Data commit

Task/Modular-arithmetic/Common-Lisp/modular-arithmetic.lisp

@@ -0,0 +1,24 @@
+(defvar *modulus* nil)
+
+(defmacro define-enhanced-op (enhanced-op op)
+  `(defun ,enhanced-op (&rest args)
+     (if *modulus*
+         (mod (apply ,op args) *modulus*)
+         (apply ,op args))))
+
+(define-enhanced-op enhanced+ #'+)
+(define-enhanced-op enhanced-expt #'expt)
+
+(defun f (x)
+  (enhanced+ (enhanced-expt x 100) x 1))
+
+;; Use f on regular integers.
+(princ "No modulus:  ")
+(princ (f 10))
+(terpri)
+
+;; Use f on modular integers.
+(let ((*modulus* 13))
+  (princ "modulus 13:  ")
+  (princ (f 10))
+  (terpri))