What's the difference between abs and fabs?

Question

I checked the difference between abs and fabs on python here

As I understand there are some difference regarding the speed and the passed t

Answer 1

My Visual C++ 2008 didn't know which to choice from long double fabs(long double), float fabs(float), or double fabs(double).

In the statement double i = -9;, the compiler will know that -9 should be converted to double because the type of i is double.

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abs() is declared in stdlib.h and it will deal with int value.

fabs() is declared in math.h and it will deal with double value.