> Date: Sun, 13 Jun 1999 01:51:06 -0400
> From: Kevin Atkinson <[EMAIL PROTECTED]>
> Could some one explain to me why [this is not OK]:
> class T f r
>
> instance T a (d a)
> instance T (c a b) (c a (d b))
Because, just as Hugs says:
> *** Common instance : T (a b c) (a b (a b c))
given
data Foo a b = Foo a b
the type
T (Foo Int Char) (Foo Int (Foo Int Char))
will match both instance declarations --- the first one with
a = (Foo Int Char)
d = (Foo Int)
the second one with
c = Foo
a = Int
b = Char
d = (Foo Int)
Lars Mathiesen (U of Copenhagen CS Dep) <[EMAIL PROTECTED]> (Humour NOT marked)
