Macros for programming in type-class-style in Scheme.
Andre Van Tonder. Ported to Chicken by Ivan Raikov.
- (define-class NAME FIELD-FORM ...) syntax
Defines a type class named NAME, where FIELD-FORM ... defines one or more fields for instances of this class. FIELD-FORM should be of the form:
FIELD-FORM = FIELD-LABEL | (SUPERCLASS-NAME FIELD-LABEL)
SUPERCLASS-NAME is the name of a class from which the field is inherited.
The result of this macro is the creation of a constructor with name of the form MAKE-CLASSNAME, which in turn takes an instance constructor procedure and applies to the given field values.
- (define=> (<PROCEDURE-NAME> <CLASS-FORM> ...) . BODY) syntax
Defines a procedure such that all fields of the given class(es) are visible in the scope of the procedure body.
CLASS-FORM is of the following form:
CLASS-FORM = CLASS-NAME | (CLASS-NAME PREFIX-SYMBOL)
- (lambda=> (<CLASS-FORM> ...) . BODY) syntax
Anonymous procedure such that all fields in the superclasses of the given class are visible in the scope of the procedure body.
- (with-instance (<INSTANCE-FORM> ...) . BODY) syntax
An expression such that all fields of the given class(es) are visible in the scope of BODY.
INSTANCE-FORM is of the following form:
INSTANCE-FORM = (CLASS-NAME INSTANCE-EXPR) | (CLASS-NAME INSTANCE-EXPR PREFIX-SYMBOL)
- (import-instance <INSTANCE-FORM> ...) syntax
Imports all fields of the given classes as identifiers in the current scope.
;======================================================= ; Equality example: ; class (Eq a) where ; egal? : a a -> boolean ; not-egal? : a a -> boolean (define-class <Eq> egal? not-egal?) (define (default-Eq egal?) (make-<Eq> egal? (lambda (x y) (not (egal? x y))))) (define num-Eq (default-Eq =)) (define eqv-Eq (default-Eq eqv?)) (define chr-Eq (default-Eq char=?))
- 1.0 Initial Release
Copyright (c) 2004-2010, Andre van Tonder, Ivan Raikov.
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