#!/usr/bin/perl -w
# (c) Declan Malone 2008
# Licensed under the terms of GPL 2 or later at your discretion
# Spurious info at project343.blogspot.com

sub quine {	   # agent for traversing a bi-coloured hexagonal space

  my $colouring_mod3=shift;	# ref to list of colours [0,1,2]
  my $colouring_mod7=shift;	# ref to list of colours [0,1,2,3,4,5,6]
  my $construction=shift;	# debug trail

  my ($t0,$t1,$t2)=@$colouring_mod3;
  my ($s0,$s1,$s2,$s3,$s4,$s5,$s6)=@$colouring_mod7;

  my $methods=
    {
     "STEP"  =>			# forward one step (0->1)
     sub {
       push @$construction, "STEP3 $t0 $t1";
       push @$construction, "STEP7 $s0 $s1";
       quine([$t1,$t2,$t0],[$s1,$s3,$s5,$s2,$s0,$s6,$s4],$construction);
     },
     "LEFT"  =>			# turn left 60 degrees
     sub {
       push @$construction, "LEFT";
       quine([$t0,$t2,$t1],[$s0,$s6,$s1,$s2,$s3,$s4,$s5],$construction);
     },
     "RIGHT"  =>		# turn right 60 degrees
     sub {
       push @$construction, "RIGHT";
       quine([$t0,$t2,$t1],[$s0,$s2,$s3,$s4,$s5,$s6,$s1],$construction);
     },
     "SELF" =>
     sub {
       push @$construction, "SELF";
       return ($t0,$s0);
     },
     "SELVES" =>
     sub {
       push @$construction, "SELVES";
       return ($colouring_mod3,$colouring_mod7);
     },
     "TRAIL" =>
     sub {
       $construction;
     }
    };
  return $methods;
}

my ($threes,$sevens);
my $trail=[];

$h=quine([0..2],[0..6],$trail);

print "I start at 0 in both three-coloured and seven-coloured space.\n";
print "The environment in the respective spaces are [0,1,2] and [0,1,2,3,4,5,6].\n";

$h=$h->{STEP}->();
$h=$h->{LEFT}->();
$h=$h->{STEP}->();
$h=$h->{RIGHT}->();
$h=$h->{STEP}->();

($three,$seven)=$h->{SELF}->();
($threes,$sevens)=$h->{SELVES}->();

#print "threes is $threes and its ref is ", ref($threes), "\n";
#print "sevens is $sevens and its ref is ", ref($sevens), "\n";

print "I am now at $threes->[0] in 3-space and $sevens->[0] in 7-space.\n";
print "I am now at $three in 3-space and $seven in 7-space.\n";
print "(the above two lines should print the same)\n";
print "The environment in 3-space is (", (join ",", @$threes), ")\n";
print "The environment in 7-space is (", (join ",", @$sevens), ")\n";
print "My tape reads:\n  ", (join "\n  ", @{$h->{TRAIL}->()}), "\n";