examples/hq9+.pl

   1 class HQ9Plus;
   2
   3 # 2006-12-19 (rough) update to current spec
   4
   5 my subset HQ9PlusProgram
   6     of Str
   7     where /^ <[hq9+]>* $/;
   8
   9 my subset HQ9PlusStep
  10     of HQ9PlusProgram
  11     where { .chars == 1 };
  12
  13 my subset Error::OutOfBounds of Failure where True;
  14
  15 has HQ9PlusProgram $.program;
  16 has Int            $.accumulator = 0;
  17 has Int            $position = 0; # twigilless are private
  18
  19 has %actions = (
  20     'h' => { self.hello },
  21     'q' => { self.quine },
  22     '9' => { self.nine  },
  23     '+' => { self.plus  },
  24 );
  25
  26 method run () {
  27     # Java, anyone? Feel free to fix this.
  28     loop {
  29         .step;
  30         CATCH {
  31             when Error::OutOfBounds {
  32                 return; # end of program
  33             }
  34             default { fail }
  35         }
  36     }
  37 }
  38
  39 method step () {
  40     given $.program.substr($position++, 1) {
  41         %actions{$_}();
  42     }
  43 }
  44
  45 my method hello () { say "Hello, world!" }
  46 my method quine () { say $.program }
  47 my method plus  () { $.accumulator++ }
  48 my method nine  () {
  49     my Int $i = 99;
  50
  51     while $i {
  52         say qq:to/END/;
  53             $i bottles of beer on the wall
  54             $i bottles of beer!
  55             Take one down, pass it around
  56             END
  57         $i--;
  58         say "$i bottles of beer on the wall!"
  59     }
  60 }
  61
  62 =begin END
  63 =head1 NAME
  64
  65 HQ9Plus - A HQ9+ implementation
  66
  67 =head1 SYNOPSIS
  68
  69     HQ9Plus.new(program => $foo).run;
  70
  71     my $program = HQ9Plus.new(program => $foo);
  72
  73     while ... {
  74         $program.step;
  75         ...inspect the program state...
  76     }
  77
  78 =head1 DESCRIPTION
  79
  80 C<HQ9Plus> implements a I<HQ9+> interpreter with stepping.
  81
  82 =head1 SEE ALSO
  83
  84 http://en.wikipedia.org/wiki/HQ9+
  85
  86 =head1 AUTHOR
  87
  88 Ilmari Vacklin <ilmari.vacklin@helsinki.fi>
  89
  90 =head1 LICENSE
  91
  92 Public domain.