To air a contrarian view: Steve Yegge writes that Hindely-Milner languages lack the flexibility required to write good systems:
H-M is very pretty, in a totally
useless formal mathematical sense. It
handles a few computation constructs
very nicely; the pattern matching
dispatch found in Haskell, SML and
OCaml is particularly handy.
Unsurprisingly, it handles some other
common and highly desirable constructs
awkwardly at best, but they explain
those scenarios away by saying that
you're mistaken, you don't actually
want them. You know, things like, oh,
setting variables.
Haskell is worth learning, but it has its own weaknesses.
