From: Christophe Rhodes <csr21@cantab.net>
Date: Fri, 7 Feb 2014 11:52:59 +0000 (+0000)
Subject: add one more "interesting" signum method
X-Git-Url: http://christophe.rhodes.io/gitweb/?p=paper-els-specializers.git;a=commitdiff_plain;h=ad5a5f9adaf1aa472f2cc563ae475577cca6089a

add one more "interesting" signum method
---

diff --git a/els-specializers.org b/els-specializers.org
index 9094ad2..b4e3e79 100644
--- a/els-specializers.org
+++ b/els-specializers.org
@@ -166,6 +166,12 @@
   (if (= (%signum s) (%signum g)) ; or EQL?
       (values t t)
       (values nil t)))
+
+;; this method is perhaps interesting enough to talk about?
+(defmethod specializer-accepts-generalizer-p ((gf signum-generic-function) (specializer sb-mop:specializer) (thing signum-specializer))
+  (specializer-accepts-generalizer-p gf specializer (class-of (%signum thing))))
+
+
 (defmethod specializer-accepts-p ((s signum-specializer) o)
   (and (realp o) (= (%signum s) (signum o))))
 
@@ -173,8 +179,8 @@
 
 (defgeneric fact (n)
   (:generic-function-class signum-generic-function))
-(defmethod fact ((n (signum 1))) (* n (fact (1- n))))
 (defmethod fact ((n (signum 0))) 1)
+(defmethod fact ((n (signum 1))) (* n (fact (1- n))))
 (defmethod fact ((n (signum -1)))
   (error "factorial of negative number: ~D" n))
 #+end_src