validity typeclass

 Note: There are companion instance packages for this library:
  * validity-aeson
  * validity-bytestring
  * validity-containers
  * validity-path
  * validity-scientific
  * validity-text
  * validity-time
  * validity-unordered-containers
  * validity-uuid
  * validity-vector
 .
 This package provides a library for the Haskell programming language.
 See http://www.haskell.org/ for more information on Haskell.