fmod computes the floating-point remainder of dividing x by y. The return
value is x - n * y, where n is the quotient of x / y, rounded toward zero to an integer.
nextafter returns the next representable floating-point value following x in the
direction of y. If y is less than x, these functions will return the largest representable
number less than x.
remainder compute the remainder of dividing x by y. The return value is x-ny, where
n is the value x / y, rounded to the nearest integer. If the absolute value of x-ny is
0.5, n is chosen to be even.