Changeset 4376 for branches/f4grobner

Timestamp:

2016-06-06T19:53:00-07:00 (9 years ago)

Author:

Marek Rychlik

Message:

* empty log message *

File:

• branches/f4grobner/ring.lisp (modified) (2 diffs)

branches/f4grobner/ring.lisp

@@ -102 +102 @@
 should be returned upon every call."))
 
-(defun add (summand &rest more-summands)
+(defgeneric add (summand &rest more-summands)
   "Successively Adds to SUMMAND the elements of MORE-SUMMANDS. The first SUMMAND must not be destructively modified.
 Instead, a copy of factor should be made and returned as the value of
@@ -108 +108 @@
   (:method ((summand t) &rest more-summands)
     (reduce #'add-to more-summands :initial-value (copy-instance summand))))
+
+(defgeneric subtract (minuend  &rest subtrahends)
+  "Non-destructively subtract MINUEND and SUBTRAHENDS."
+  (:method ((minuend t) &rest subtrahends)
+    (cond ((endp subtrahends) (unary-minus (copy-instance minuend)))
+          (t (reduce #'subtract-from (copy-instance minuend) subtrahends)))))
 
 (defgeneric multiply (factor &rest more-factors)