Both GHC and Hugs reject this module if the type signature for test is omitted. NHC (v1.00, 2000-09-15) falls over completely, with Fail: Prelude.chr: bad argument

Rushing to the defence of nhc98 (as always!), I should point out that nhc98 actually falls over here because of a bug in ghc. (I reported the bug several months ago.) If your nhc98 compiler was built by gcc, hbc, or nhc98 itself, then it gives a proper error message here, viz: Couldn't simplify the context ((_180#) _171). Possible sources for the problem are:11:20 However, this is totally unrelated to the question of interest regarding type inference. Regards, Malcolm