Keyword arguments

[toivoh]

Once #10 is in place, it might be worth to try to construct a mechanism for keyword arguments on top of it. In it's simplest form, this could be dict parameters with a way to supply default values.

It might also be possible to embed this more firmly into the syntax, e.g.

@pattern f(:x => x::Int, :y => y::Int) = ...

Such a function might be called in a way like (@p f(:x => 5, :y => 2)). This kind of integration would hopefully be able to decrease overhead as well, circumventing actual construction and inspection of dicts.