adding in the Y combinator stuff

[gitmo/Moose-Autobox.git] / lib / Moose / Autobox / Code.pm

diff --git a/lib/Moose/Autobox/Code.pm b/lib/Moose/Autobox/Code.pm
index 8902d72..e19ee54 100644 (file)
--- a/lib/Moose/Autobox/Code.pm
+++ b/lib/Moose/Autobox/Code.pm
@@ -1,8 +1,8 @@
 package Moose::Autobox::Code;
 use Moose::Role 'with';
-use autobox;
+use Moose::Autobox;
 
-our $VERSION = '0.01';
+our $VERSION = '0.02';
 
 with 'Moose::Autobox::Ref';
 
@@ -32,6 +32,16 @@ sub conjoin {
        return sub { $f->(@_) && $f2->(@_) }    
 }
 
+sub u {
+    my $f = shift;
+    sub { $f->($f, @_) };
+}
+
+sub y {
+    my $f = shift;
+    (sub { my $h = shift; sub { $f->(($h->u())->())->(@_) } }->u())->();
+}
+
 #sub dump {
     #my ($self) = @_;
     #require Data::Dump::Streamer;
@@ -51,12 +61,25 @@ Moose::Autobox::Code - the Code role
 =head1 SYNOPOSIS
 
   use Moose::Autobox;
-  use autobox;
   
   my $adder = sub { $_[0] + $_[1] };
   my $add_2 = $adder->curry(2);
   
   $add_2->(2); # returns 4
+  
+  # create a recursive subroutine 
+  # using the Y combinator
+  *factorial = sub {
+      my $f = shift;
+      sub {
+          my $n = shift;
+          return 1 if $n < 2;
+          return $n * $f->($n - 1);
+      }
+  }->y;
+  
+  factorial(10) # returns 3628800
+  
 
 =head1 DESCRIPTION
 
@@ -79,6 +102,14 @@ This is a role to describe operations on the Code type.
 This will take a list of C<@subs> and compose them all into a single 
 subroutine where the output of one sub will be the input of another. 
 
+=item B<y>
+
+This implements the Y combinator.
+
+=item B<u>
+
+This implements the U combinator.
+
 =back
 
 =over 4
@@ -87,6 +118,14 @@ subroutine where the output of one sub will be the input of another.
 
 =back
 
+=head1 SEE ALSO
+
+=over 4
+
+=item L<http://en.wikipedia.org/wiki/Fixed_point_combinator>
+
+=back
+
 =head1 BUGS
 
 All complex software has bugs lurking in it, and this module is no 
@@ -106,4 +145,4 @@ L<http://www.iinteractive.com>
 This library is free software; you can redistribute it and/or modify
 it under the same terms as Perl itself.
 
-=cut
\ No newline at end of file
+=cut