fabs, fabsf, fabsl
From cppreference.com
| Defined in header <math.h>
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| 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>
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| #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
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) |
| C++ documentation for fabs
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