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The latest version of this topic can be found at <ccomplex>.

Includes the STL header <complex>, which effectively includes the Standard C library header <complex.h> and adds the associated names to the std namespace.

#include <ccomplex>  

Including this header ensures that the names declared using external linkage in the Standard C library header are declared in the std namespace.

The name clog, which is declared in <complex.h>, is not defined in the std namespace because of potential conflicts with the clog that is declared in <iostream>.

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