Double precision floating point values can only represent a limited series of natural numbers. For example, the values 2.0000000000000000 and 2.0000000000000004 can be stored in a double, but nothing inbetween them.

This comparison will count how many possible double precision floating point values are between the left and the right number. If the number of possible values between both numbers is less than or equal to maxUlps, then the numbers are considered as being equal.

Implementation partially follows the code outlined here: http://www.anttirt.net/2007/08/19/proper-floating-point-comparisons/