Add default constructor

cnumber.hpp

@@ -10,6 +10,10 @@ private:
 
 public:
   // Constructor
+  cnumber() {
+    r = 0;
+    i = 0;
+  }
   cnumber(const cnumber &z) {
     r = z.r;
     i = z.i;
@@ -26,6 +30,7 @@ public:
     r = a;
     i = b;
   }
+  ~cnumber() {}
   // Member functions
   cnumber conjugate() const {
     fraction a(this->r.get_n(), this->r.get_d());