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 repre‐
sentable 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 equiv‐
alent to the corresponding nextafter() functions, except that the sec‐
ond 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 repre‐
sentable 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 func‐
tion.
If x or y is NaN, a NaN is returned.
If x != y and the correct function value is subnormal, zero, or under‐
flows, 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 feclearex‐
cept(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
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Standard │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │MT-Safe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOfeclearexcept(3M), fetestexcept(3M), math.h(3HEAD), attributes(5),
standards(5)SunOS 5.10 12 Jul 2006 nextafter(3M)
