Function std.math.nextafter

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.

Prototype

T nextafter(T)(
  T x,
  T y
) pure nothrow @nogc @safe;

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

float a = 1;
assert(is(typeof(nextafter(a, a)) == float));
assert(nextafter(a, a.infinity) > a);

double b = 2;
assert(is(typeof(nextafter(b, b)) == double));
assert(nextafter(b, b.infinity) > b);

real c = 3;
assert(is(typeof(nextafter(c, c)) == real));
assert(nextafter(c, c.infinity) > c);
}

//real nexttoward(real x, real y) { return core.stdc.math.nexttowardl(x, y); }

/*******************************************
* Returns the positive difference between x and y.
* Returns:
*      *      x, y       fdim(x, y)
*      x > y  x - y
*      x <= y +0.0
*      
*/
real fdim(real x, real y) @safe pure nothrow @nogc { return (x > y) ? x - y : +0.0;