3.11 Typeclass

This library defines some macros that provide ad-hoc polymorphism similar to typeclasses, although lacking some of the crucial features of typeclasses such as typeclass constraints. These typeclasses are added entirely through meta-programming.

syntax
( typeclass (class(param:Type))(name:t)...)

Declares a new typeclass named class, whose parameter param has type Type. Implementations of this typeclass must define of the methods name... whose types are t....

Example:

> (typeclass (Eqv(A:Type))
(equal?:(->(a:A)(b:A)Bool )))

syntax
( impl (classparam)defs...)

Provides an implementation of the typeclass class for the type param. The defintions defs... are Cur definitions for each of the methods of the typeclass.

Examples:

> (impl (EqvBool )
(define(equal?(a:Bool )(b:Bool ))
(if a
(if btrue false )
(if bfalse true ))))

> (impl (EqvNat )
(defineequal?nat-equal? ))
> (equal?true true )

(true)
> (equal?z z )

(true)

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