7 May
2010
7 May
'10
8:15 p.m.
On Sat, May 08, 2010 at 01:54:21AM +0200, Limestraël wrote:
Personally I think fail is a terrible wart, and should be shunned.
So do I. I can't understand its purpose since monads which can fail can be implemented through MonadPlus.
It was introduced to implement pattern match failure in do-notation, in Section 3.14 of the Haskell Report: do {p <- e; stmts} = let ok p = do {stmts} ok _ = fail "..." in e >>= ok