hi, it refers to type constructor. since value constructors are not allowed in the "instance head" the terminology is not ambiguous. on the other hand saying "type" would be wrong, as variables are (in a way) types, but they are not allowed there (in Haskell'98 that is). hope this helps iavor Ketil Malde wrote:
but got the following error in Hugs
ERROR "C:\zero.hs":5 - Syntax error in instance head (constructor expected)
I'm a bit puzzled by the terminology: What does "constructor" mean in this context? Normally, I'd use (unqualified) "constructor" to mean data constructor, as in Just, Nothing, Left, Right and so on.
(From the obvious Prelude stuff: data Maybe a = Just a | Nothing data Either a b = Left a | Right b )
Unless I'm completely confused, perhaps Hugs should expect a "type constructor" instead of just a "constructor" in its error message? Or perhaps it could simply say "type"?
-kzm
-- ================================================== | Iavor S. Diatchki, Ph.D. student | | Department of Computer Science and Engineering | | School of OGI at OHSU | | http://www.cse.ogi.edu/~diatchki | ==================================================