ReversibleBoundedEnum.hs

{-
	Copyright (C) 2012 Dr. Alistair Ward

	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program.  If not, see <http://www.gnu.org/licenses/>.
-}
{- |
 [@AUTHOR@]	Dr. Alistair Ward

 [@DESCRIPTION@]	Facilities testing of custom implementations of 'Enum'.
-}

module ToolShed.Test.ReversibleBoundedEnum(
-- * Functions
-- ** Predicates
	isReversible
) where

-- | Checks that composing 'pred' & 'succ' is equivalent to the identity.
isReversible :: (Bounded r, Eq r, Enum r) => r -> Bool
isReversible r
	| r == minBound	= pred (succ r) == r
	| otherwise	= succ (pred r) == r