diff --git a/include/complex.hpp b/include/complex.hpp
index 8771583..f42143d 100644
--- a/include/complex.hpp
+++ b/include/complex.hpp
@@ -3,6 +3,8 @@
 
 #include <iostream>
 
+#include <math.h>
+
 /*! @file complex.hpp
 *  @brief Complex numbers and related computation
 */
@@ -18,30 +20,36 @@ namespace ztd
     //! @brief Contructor z
     complex(const complex& z);
 
+    inline complex& operator=(const complex& z) { real=z.real; im=z.im; return *this;}
+
     //! @brief Complex Addition
-    complex& operator+=(const complex& z);
+    complex& operator+=(complex z);
     //! @brief Complex Substraction
-    complex& operator-=(const complex& z);
+    complex& operator-=(complex z);
     //! @brief Complex Multiplication
-    complex& operator*=(const complex& z);
+    complex& operator*=(complex z);
     //! @brief Complex Division
-    complex& operator/=(const complex& z);
+    complex& operator/=(complex z);
+
 
     //! @brief Real part
     double real;
     //! @brief Imaginary part
     double im;
 
+    inline double mod() { return sqrt(real*real + im*im); }
+    double arg() { return atan2(real, im); }
+
   };
 
   //! @brief Complex Addition
-  inline complex operator+(const complex& z1, const complex& z2) { complex z3(z1); return z3 += z1; }
+  inline complex operator+(complex z1, const complex& z2) { return z1 += z2; }
   //! @brief Complex Substraction
-  inline complex operator-(const complex& z1, const complex& z2) { complex z3(z1); return z3 -= z1; }
+  inline complex operator-(complex z1, const complex& z2) { return z1 -= z2; }
   //! @brief Complex Multiplication
-  inline complex operator*(const complex& z1, const complex& z2) { complex z3(z1); return z3 *= z1; }
+  inline complex operator*(complex z1, const complex& z2) { return z1 *= z2; }
   //! @brief Complex Division
-  inline complex operator/(const complex& z1, const complex& z2) { complex z3(z1); return z3 /= z1; }
+  inline complex operator/(complex z1, const complex& z2) { return z1 /= z2; }
 
   //! @brief Output a+bi
   inline std::ostream& operator<<(std::ostream& stream, complex z) { stream << z.real << '+' << z.im << 'i'; return stream; }
diff --git a/src/complex.cpp b/src/complex.cpp
index c55ca57..dfafbbf 100644
--- a/src/complex.cpp
+++ b/src/complex.cpp
@@ -13,26 +13,26 @@ ztd::complex::complex(const ztd::complex& z)
   im=z.im;
 }
 
-ztd::complex& ztd::complex::operator+=(const ztd::complex& z)
+ztd::complex& ztd::complex::operator+=(ztd::complex z)
 {
   real += z.real;
   im += z.im;
   return *this;
 }
-ztd::complex& ztd::complex::operator-=(const ztd::complex& z)
+ztd::complex& ztd::complex::operator-=(ztd::complex z)
 {
   real -= z.real;
   im -= z.im;
   return *this;
 }
-ztd::complex& ztd::complex::operator*=(const ztd::complex& z)
+ztd::complex& ztd::complex::operator*=(ztd::complex z)
 {
   double r=real;
   real = real*z.real - im*z.im;
   im = r*z.im + im*z.real;
   return *this;
 }
-ztd::complex& ztd::complex::operator/=(const ztd::complex& z)
+ztd::complex& ztd::complex::operator/=(ztd::complex z)
 {
   double r=real;
   double div = z.real*z.real + z.im*z.im;