Re: Array indices

[jkahn]

Your indices function sounds sorta like the smart match code that I heard theDamian talk about at his Perl6 talk -- well, at least knowing whether "heimer" is in the list.

Of course, you could write your own indices() function pretty quickly, using a sort of modification of the Schwartzian Transform (I actually have tested this, on a few cases, but let me know if I've missed anything):

sub indices ($@) {
  # note the prototype has target, then list
  my $target = shift;
  my (@list) = @_;

  my $index = 0;
  map { $_->[1] }
    grep { $_->[0] eq $target }
      map { [$_ , $index++] } @list;
}

I'm sure some wizard out there could tighten this up, but I think it's pretty clear what I'm aiming at.

[Aristotle]

I wouldn't use a prototype here. They're much more headache than they're usually worth.

sub indices {
    my $match = shift;

    my $i = 0;
    map { $i++; $_ eq $match ? $i : () } @_
}

Returning an empty list in the map callback causes that iteration to disappear from the result list. This is useful because you can use it as a surrogate grep that allows you to return something other than what your input was.

Update: removed ->[0] copy paste remainder from code.

Update 2: the following is more idiomatic and pretty much makes having a separate sub useless. We're back to grep too:

sub indices {
    my $match = shift;
    grep $_[$_] eq $match, 0 .. $#_
}

Makeshifts last the longest.