Erlang has both methods, pattern matching in function definition and case-clause pattern matching.

(some random link http://stackoverflow.com/questions/1050913/erlang-style-case...)

In haskell you can write exactly the following:

    fact 0 = 0
    fact 1 = 1
    fact n = n * fact (n-1)

It works as you would expect and really they aren't that dissimilar.

Small correction, fact 0 = 1

Erlang does it very much like GP's suggestion with the one downside of being 'noisy' with its punctuation (some might say 'clearer'):

  factorial(0) -> 1;
  factorial(N) -> N * factorial(N-1).

  factorial(Foo, 0) -> .. ;
  factorial(Foo, Bar) -> .. .

Semicolons separate partial definitions for a single function of a single arity, and periods end those definitions. Removing the punctuation might make parsing a bit more difficult (will there be more partial definitions?), so it's understandable to not offer it.

Off-topic: I'm kinda new here, what does GP stand for ?

The grandparent comment, as opposed to the parent comment or the original post.

I'd imagine you could compile them both down to the same thing, as there has to be a conditional at some point to determine what code to run (unless there was some kind of dynamic dispatch), I think it's just a matter of preference