Advanced C++ Programming Cookbook

How to handle includes

In the preceding example, you might have noticed that, when we used our custom header-only library, we included the library first. This is an essential first step to writing a header-only library. When writing examples or tests for header-only libraries, our library should be the first thing we include to ensure that all of the header's dependencies are defined in the header-only library and not in our example or test.

For example, suppose we change our library as follows:

#ifndef MY_LIBRARY#define MY_LIBRARYnamespace library_name{    void my_api()    {        std::cout << "The answer is: 42" << '\n';    }}#endif

As shown in the preceding code snippet, instead of returning an integer our API now outputs to stdout. We can use our new ...