fabs, fabsf, fabsl, fabsd32, fabsd64, fabsd128 (original) (raw)

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)
_Decimal32 fabsd32( _Decimal32 arg );	(4)	(since C23)
_Decimal64 fabsd64( _Decimal64 arg );	(5)	(since C23)
_Decimal128 fabsd128( _Decimal128 arg );	(6)	(since C23)
Defined in header <tgmath.h>
#define fabs( arith )	(7)	(since C99)

1-6) Computes the absolute value of a floating-point value arg.

The functions with decimal floating-point parameters are declared if and only if the implementation predefines __STDC_IEC_60559_DFP__ (i.e. the implementation supports decimal floating-point numbers).	(since C23)

Type-generic macro: If the argument has type _Decimal128, _Decimal64, _Decimal32,(since C23)long double, double, or float, fabsd128, fabsd64, fabsd32,(since C23)fabsl, fabs, or fabsf is called, respectively. Otherwise, if the argument has integer type, fabs is called. Otherwise, if the argument is complex, then the macro invokes the corresponding complex function (cabsf, cabs, cabsl). Otherwise, the behavior is undefined.

[edit] Parameters

arg	-	floating-point value
arith	-	floating-point or integer value

[edit] Return value

If successful, returns the absolute value of arg (\(\small |arg| \)|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] Example

#include <math.h> #include <stdio.h> #define PI 3.14159 // This numerical integration assumes all area is positive. double integrate(double f(double), double a, double b, // assume a < b unsigned steps) // assume steps > 0 { const double dx = (b - a) / steps; double sum = 0.0; for (double x = a; x < b; x += dx) sum += fabs(f(x)); return dx * 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("Area under sin(x) in [-PI, PI] = %f\n", integrate(sin, -PI, PI, 5101)); }

Output:

fabs(+3) = 3.000000 fabs(-3) = 3.000000 fabs(-0) = 0.000000 fabs(-Inf) = inf Area under sin(x) in [-PI, PI] = 4.000000

[edit] References