Initial data commit

Task/Modular-exponentiation/D/modular-exponentiation.d

@@ -0,0 +1,30 @@
+module modular_exponentiation;
+
+private import std.bigint;
+
+BigInt powMod(BigInt base, BigInt exponent, in BigInt modulus)
+pure nothrow /*@safe*/ in {
+   assert(exponent >= 0);
+} body {
+    BigInt result = 1;
+
+    while (exponent) {
+        if (exponent & 1)
+            result = (result * base) % modulus;
+        exponent /= 2;
+        base = base ^^ 2 % modulus;
+    }
+
+    return result;
+}
+
+version (modular_exponentiation)
+    void main() {
+        import std.stdio;
+
+        powMod(BigInt("29883481620585741369158914214988194" ~
+                      "66320163312926952423791023078876139"),
+               BigInt("235139930337346448646612254452369009" ~
+                      "4744975233415544072992656881240319"),
+               BigInt(10) ^^ 40).writeln;
+    }