hipeta / metap

Metap provides metaclass propagation along class inheritance structure in Common Lisp

Metap

Metap provides metaclass propagation along class inheritance structure. Metap uses closer-mop and changes

• c2mop:ensure-class-using-class :around class name &rest args

so it could conflicts with other library modifing same method.

Motivation

You got some idea which use metaclass like

(defclass some-meta-class (standard-class) ())
(defmethod something1 ((class some-meta-class) ...) ...)
(defmethod something2 ((class some-meta-class) ...) ...)

and use this for some classes like

(defclass some-class1 () () (:metaclass 'some-meta-class))
(defclass some-class2 (some-class1) () (:metaclass 'some-meta-class))
(defclass some-class3 (some-class2) () (:metaclass 'some-meta-class))
(defclass some-class4 (some-class1) () (:metaclass 'some-meta-class))
... :metaclass :metaclass :metaclass :metaclass

This is boring. Using metap, it can simply be written like

(defclass some-mixin () ())
(metap:register-m1-m2-pair 'some-mixin 'some-meta-class)

(defclass some-class1 (some-mixin) ())
(defclass some-class2 (some-class1) ())
(defclass some-class3 (some-class2) ())
(defclass some-class4 (some-class1) ())

Also see cl-singleton-mixin (https://github.com/hipeta/cl-singleton-mixin) which is written by using metap.

APIs

Variables

• *metap-m1-m2-pairs*

• All pairs registered in metap.

Functions

• register-m1-m2-pair (m1class m2class)

• Register m1class and m2class pair which you want to enable metaclass propagation.

Macros

• validate-superclass* (&body validations)

• Syntax sugar for c2mop:validate-superclass.

Installation

(ql:quickload :metap)

License

Metap is released under the MIT License, see LICENSE file.

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