std:: abs (float) , std:: fabs, std:: fabsf, std:: fabsl
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Defined in header
<cmath>
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Defined in header
<cstdlib>
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| (1) | ||
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float
abs
(
float
num
)
;
double
abs
(
double
num
)
;
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(until C++23) | |
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constexpr
/* floating-point-type */
abs ( /* floating-point-type */ num ) ; |
(since C++23) | |
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Defined in header
<cmath>
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| (2) | ||
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float
fabs
(
float
num
)
;
double
fabs
(
double
num
)
;
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(until C++23) | |
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constexpr
/* floating-point-type */
fabs ( /* floating-point-type */ num ) ; |
(since C++23) | |
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float
fabsf
(
float
num
)
;
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(3) |
(since C++11)
(constexpr since C++23) |
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long
double
fabsl
(
long
double
num
)
;
|
(4) |
(since C++11)
(constexpr since C++23) |
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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
.
|
(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.
Parameters
| num | - | floating-point or integer value |
Return value
If successful, returns the absolute value of
arg
(
|arg|
). The value returned is exact and does not depend on any rounding modes.
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.
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 ) ) .
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
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
were
inconsistently declared in two headers |
declared these overloads
in both headers |
| LWG 2735 | C++11 |
overloads of
std::abs
for integer types
returning double was erroneously required |
removed the requirement |
See also
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(C++11)
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computes absolute value of an integral value (
|x|
)
(function) |
|
(C++11)
(C++11)
(C++11)
|
copies the sign of a floating point value
(function) |
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(C++11)
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checks if the given number is negative
(function) |
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returns the magnitude of a complex number
(function template) |
|
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applies the function
abs
to each element of valarray
(function template) |
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C documentation
for
fabs
|
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