28 Numerics library [numerics]

28.7 Mathematical functions for floating-point types [c.math]

28.7.2 Absolute values [c.math.abs]

[Note 1:

The headers <cstdlib> and <cmath> declare the functions described in this subclause.

— end note]

constexpr int abs(int j);
constexpr long int abs(long int j);
constexpr long long int abs(long long int j);
constexpr float abs(float j);
constexpr double abs(double j);
constexpr long double abs(long double j);

Effects: The abs functions have the semantics specified in the C standard library for the functions abs, labs, llabs, fabsf, fabs, and fabsl.

Remarks: If abs() is called with an argument of type X for which is_unsigned_v<X> is true and if X cannot be converted to int by integral promotion, the program is ill-formed.

[Note 2:

Arguments that can be promoted to int are permitted for compatibility with C.

— end note]