functor

Frank Atanassow [email protected]
Tue, 30 Oct 2001 09:34:26 +0100


Wolfgang Jeltsch wrote (on 29-10-01 23:43 +0100):
> you cannot use sections with types and (->). Furthermore the variable must 
> begin with a lowercase letter. So you have to write
>     instance Functor (->) a where.

Erp, I said that the Functor class has arity *. Actually, it has arity 1
(i.e., it is a unary relation on types), with the argument being of kind
*->*. This is one of the infelicities of the class system.

-- 
Frank Atanassow, Information & Computing Sciences, Utrecht University
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