Re: [Haskell-cafe] Type inference; always

On Sun, 2008-05-18 at 16:57 +0000, Luke Palmer wrote:

2008/5/18 Peter Verswyvelen :

...

In Haskell, I sometimes have to annotate code with type info because the type-inferer otherwise fails (even with -XNoMonomorphismRestriction). Surely, most of the time this is because I was writing buggy code, but sometimes, type annotation just seems needed to get a successful compilation (luckily not as often as in C# 3.0)

Then you must either be programming using extensions or you have found a bug. Haskell 98 should never require annotations (modulo monomorphism).

This is incorrect. There are two (other) situations where you need type annotations in Haskell 98. One situation is when you use polymorphic recursion, but that is pretty rare unless you are writing nested data types. The other situation is when not enough information is provided to resolve a typeclass constraint, e.g. good ole show . read.