Add gcd(a,b) and powermod(a,b,m).

src/net/apocalypselabs/symat/Functions.java

@@ -174,6 +174,24 @@ public class Functions {
         return fact.toString();
     }
 
+    /**
+     * Take (a^b) mod m.
+     * @param a Number
+     * @param b Exponent
+     * @param m Modulus
+     * @return pow(a,b)%m.
+     */
+    public double powermod(double a, double b, double m) {
+        return (pow(a, b) % m + m) % m;
+    }
+
+    public int gcd(int a, int b) {
+        if (b == 0) {
+            return a;
+        }
+        return gcd(b, a % b);
+    }
+
     /**
      * Differentiate the function with respect to idv.
      *