arg
. The functions with decimal floating point parameters are declared if and only the implementation predefines | (since C23) |
_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.arg | - | floating point value |
arith | - | floating point or integer 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.
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),
#include <stdio.h> #include <math.h> #define PI 3.14159 /* This numerical integration assumes all area is positive. */ double integrate(double a, double b, /* assume a < b */ double f(double), 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("%f\n", integrate(-PI,+PI,sin,10*1000)); }
Output:
(C99) | computes absolute value of an integral value (\(\small{|x|}\)|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 macro) |
(C99)(C99)(C99) | computes the magnitude of a complex number (function) |
C++ documentation for fabs |
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