How do I fix an “ambiguous” function call?

Question

I\'m working on a C++ program for class, and my compiler is complaining about an \"ambiguous\" function call. I suspect that this is because there are several functions defined

Answer 1

The abs function included by is overloaded for int and long and long long. Since you give a double as the argument, the compiler does not have an exact fit, so it tries to convert the double to a type that abs accepts, but it does not know if it should try to convert it to int, long, or long long, hence it's ambiguous.

But you probably really want the abs that takes a double and returns a double. For this you need to include . Since the double argument matches exactly, the compiler will not complain.

It seems that gets included automatically when you include the other headers which should not happen. The compiler should have given error: ‘abs’ was not declared in this scope or something similar.