Add compute-cpl tests

* test-suite/tests/goops.test: Add tests for compute-cpl based on
  comments from goops.scm.

* module/oop/goops.scm (compute-std-cpl): Remove comment, and add
  docstring.
  (compute-cpl): Improve comment.

module/oop/goops.scm

@@ -246,29 +246,8 @@
 (define (is-a? obj class)
   (and (memq class (class-precedence-list (class-of obj))) #t))
 
-
-;;; The standard class precedence list computation algorithm
-;;;
-;;; Correct behaviour:
-;;;
-;;; (define-class food ())
-;;; (define-class fruit (food))
-;;; (define-class spice (food))
-;;; (define-class apple (fruit))
-;;; (define-class cinnamon (spice))
-;;; (define-class pie (apple cinnamon))
-;;; => cpl (pie) = pie apple fruit cinnamon spice food object top
-;;;
-;;; (define-class d ())
-;;; (define-class e ())
-;;; (define-class f ())
-;;; (define-class b (d e))
-;;; (define-class c (e f))
-;;; (define-class a (b c))
-;;; => cpl (a) = a b d c e f object top
-;;;
-
 (define (compute-std-cpl c get-direct-supers)
+  "The standard class precedence list computation algorithm."
   (define (only-non-null lst)
     (filter (lambda (l) (not (null? l))) lst))
 
@@ -300,7 +279,8 @@
                                              c-direct-supers)
                                         (list c-direct-supers))))))
 
-;; Bootstrap version.
+;; This version of compute-cpl is replaced with a generic function once
+;; GOOPS has booted.
 (define (compute-cpl class)
   (compute-std-cpl class class-direct-supers))
 

test-suite/tests/goops.test

@@ -599,3 +599,26 @@
           (pass-if-equal 100 (slot-ref a 'test))
           (pass-if-equal 100 (slot-ref b 'test))
           (pass-if-equal 200 (slot-ref c 'test)))))))
+
+(define-class <food> ())
+(define-class <fruit> (<food>))
+(define-class <spice> (<food>))
+(define-class <apple> (<fruit>))
+(define-class <cinnamon> (<spice>))
+(define-class <pie> (<apple> <cinnamon>))
+
+(define-class <d> ())
+(define-class <e> ())
+(define-class <f> ())
+(define-class <b> (<d> <e>))
+(define-class <c> (<e> <f>))
+(define-class <a> (<b> <c>))
+
+(with-test-prefix "compute-cpl"
+  (pass-if-equal "<pie>"
+      (list <pie> <apple> <fruit> <cinnamon> <spice> <food> <object> <top>)
+    (compute-cpl <pie>))
+
+  (pass-if-equal "<a>"
+      (list <a> <b> <d> <c> <e> <f> <object> <top>)
+    (compute-cpl <a>)))