#!/usr/bin/perl -w
#
# create and test a "map2" function that behaves similar to the
# built-in "map" function, but takes two lists instead of just one as
# input.
#
# abigail wrote one that is much snazzier, but i can't find her web
# page right now.
#
# similar to how "sort" takes its arguments, the block here should use
# $a and $b for the two elements.  the block is called in list
# context, just as in the "real" map.

use strict;
use vars qw($a $b);

sub map2 (&\@\@) 
{
  my ($code_ref, $a_ref, $b_ref) = @_; 
  my $max_index = (@$a_ref < @$b_ref) ? @$a_ref : @$b_ref;
  my @rv;
  local ($a, $b);
  for (my $i = 0; $i < $max_index; ++$i)
  {
    ($a, $b) = ($a_ref->[$i], $b_ref->[$i]);
    push @rv, &$code_ref;
  } 
  return @rv; 
}

my @a        = (1, 2, 3);
my @b        = (4, 9, 1);
my @sum      = map2 { $a+$b } @a, @b;
my @product  = map2 { $a*$b } @a, @b;

$" = ", ";
print 
  "a=(@a)\n",
  "b=(@b)\n",
  "sum=(@sum)\n",
  "product=(@product)\n";

exit;