There are some cases when we include .cpp file instead of standard header file (.h), for example:
#include "example.cpp"
instead of
#include "example.h"
It seems to work but is this safe or should I avoid it?
What about the compilation time?
It's lazy coding. Use header files. Yes they can increase compile time but they mean that you can easily re-implement chunks of your code, or better yet, another developer could at anytime. The header file serves as a template for what your C/C++
code is going to do. It's a bad idea to discard or ignore it.