March 2014 update

Task/Modular-exponentiation/Scheme/modular-exponentiation.ss

@@ -0,0 +1,15 @@
+(define (square n)
+  (* n n))
+
+(define (mod-exp a n mod)
+  (cond ((= n 0) 1)
+        ((even? n)
+         (remainder (square (mod-exp a (/ n 2) mod))
+                    mod))
+        (else (remainder (* a (mod-exp a (- n 1) mod))
+                         mod))))
+
+(define result
+  (mod-exp 2988348162058574136915891421498819466320163312926952423791023078876139
+           2351399303373464486466122544523690094744975233415544072992656881240319
+           (expt 10 40)))