fabs, fabsf, fabsl
Defined in header <math.h>
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(1) | (since C99) |
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(2) | |
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(3) | (since C99) |
Defined in header <tgmath.h>
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(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 (p: 373-375)
C99 standard (ISO/IEC 9899:1999):
- 7.12.7.2 The fabs functions (p: 228-229)
- 7.22 Type-generic math (p: 335-337)
C89/C90 standard (ISO/IEC 9899:1990):
- 4.5.6.2 The fabs function
See also
(C99) |
computes absolute value of an integral value (|x|) (function) |
(C99)(C99)(C99) |
produces a value with the magnitude of a given value and the sign of another given value (function) |
(C99) |
checks if the given number is negative (function) |
(C99)(C99)(C99) |
computes the magnitude of a complex number (function) |
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