Data declaration with constraint
Revision as of 17:35, 21 December 2007 by Lemming
I have declared
and I hoped that now the type checker knows, that every value of type
data T a = C a => Cons a
satisfies the type constraint on
Only functions can have type constraints.The type constraint of a
only refers to the constructors.
The designers of Haskell 98 do now think, that it was a bad decision to allow constraints on constructors.
But how can one bake type constraints into a type ? ...