функция абсолютного значения (absolute value function)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
fabs, fabsf, fabsl — absolute value function
Синопсис (Synopsis)
#include <math.h>
double fabs(double x);
float fabsf(float x);
long double fabsl(long double x);
Описание (Description)
The functionality described on this reference page is aligned
with the ISO C standard. Any conflict between the requirements
described here and the ISO C standard is unintentional. This
volume of POSIX.1‐2017 defers to the ISO C standard.
These functions shall compute the absolute value of their
argument x,|x|.
Возвращаемое значение (Return value)
Upon successful completion, these functions shall return the
absolute value of x.
If x is NaN, a NaN shall be returned.
If x is ±0, +0 shall be returned.
If x is ±Inf, +Inf shall be returned.
Ошибки (Error)
No errors are defined.
The following sections are informative.
Примеры (Examples)
Computing the 1-Norm of a Floating-Point Vector
This example shows the use of fabs() to compute the 1-norm of a
vector defined as follows:
norm1(v) = |v[0]| + |v[1]| + ... + |v[n-1]|
where |x| denotes the absolute value of x, n denotes the vector's
dimension v[i] denotes the i-th component of v (0≤i<n).
#include <math.h>
double
norm1(const double v[], const int n)
{
int i;
double n1_v; /* 1-norm of v */
n1_v = 0;
for (i=0; i<n; i++) {
n1_v += fabs (v[i]);
}
return n1_v;
}
Использование в приложениях (Application usage)
None.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
isnan(3p)
The Base Definitions volume of POSIX.1‐2017, math.h(0p)
