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Task/Modular-exponentiation/EchoLisp/modular-exponentiation.echolisp

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+(lib 'bigint)
+
+(define a 2988348162058574136915891421498819466320163312926952423791023078876139)
+(define b 2351399303373464486466122544523690094744975233415544072992656881240319)
+(define m 1e40)
+
+(powmod a b m)
+    → 1527229998585248450016808958343740453059
+
+;; powmod is a native function
+;; it could be defined as follows :
+
+(define (xpowmod base exp mod)
+    (define result 1)
+    (while ( !zero? exp)
+        (when (odd? exp) (set! result (% (* result base) mod)))
+    (/= exp 2)
+    (set! base (% (* base base) mod)))
+result)
+
+(xpowmod a b m)
+    → 1527229998585248450016808958343740453059