Re: counting overlapping patterns

[Eimi Metamorphoumai]

The key is to match without consuming text. The following works.

while("AAAA" =~ /(?=AA)/g){
  $count++;
}

It'll go through it repeatedly, starting at each position, but never consuming anything.

[ikegami]

Alternatively,

while ('AAAA' =~ /A(?=A)/g) {
   $count++;
}

which looks slightly less weird to me.

[Eimi Metamorphoumai]

But requires rewriting the pattern. Mine will work even if the pattern comes from a variable, or contains different possibilities for the first character ('/AA|BB/' becomes '/(?=AA|BB)/'). My approach was to try to do minimal tinkering with the original, but yeah, it's not as obvious what's actually going on.

[ikegami]

Good point.