The nextafter() functions
return the next representable neighbor of x in the direction towards
y. The size of the
step between x and
the result depends on the type of the result. If x = y the function simply returns
y. If either value is
NaN, then
NaN is returned.
Otherwise a value corresponding to the value of the least
significant bit in the mantissa is added or subtracted,
depending on the direction.
The nexttoward() functions
do the same as the nextafter()
functions, except that they have a long double second
argument.
These functions will signal overflow or underflow if the
result goes outside of the range of normalized numbers.
CONFORMING TO
C99. This function is defined in IEC 559 (and the appendix
with recommended functions in IEEE 754/IEEE 854).