/C

# fabs, fabsf, fabsl

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

```#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