ieee_functions(3)ieee_functions(3)NAME
copysign, finite, fp_class, isnan, nextafter, unordered - Related mis‐
cellaneous IEEE arithmetic functions.
SYNOPSIS
#include <math.h>
double copysign(
double x,
double y ); float copysignf(
float x,
float y ); long double copysignl(
long double x,
long double y ); int finite(
double x ); int finitef(
float x ); int finitel(
long double x ); int fp_class(
double x ); int fp_classf(
float x ); int fp_classl(
long double x ); int isnan(
double x ); int isnanf(
float x ); int isnanl(
long double x ); double nextafter(
double x,
double y ); float nextafterf(
float x,
float y ); long double nextafterl(
long double x,
long double y ); int unordered(
double x,
double y ); int unorderedf(
float x,
float y ); int unorderedl(
long double x,
long double y );
LIBRARY
Math Library (libm)
STANDARDS
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
isnan(): XPG4
nextafter(): XPG4-UNIX
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
DESCRIPTION
The copysign(), copysignf(), and copysignl() functions return x with
the same sign as y. IEEE 754 requires copysign(x,NaN), copysignf(x,NaN)
and copysignl(x,NaN) to return +x or -x.
The finite(), finitef(), and finitel() functions return the integer
value 1 (True) or 0 (False). The finite(x), finitef(x), and fini‐
tel(x) functions return 1 when -infinity < x< +infinity. They return 0
when |x| = infinity or x is a NaN.
The fp_class(), fp_classf(), and fp_classl() functions determine the
class of an IEEE floating-point value. They return one of the constants
in the file <fp_class.h> and never cause an exception, even for signal‐
ing NaNs. These routines implement the recommended function class(x) in
the appendix of the IEEE 754-1985 standard for binary floating-point
arithmetic. The constants in <fp_class.h> refer to the following
classes of values:
─────────────────────────────────────────────
Constant Class
─────────────────────────────────────────────
FP_SNAN Signaling NaN (Not-a-Number)
FP_QNAN Quiet NaN (Not-a-Number)
FP_POS_INF +infinity
FP_NEG_INF -infinity
FP_POS_NORM Positive normalized
FP_NEG_NORM Negative normalized
FP_POS_DENORM Positive denormalized
FP_NEG_DENORM Negative denormalized
FP_POS_ZERO +0.0 (positive zero)
FP_NEG_ZERO -0.0 (negative zero)
─────────────────────────────────────────────
The isnan(), isnanf(), and isnanl() functions return the value 1 (True)
if x is NaN (the IEEE floating point reserved not-a-number value); oth‐
erwise, it returns the value 0 (False).
The nextafter(), nextafterf(), and nextafterl() functions return the
next machine-representable number from x in the direction of y.
The unordered(), unorderedf(), and unorderedl() functions return the
value 1 (True) if either x or y or both is a NaN; otherwise, it returns
the value 0 (False).
SEE ALSOdrem(3), logb(3), scalb(3), rint(3), sqrt(3), and ANSI/IEEE Std
754-1985, IEEE Standard for Binary Floating-Point Arithmetic
ieee_functions(3)
