Add more construectors

cnumber.hpp

@@ -22,14 +22,26 @@ public:
     r = a;
     i = b;
   }
+  cnumber(const fraction &a) {
+    r = a;
+    i = 0;
+  }
   cnumber(int a, int b) {
     r = a;
     i = b;
   }
+  cnumber(int a) {
+    r = a;
+    i = 0;
+  }
   cnumber(double a, double b) {
     r = a;
     i = b;
   }
+  cnumber(double a) {
+    r = a;
+    i = 0;
+  }
   ~cnumber() {}
   // Member functions
   cnumber conjugate() const {