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)));
Calculates the next representable value after x in the direction of y.
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.