And now one for those who say Perl 6 isn't the coolest thing since sliced bread. I've been reading the Perl blogosphere, and found a couple of posts that show off some what happens when you convert an advanced Perl 5 program into Perl 6. The results are definitely amazing.
Here is the Perl 5 version:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 | #!/usr/bin/perl use strict; use warnings; my $op_dispatch_table = { '+' => sub { my ($stack) = @_; push @$stack, pop(@$stack) + pop(@$stack); }, '-' => sub { my ($stack) = @_; my $s = pop(@$stack); push @$stack, pop(@$stack) - $s; }, '*' => sub { my ($stack) = @_; push @$stack, pop(@$stack) * pop(@$stack); }, '/' => sub { my ($stack) = @_; my $s = pop(@$stack); push @$stack, pop(@$stack) / $s; }, 'sqrt' => sub { my $stack = shift; push @$stack, sqrt(pop(@$stack)); }, }; my $result = evaluate($op_dispatch_table, $ARGV[0]); print "Result: $result\n"; sub evaluate { my $odt = shift; my @stack; my ($expr) = @_; my @tokens = split /\s+/, $expr; for my $token (@tokens) { if ($token =~ /\d+$/) { push @stack, $token; } else { if (my $fn = $odt->{$token}) { $fn->(\@stack); } else { die "Unrecognized token '$token'; aborting"; } } } return pop(@stack); } |
And here is the fully optmized Perl 6 version:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | my %op_dispatch_table = { '+' => { .push(.pop + .pop) }, '-' => { .push(.pop R- .pop) }, '*' => { .push(.pop * .pop) }, '/' => { .push(.pop R/ .pop) }, 'sqrt' => { .push(.pop.sqrt) }, }; sub evaluate (%odt, $expr) { my @stack; my @tokens = $expr.split(/\s+/); for @tokens { when /\d+/ { @stack.push($_); } when ?%odt{$_} { %odt{$_}(@stack); } default { die "Unrecognized token '$_'; aborting"; } } @stack.pop; } say "Result: { evaluate(%op_dispatch_table, @*ARGS[0]) }"; |
Quite a difference eh? Anyway, I'd recommend reading the original post by fREW Schmidt, the reply and optimization post by pmichaud, and the follow up post by fREW.
Perl 6 might not solve world hunger, but it is the coolest thing since sliced bread.