Ranged-sets

Ranged sets for Haskell.

A ranged set is an ordered list of ranges. This allows sets such as all reals x such that:

(0.25 < x <= 0.75 or 1.4 <= x < 2.3 or 4.5 < x)

Alternatively you can have all strings s such that:

   ("F" <= s < "G")