From: Jan Moringen <jmoringe@techfak.uni-bielefeld.de>
Date: Sat, 17 May 2014 21:56:56 +0000 (+0200)
Subject: added PCL hot-patch with MAKE-SPECIALIZER-FORM-USING-CLASS
X-Git-Url: http://christophe.rhodes.io/gitweb/?p=specializable.git;a=commitdiff_plain;h=24d498e3131111f61bb5f4a2cf167d9ab859774f

added PCL hot-patch with MAKE-SPECIALIZER-FORM-USING-CLASS
---

diff --git a/src/pcl-patch.lisp b/src/pcl-patch.lisp
index 6f61974..e78457b 100644
--- a/src/pcl-patch.lisp
+++ b/src/pcl-patch.lisp
@@ -73,3 +73,90 @@ return three values:
                                        (class-name (class-of proto-method))
                                        'standard-method)
                                    initargs-form)))))))
+
+;;; `make-specializer-form-using-class'
+;;;
+;;; To free every new custom generic function class from having to
+;;; implement iteration over specializers in
+;;; `make-method-specializers-form', we provide a default method
+;;;
+;;;   make-method-specializers-form standard-g-f standard-method
+;;;
+;;; which performs this iteration and calls the generic function
+;;;
+;;;   make-specializer-form-using-class proto-g-f proto-m specializer-names env
+;;;
+;;; on which custom generic function classes can install methods to
+;;; handle their custom specializers. The generic function uses OR
+;;; method combination to allow the following idiom:
+;;;
+;;;   (defmethod make-specializer-form-using-class or
+;;;       (proto-generic-function MY-GENERIC-FUNCTION)
+;;;       (proto-method standard-method)
+;;;       (specializer-name cons)
+;;;       (environment t))
+;;;     (when (typep specializer-name '(cons (eql MY-SPECIALIZER)))
+;;;       MY-SPECIALIZER-FORM))
+;;;
+;;; The OR method combination lets everything but (my-specializer …)
+;;; fall through to the next methods which will, at some point, handle
+;;; class and eql specializers and eventually reach an error signaling
+;;; method for invalid specializers.
+
+(defmethod make-method-specializers-form
+    ((proto-generic-function standard-generic-function)
+     (proto-method standard-method)
+     (specializer-names t)
+     (environment t))
+  (flet ((make-parse-form (name)
+           (make-specializer-form-using-class
+            proto-generic-function proto-method name environment)))
+    `(list ,@(mapcar #'make-parse-form specializer-names))))
+
+;; TODO same approach for parse-specializer-using-class?
+(defgeneric make-specializer-form-using-class (proto-generic-function proto-method specializer-name environment)
+  (:method-combination or)
+  #+sb-doc
+  (:documentation
+   "Return a form which, when evaluated in lexical environment
+    ENVIRONMENT, parses the specializer SPECIALIZER-NAME and returns
+    the appropriate specializer object.
+
+    Both PROTO-GENERIC-FUNCTION and PROTO-METHOD may be
+    uninitialized. However their types and prototype can be
+    inspected."))
+
+;; Default behavior is signaling an error for not otherwise handled
+;; specializers.
+(defmethod make-specializer-form-using-class or
+    ((proto-generic-function standard-generic-function)
+     (proto-method standard-method)
+     (specializer-name t)
+     (environment t))
+  (error 'simple-reference-error
+         :format-control
+         "~@<~S is not a valid parameter specializer name.~@:>"
+         :format-arguments (list specializer-name)
+         :references (list '(:ansi-cl :macro defmethod)
+                           '(:ansi-cl :glossary "parameter specializer name"))))
+
+(defmethod make-specializer-form-using-class or
+    ((proto-generic-function standard-generic-function)
+     (proto-method standard-method)
+     (specializer-name symbol)
+     (environment t))
+  `(find-class ',specializer-name))
+
+(defmethod make-specializer-form-using-class or
+    ((proto-generic-function standard-generic-function)
+     (proto-method standard-method)
+     (specializer-name cons)
+     (environment t))
+  ;; In case of unknown specializer or known specializer with syntax
+  ;; error, TYPECASE may fall through to default method with error
+  ;; signaling.
+  (typecase specializer-name
+    ((cons (eql eql) (cons t null))
+     `(intern-eql-specializer ,(second specializer-name)))
+    ((cons (eql class-eq) (cons t null))
+     `(class-eq-specializer (find-class ',(second specializer-name))))))