Define real() and imag() as functions to allow for overloading

src/include/types.h

@@ -62,7 +62,21 @@ typedef __complex__ double dcomplex;
 #endif // lapack_int
 #endif // np_int
 
-#define imag(z) ( __imag__ (z) )
-#define real(z) ( __real__ (z) )
 #define dconjg(z) ( (__real__ (z) - I * (__imag__ (z))) )
+
+/*! \brief Get the imaginary part of double precision complex number.
+ *
+ * \param z: `const dcomplex &` Reference to the complex number from
+ * which to extract the imaginary part.
+ * \return Im(z): `double` Imaginary part of z.
+ */
+double inline imag(const dcomplex &z) { return __imag__ z; }
+
+/*! \brief Get the imaginary part of double precision complex number.
+ *
+ * \param z: `const dcomplex &` Reference to the complex number from
+ * which to extract the real part.
+ * \return Re(z): `double` Real part of z.
+ */
+double inline real(const dcomplex &z) { return __real__ z; }
 #endif