Error: main.cpp: warning: using directive refers to implicitly-defined namespace ‘std’

If you see the following error when trying to compile a C++ application:

main.cpp: : : warning: using directive refers to implicitly-defined namespace 'std'

then that means you do not have any header file inclusion that uses std namespace.

You can fix this warning by including a C++ header file that uses a std namespace otherwise the compile will not know about std namespace.

How to Solve this Error:

#include <iostream>

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