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

Functions

Basic operations

abs(int)labsllabsimaxabs (C++11)
abs(float)fabs
divldivlldivimaxdiv (C++11)
fmod

remainder (C++11)
remquo (C++11)
fma (C++11)
fmax (C++11)
fmin (C++11)
fdim (C++11)
nannanfnanl (C++11)(C++11)(C++11)

Exponential functions

exp
exp2 (C++11)
expm1 (C++11)

log
log10
log1p (C++11)
log2 (C++11)

Power functions

sqrt
cbrt (C++11)

hypot (C++11)
pow

Trigonometric and hyperbolic functions

sin
cos
tan
asin
acos
atan
atan2

sinh
cosh
tanh
asinh (C++11)
acosh (C++11)
atanh (C++11)

Error and gamma functions

erf (C++11)
erfc (C++11)

lgamma (C++11)
tgamma (C++11)

Nearest integer floating point operations

ceil
floor
roundlroundllround (C++11)(C++11)(C++11)

trunc (C++11)
nearbyint (C++11)
rintlrintllrint (C++11)(C++11)(C++11)

Floating point manipulation functions

ldexp
scalbnscalbln (C++11)(C++11)
ilogb (C++11)
logb (C++11)

frexp
modf
nextafternexttoward (C++11)(C++11)
copysign (C++11)

Classification/Comparison

fpclassify (C++11)
isfinite (C++11)
isinf (C++11)
isnan (C++11)
isnormal (C++11)
signbit (C++11)

isgreater (C++11)
isgreaterequal (C++11)
isless (C++11)
islessequal (C++11)
islessgreater (C++11)
isunordered (C++11)

Macro constants

HUGE_VALFHUGE_VALHUGE_VALL (C++11)(C++11)
INFINITY (C++11)
NAN (C++11)
math_errhandlingMATH_ERRNOMATH_ERREXCEPT (C++11)

FP_NORMALFP_SUBNORMALFP_ZEROFP_INFINITEFP_NAN

(C++11)(C++11)(C++11)(C++11)(C++11)

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( IntegralType 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)

Parameters

arg

-

Value of a floating-point or Integral type

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

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.

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

Language
Headers
Freestanding and hosted implementations
Named requirements
Language support library
Concepts library (C++20)
Diagnostics library
Utilities library
Strings library
Containers library
Algorithms library
Iterators library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Filesystem library (C++17)
Technical Specifications

Common mathematical functions
Special mathematical functions
Floating-point environment (C++11)
Complex numbers
Numeric arrays
Pseudo-random number generation
Compile-time rational arithmetic (C++11)
Numeric algorithms
gcd (C++17)
lcm (C++17)
Generic numeric operations
iota (C++11)
accumulate
inner_product
adjacent_difference
partial_sum
reduce (C++17)
transform_reduce (C++17)
inclusive_scan (C++17)
exclusive_scan (C++17)
transform_inclusive_scan (C++17)
transform_exclusive_scan (C++17)
Bit operations
bit_cast (C++20)
ispow2 (C++20)
ceil2 (C++20)
floor2 (C++20)
log2p1 (C++20)