How to make this work?
Trying to understand how classes must be used:
signature MY_ORD = sig
class strict_less
val lt : t ::: Type -> strict_less t -> t -> t -> bool
val le : t ::: Type -> strict_less t -> t -> t -> bool
end
structure My_Ord : MY_ORD = struct
class strict_less a = a -> a -> bool
fun lt [a] (f: strict_less a) (x:a) (y:a) = f x y
(* causing Can't resolve type class instance
Class constraint: Basis.eq a
*)
fun le [a] (f: strict_less a) (x:a) (y:a) = f x y || x = y
end
The le implementation does not know which eq implementation to use ?
Is using functor the way to go?
I can't trivially apply the max sample from:
http://www.impredicative.com/ur/tutorial/intro.html
Marc Weber
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