fabs, fabsf, fabsl

Functions

Basic operations

abslabsllabsimaxabs (C99)
fabs
divldivlldivimaxdiv (C99)
fmod

remainder (C99)
remquo (C99)
fma (C99)
fmax (C99)
fmin (C99)
fdim (C99)
nannanfnanl (C99)(C99)(C99)

Exponential functions

exp
exp2 (C99)
expm1 (C99)

log
log10
log1p (C99)
log2 (C99)

Power functions

sqrt
cbrt (C99)

hypot (C99)
pow

Trigonometric and hyperbolic functions

sin
cos
tan
asin
acos
atan
atan2

sinh
cosh
tanh
asinh (C99)
acosh (C99)
atanh (C99)

Error and gamma functions

erf (C99)
erfc (C99)

lgamma (C99)
tgamma (C99)

Nearest integer floating point operations

ceil
floor
roundlroundllround (C99)(C99)(C99)

trunc (C99)
nearbyint (C99)
rintlrintllrint (C99)(C99)(C99)

Floating point manipulation functions

ldexp
scalbnscalbln (C99)(C99)
ilogb (C99)
logb (C99)

frexp
modf
nextafternexttoward (C99)(C99)
copysign (C99)

Classification

fpclassify (C99)
isfinite (C99)
isinf (C99)
isnan (C99)
isnormal (C99)
signbit (C99)

isgreater (C99)
isgreaterequal (C99)
isless (C99)
islessequal (C99)
islessgreater (C99)
isunordered (C99)

Types

div_tldiv_tlldiv_timaxdiv_t

(C99)(C99)

float_tdouble_t

(C99)(C99)

Macro constants

HUGE_VALFHUGE_VALHUGE_VALL (C99)(C99)
FP_FAST_FMAFFP_FAST_FMAFP_FAST_FMAL (C99)(C99)(C99)
math_errhandlingMATH_ERRNOMATH_ERRNOEXCEPT (C99)(C99)(C99)

INFINITY (C99)
NAN (C99)
FP_ILOGB0FP_ILOGBNAN (C99)(C99)
FP_NORMALFP_SUBNORMALFP_ZEROFP_INFINITEFP_NAN (C99)(C99)(C99)(C99)(C99)

Defined in header `<math.h>`
float fabsf( float arg );	(1)	(since C99)
double fabs( double arg );	(2)
long double fabsl( long double arg );	(3)	(since C99)
Defined in header `<tgmath.h>`
#define fabs( arg )	(4)	(since C99)

1-3) Computes the absolute value of a floating point value arg.

4) Type-generic macro: If the argument has type long double, fabsl is called. Otherwise, if the argument has integer type or has type double, fabs is called. Otherwise, fabsf is called. If the argument is complex, then the macro invokes the corresponding complex function (cabsf, cabs, cabsl).

Parameters

arg

-

floating point 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

Example

Run this code

#include <stdio.h>
#include <math.h>

/* This numerical integration assumes all area is positive. */
#define PI 3.14159
double num_int (double a, double b,
                double f(double),
                unsigned n) {
    if (a == b) return 0.0;
    if (n == 0) n=1;   /* avoid division by zero */
    double h = (b-a)/n;
    double sum = 0.0;
    for (unsigned k=0; k < n; ++k)
        sum += h*fabs(f(a+k*h));
    return sum;
}

int main(void)
{
    printf("fabs(+3) =%f\n", fabs(+3.0));
    printf("fabs(-3) =%f\n", fabs(-3.0));
    // special values
    printf("fabs(-0) =%f\n", fabs(-0.0));
    printf("fabs(-Inf) =%f\n", fabs(-INFINITY));

    printf("%f\n", num_int(0.0,2*PI,sin,100000));

}

Output:

fabs(+3) = 3.000000
fabs(-3) = 3.000000
fabs(-0) = 0.000000
fabs(-Inf) = inf
4.000000

References

C11 standard (ISO/IEC 9899:2011):

7.12.7.2 The fabs functions (p: 248)

7.25 Type-generic math <tgmath.h> (p: 373-375)

C99 standard (ISO/IEC 9899:1999):

7.12.7.2 The fabs functions (p: 228-229)

7.22 Type-generic math <tgmath.h> (p: 335-337)

C89/C90 standard (ISO/IEC 9899:1990):

4.5.6.2 The fabs function

Language
Headers
Type support
Program utilities
Variadic function support
Error handling
Dynamic memory management
Date and time utilities
Strings library
Algorithms
Numerics
Input/output support
Localization support
Atomic operations (C11)
Thread support (C11)
Technical Specifications

Common mathematical functions
Floating-point environment
Complex number arithmetics
Random number generation
Type-generic math