Data update

Task/Modular-arithmetic/Common-Lisp/modular-arithmetic-2.lisp

@@ -0,0 +1,25 @@
+(defpackage :rosetta-code/modular-arithmetic
+  (:use :cl))
+
+(in-package :rosetta-code/modular-arithmetic)
+
+(defparameter *modulus* nil)
+
+(defun make-modular (op)
+  (lambda (&rest args)
+    (let ((result (apply op args)))
+      (if *modulus*
+          (mod result *modulus*)
+          result))))
+
+(let ((ops '(+ expt))) ; add more operators as you need
+  (shadow ops)
+  (dolist (op ops)
+    (setf (symbol-function (find-symbol (symbol-name op)))
+          (make-modular (symbol-function (find-symbol (symbol-name op) :cl))))))
+
+(defun f (x)
+  (+ (expt x 100) x 1))
+
+(format t "No modulus: f(~a) = ~a~%" 10 (f 10))
+(format t "Modulus 13: f(~a) = ~a~%" 10 (let ((*modulus* 13)) (f 10)))