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# std::abs(float), std::fabs

From cppreference.com
< cpp‎ | numeric‎ | math

Defined in header `<cmath>` |  |
Defined in header `<cstdlib>` |  | (since C++17)
float abs( float arg ); | (1) |
double abs( double arg ); | (2) |
long double abs( long double arg ); | (3) |
Defined in header `<cmath>` |  |
float fabs( float arg ); | (4) |
double fabs( double arg ); | (5) |
long double fabs( long double arg ); | (6) |
double fabs( Integral arg ); | (7) | (since C++11)

1-6) Computes the absolute value of a floating point value `arg`.
7) A set of overloads or a function template for all combinations of arguments of arithmetic type not covered by (4-6). If any argument has integral type, it is cast to double. If any other argument is long double, then the return type is long double, otherwise it is double.

For integral arguments, the integral overloads of `std::abs` are likely better matches. If `std::abs` is called with an argument of type `X` such that std::is_unsigned<X>::value is `true` and `X` cannot be converted to int by integral promotion, the program is ill-formed. | (since C++17)

### [edit] Parameters

arg | - | Value of a floating-point or Integral type

### [edit] Return value

If successful, returns the absolute value of `arg` (`|arg|`). The value returned is exact and does not depend on any rounding modes.

### [edit] Error handling

This function is not subject to any of the error conditions specified in math_errhandling

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

- If the argument is ±0, +0 is returned
- If the argument is ±∞, +∞ is returned
- If the argument is NaN, NaN is returned

### [edit] Notes

Between C++11 and C++14, the standard erroneously required `std::abs` to have overloads for integer types returning double. This requirement was removed in C++17 by defect report 2735.

### [edit] Example

Run this code

    #include <iostream>
    #include <cmath>

    int main()
    {
        std::cout << "abs(+3.0) = " << std::abs(+3.0) << '\n'
                  << "abs(-3.0) = " << std::abs(-3.0) << '\n';
        // special values
        std::cout << "abs(-0.0) = " << std::abs(-0.0) << '\n'
                  << "abs(-Inf) = " << std::abs(-INFINITY) << '\n';
    }

Possible output:

    abs(+3.0) = 3
    abs(-3.0) = 3
    abs(-0.0) = 0
    abs(-Inf) = inf

### [edit] See also

abs(int)labs llabs (C++11) | computes absolute value of an integral value (|x|) (function) [edit]
copysign (C++11) | copies the sign of a floating point value (function) [edit]
signbit (C++11) | checks if the given number is negative (function) [edit]
abs(std::complex) | returns the magnitude of a complex number (function template) [edit]
abs(std::valarray) | applies the function std::abs to each element of valarray (function template) [edit]
C documentation for fabs

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