Apache C++ Standard Library User's Guide

## 20.1 Overview

The class complex is a template class used to create objects for representing and manipulating complex numbers. The operations defined on complex numbers allow them to be freely intermixed with the other numeric types available in the C++ language, thereby permitting numeric software to be easily and naturally expressed.

### 20.1.1 Include Files

Programs that use complex numbers must include the `complex` header file:

    #include <complex>