work: `$scalar = 3; @array = ([1, 2], [3, 4, 5], [6, 7, 8 ,9]); if( grep { $scalar == $_ } map { @$_ } @array ) { print "Yes\n" } else { print "No\n" }` [download] Autark.	[reply] [d/l] [select]
RE: RE: Comparing Scalars and Arrays by cwest (Friar) on Jul 19, 2000 at 21:36 UTC
IMHO, your second example is great, but the condition seems like it could be more readable. Since you use `grep`, why not use it again, instead of `map` `grep { grep { $scalar == $_ } @{$_} } @array` [download] Just MHO... Update:And it's faster, `1000000` iterations has Grep+Grep at 11 Walclocks and Grep+Map at 16. -- Casey	[reply] [d/l]
Re: Comparing Scalars and Arrays by lhoward (Vicar) on Jul 19, 2000 at 21:29 UTC
If this is a comparison you're goona do more than once then the best bet is to load the array into a hash as its keys and determine membership by looking for existance of the hash element. If this is something you need to do only once, then you're best off with something like this: `my $elem_count=grep /^$scalar$/,@array;` [download]	[reply] [d/l]
RE: Comparing Scalars and Arrays by Russ (Deacon) on Jul 19, 2000 at 22:38 UTC
Also see Categorized Q&A at How to find out if X is an element in an array? or here if the other link is broken. Russ Brainbench 'Most Valuable Professional' for Perl	[reply]