Add expression substitution for trig functions

larcs.org

@@ -606,6 +606,12 @@ Trigonemtric functions are also a bit weird -- as given a "normal" trig function
                  :initarg :expression
                  :type <expression>)))
 
+  (defmethod substitute-expression (replace replacement (expression <trig>))
+    (if (eqal expression replace)
+        replacement
+        (make-instance (type-of expression)
+                       :expression (substitute-expression replace replacement (slot-value expression 'expression)))))
+
   @export
   (defclass <inverse-trig> (<trig>) ())