Re: Logical operations on arrays

[MidLifeXis]

If the order of the arrays makes no difference, it sounds like you are looking for an intersection operator of some sort. Array::Utils might have what you are looking for. I found this by searching metacpan for "union intersect".

Otherwise, a method to find them is pretty straightforward:

• configure a hash for the first array (*)

  @hash1{@array1} = (1)x@array1
  

  This configures a hash %hash1 to have a true value for all values found in @array1. (* - This is probably clearer as $hash1{$_} = 1 for @array1)
• loop through the second array picking out those elements that show up in the first array

  push( @intersection, grep { $hash1{$_} } @array2 );
  

There are a couple of assumptions built into the above (@arrayN does not contain an undef value, and the second array only has unique values).

Updates:

1. Added example code
2. Added search example
3. D'oh - quite right Jenda. I have got to stop writing code before my first cup of coffee. :-/

[Athanasius]

See also How do I compute the difference of two arrays? How do I compute the intersection of two arrays?.

[Jenda]

There's no reason to work hard to set the values in the hash to ones, leave them undefined and use exists() within the grep{}. Also there is no reason to push the elements into the @intersection, just assign them.

my %hash1;
@hash1{@array1} = ();
my @intersection = grep {exists $hash1{$_} } @array2;