perl-Test-Number-Delta

Compare the difference between numbers against a given tolerance

At some point or another, most programmers find they need to compare floating-point numbers for equality. The typical idiom is to test if the absolute value of the difference of the numbers is within a desired tolerance, usually called epsilon. This module provides such a function for use with the Test::More manpage. Usage is similar to other test functions described in the Test::More manpage. Semantically, the 'delta_within' function replaces this kind of construct: ok ( abs($p - $q) < $epsilon, '$p is equal to $q' ) or diag "$p is not equal to $q to within $epsilon"; While there's nothing wrong with that construct, it's painful to type it repeatedly in a test script. This module does the same thing with a single function call. The 'delta_ok' function is similar, but either uses a global default value for epsilon or else calculates a 'relative' epsilon on the fly so that epsilon is scaled automatically to the size of the arguments to 'delta_ok'. Both functions are exported automatically. Because checking floating-point equality is not always reliable, it is not possible to check the 'equal to' boundary of 'less than or equal to epsilon'. Therefore, Test::Number::Delta only compares if the absolute value of the difference is *less than* epsilon (for equality tests) or *greater than* epsilon (for inequality tests).