X-Git-Url: https://git.distorted.org.uk/~mdw/sod/blobdiff_plain/f64eb323a5798e155cc494043f5f750abf50a482..f458e64e36509fa8c204f1dbcafff1d3dc059619:/src/class-make-proto.lisp

diff --git a/src/class-make-proto.lisp b/src/class-make-proto.lisp
index d075304..2e1fe7c 100644
--- a/src/class-make-proto.lisp
+++ b/src/class-make-proto.lisp
@@ -28,6 +28,14 @@
 ;;;--------------------------------------------------------------------------
 ;;; Classes.
 
+(export 'guess-metaclass)
+(defgeneric guess-metaclass (class)
+  (:documentation
+   "Determine a suitable metaclass for the CLASS.
+
+   The default behaviour is to choose the most specific metaclass of any of
+   the direct superclasses of CLASS, or to signal an error if that failed."))
+
 (export 'make-sod-class)
 (defun make-sod-class (name superclasses pset &optional location)
   "Construct and return a new SOD class with the given NAME and SUPERCLASSES.
@@ -46,12 +54,13 @@
   (with-default-error-location (location)
     (let* ((pset (property-set pset))
 	   (best-class (or (get-property pset :lisp-metaclass :symbol nil)
-			   (if superclasses
-			       (maximum (mapcar #'class-of superclasses)
-					#'subtypep
-					(format nil "Lisp metaclass for ~A"
-						name))
-			       'sod-class)))
+			   (select-minimal-class-property
+			    superclasses #'class-of #'subtypep 'sod-class
+			    "Lisp metaclass"
+			    :present (lambda (class)
+				       (format nil "`~S'"
+					       (class-name class)))
+			    :allow-empty t)))
 	   (class (make-instance best-class
 				 :name name
 				 :superclasses superclasses