ieee_functions(3) — Subroutines

NAME

copysign, finite, fp_class, isnan, nextafter, unordered − Related miscellaneous 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 standards 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 finitel(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 signaling 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); otherwise, 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).

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