So I have been hanging out at #perl6 and working with autrijus and the group on PUGS. Mostly I have been writing tests, but recently I decided to whip up some code examples to test my new found perl 6 knowledge.

Now I have always been a fan of functional languages, and one of my favorite features of functional languages is argument pattern matching. So I decided to try and reproduce some of the classic examples of argument pattern matching using the multi-sub feature of perl 6.

Here is the Standard ML code I based these examples off of. 

fun sum [ ] = 0
  | sum (h::t) = h + (sum t);

fun length [ ] = 0
  | length (h::t) = 1 + (length t);

[download]
And the Perl 6 code ... 
multi sub sum ()          returns Int { 0             }
multi sub sum (*$x, *@xs) returns Int { $x + sum(@xs) }

multi sub length ()          returns Int { 0               }
multi sub length (*$x, *@xs) returns Int { 1 + length(@xs) }

[download]
And the equivalent (sorta) Perl 5 code ... 
sub sum {
    return 0 unless @_;
    my ($h, @t) = @_;
    return $h + sum(@t);
}

sub length {
    return 0 unless @_;
    shift;
    return 1 + length(@_);
}

[download]
These examples are quite simple, but the full example code has a few more complex examples in it.

I encourage anyone who is doubting the future of perl 6 to download the latest PUGS and give it a try. Even though it is still a little rough around the edges, it is progressing quite nicely and has a number of new and interesting language features already implemented.

And of course we can always use more tests and examples.

-stvn

In reply to Functional Perl 6/PUGS by stvn

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