Acme::IEnumerable, lazy generators for Perl.

gistfile1.pl

package main;
use Modern::Perl;
use Coro::Generator;

my $even = generator {
  my $x = 0;
  while(1) {
    $x += 2;
    # use references as boxing mechanism
    # yield non-reference to indicate end
    yield \$x;
  }
};

my $enum = Acme::IEnumerable->from($even);

# prints 2 4 6
say for $even->where(sub { $_ > 5 })
             ->take(3)
             ->to_list;

package Acme::IEnumerable;
use strict;
use warnings;
use Coro::Generator;

sub to_list {
  my ($enum) = @_;
  my @list;
  while (1) {
    my $item = $enum->();
    last unless ref $item;
    push @list, $$item;
  }
  @list;
}

sub take {
  my ($enum, $count) = @_;
  my $self = generator {
    for (0 .. $count - 1) {
      my $item = $enum->();
      yield $item;
    }
    yield undef while 1;
  };
  bless $self, ref $enum;
}

sub where {
  my ($enum, $filter) = @_;
  my $self = generator {
    while (1) {
      my $item = $enum->();
      local $_ = $item;
      next unless $filter->($item);
      yield $item;
    }
  };
  bless $self, ref $enum;
}

sub from {
  my $class = shift;
  my $from = shift;
  bless $from, $class;
}