std::abs(float), std::fabs, std::fabsf, std::fabsl
| Defined in header <cmath>
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| Defined in header <cstdlib>
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| (1) | ||
float abs( float num ); double abs( double num ); |
(until C++23) | |
| constexpr /* floating-point-type */ abs( /* floating-point-type */ num ); |
(since C++23) | |
| Defined in header <cmath>
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| (2) | ||
float fabs ( float num ); double fabs ( double num ); |
(until C++23) | |
| constexpr /* floating-point-type */ fabs ( /* floating-point-type */ num ); |
(since C++23) | |
float fabsf( float num ); |
(3) | (since C++11) (constexpr since C++23) |
long double fabsl( long double num ); |
(4) | (since C++11) (constexpr since C++23) |
| Additional overloads (since C++11) |
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| Defined in header <cmath>
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template< class Integer > double fabs ( Integer num ); |
(A) | (since C++11) (constexpr since C++23) |
std::abs and std::fabs for all cv-unqualified floating-point types as the type of the parameter num.(since C++23)|
A) Additional overloads are provided for all integer types, which are treated as double.
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(since C++11) |
For integral arguments, the integral overloads of std::abs are likely better matches. If std::abs is called with an unsigned integral argument that cannot be converted to int by integral promotion, the program is ill-formed.
Contents |
[edit] Parameters
| num | - | floating-point or integer value |
[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
The additional overloads are not required to be provided exactly as (A). They only need to be sufficient to ensure that for their argument num of integer type, std::fabs(num) has the same effect as std::fabs(static_cast<double>(num)).
[edit] Example
#include <cmath> #include <iostream> 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' << "abs(-NaN) = " << std::abs(-NAN) << '\n'; }
Possible output:
abs(+3.0) = 3 abs(-3.0) = 3 abs(-0.0) = 0 abs(-Inf) = inf abs(-NaN) = nan
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 2192 | C++98 | overloads of std::abs wereinconsistently declared in two headers |
declared these overloads in both headers |
| LWG 2735 | C++11 | overloads of std::abs for integer typesreturning double was erroneously required |
removed the requirement |
[edit] See also
| (C++11) |
computes absolute value of an integral value (|x|) (function) |
| (C++11)(C++11)(C++11) |
copies the sign of a floating point value (function) |
| (C++11) |
checks if the given number is negative (function) |
| returns the magnitude of a complex number (function template) | |
| applies the function abs to each element of valarray (function template) | |
| C documentation for fabs
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