Tribblix: manual page: nextafter.3m

NEXTAFTER(3M) Mathematical Library Functions NEXTAFTER(3M)

NAME

nextafter, nextafterf, nextafterl, nexttoward, nexttowardf,
nexttowardl - next representable double-precision floating-point
number

SYNOPSIS

c99 [ flag... ] file... -lm [ library... ]
#include <math.h>

double nextafter(double x, double y);

float nextafterf(float x, float y);

long double nextafterl(long double x, long double y);

double nexttoward(double x, long double y);

float nexttowardf(float x, long double y);

long double nexttowardl(long double x, long double y);

DESCRIPTION

The nextafter(), nextafterf(), and nextafterl() functions compute the
next representable floating-point value following x in the direction
of y. Thus, if y is less than x, nextafter() returns the largest
representable floating-point number less than x. The nextafter(),
nextafterf(), and nextafterl() functions return y if x equals y.

The nexttoward(), nexttowardf(), and nexttowardl() functions are
equivalent to the corresponding nextafter() functions, except that
the second parameter has type long double and the functions return y
converted to the type of the function if x equals y.

RETURN VALUES

Upon successful completion, these functions return the next
representable floating-point value following x in the direction of y.

If x == y, y (of the type x) is returned.

If x is finite and the correct function value would overflow, a range
error occurs and +-HUGE_VAL, +-HUGE_VALF, and +-HUGE_VALL (with the
same sign as x) is returned as appropriate for the return type of the
function.

If x or y is NaN, a NaN is returned.

If x != y and the correct function value is subnormal, zero, or
underflows, a range error occurs and either the correct function
value (if representable) or 0.0 is returned.

ERRORS

These functions will fail if:

Range Error
The correct value overflows.

If the integer expression (math_errhandling &
MATH_ERREXCEPT) is non-zero, the overflow floating-
point exception is raised.

The nextafter() function sets errno to ERANGE if the
correct value would overflow.

Range Error
The correct value underflows.

If the integer expression (math_errhandling &
MATH_ERREXCEPT) is non-zero, the underflow floating-
point exception is raised.

USAGE

An application wanting to check for exceptions should call
feclearexcept(FE_ALL_EXCEPT) before calling these functions. On
return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW |
FE_UNDERFLOW) is non-zero, an exception has been raised. An
application should either examine the return value or check the
floating point exception flags to detect exceptions.

An application can also set errno to 0 before calling nextafter().
On return, if errno is non-zero, an error has occurred. The
nextafterf(), nextafterl(). nexttoward(), nexttowardf(), and
nexttowardl() functions do not set errno.

ATTRIBUTES