Function std.math.operations.nextafter
Calculates the next representable value after x in the direction of y.
T nextafter(T)
(
const T x,
const T y
) pure nothrow @nogc @safe;
If y > x, the result will be the next largest floating-point value; if y < x, the result will be the next smallest value. If x == y, the result is y. If x or y is a NaN, the result is a NaN.
Remarks
This function is not generally very useful; it's almost always better to use the faster functions nextUp() or nextDown() instead.
The FE_INEXACT and FE_OVERFLOW exceptions will be raised if x is finite and the function result is infinite. The FE_INEXACT and FE_UNDERFLOW exceptions will be raised if the function value is subnormal, and x is not equal to y.
Example
import std .math .traits : isNaN;
float a = 1;
assert(is(typeof(nextafter(a, a)) == float));
assert(nextafter(a, a .infinity) > a);
assert(isNaN(nextafter(a, a .nan)));
assert(isNaN(nextafter(a .nan, a)));
double b = 2;
assert(is(typeof(nextafter(b, b)) == double));
assert(nextafter(b, b .infinity) > b);
assert(isNaN(nextafter(b, b .nan)));
assert(isNaN(nextafter(b .nan, b)));
real c = 3;
assert(is(typeof(nextafter(c, c)) == real));
assert(nextafter(c, c .infinity) > c);
assert(isNaN(nextafter(c, c .nan)));
assert(isNaN(nextafter(c .nan, c)));
Authors
Walter Bright, Don Clugston, Conversion of CEPHES math library to D by Iain Buclaw and David Nadlinger