Data/Ix.hs

{-# LANGUAGE Trustworthy #-}

-----------------------------------------------------------------------------
-- |
-- Module : Data.Ix
-- Copyright : (c) The University of Glasgow 2001
-- License : BSD-style (see the file libraries/base/LICENSE)
-- 
-- Maintainer : libraries@haskell.org
-- Stability : stable
-- Portability : portable
--
-- The 'Ix' class is used to map a contiguous subrange of values in
-- type onto integers. It is used primarily for array indexing
-- (see the array package). 'Ix' uses row-major order.
-- 
-----------------------------------------------------------------------------

module Data.Ix
 (
 -- * The 'Ix' class
 Ix
 ( range
 , index
 , inRange
 , rangeSize
 )
 -- Ix instances:
 --
 -- Ix Char
 -- Ix Int
 -- Ix Integer
 -- Ix Bool
 -- Ix Ordering
 -- Ix ()
 -- (Ix a, Ix b) => Ix (a, b)
 -- ...

 -- * Deriving Instances of 'Ix'
 -- | Derived instance declarations for the class 'Ix' are only possible
 -- for enumerations (i.e. datatypes having only nullary constructors)
 -- and single-constructor datatypes, including arbitrarily large tuples,
 -- whose constituent types are instances of 'Ix'. 
 -- 
 -- * For an enumeration, the nullary constructors are assumed to be
 -- numbered left-to-right with the indices being 0 to n-1 inclusive. This
 -- is the same numbering defined by the 'Enum' class. For example, given
 -- the datatype: 
 -- 
 -- > data Colour = Red | Orange | Yellow | Green | Blue | Indigo | Violet
 -- 
 -- we would have: 
 -- 
 -- > range (Yellow,Blue) == [Yellow,Green,Blue]
 -- > index (Yellow,Blue) Green == 1
 -- > inRange (Yellow,Blue) Red == False
 -- 
 -- * For single-constructor datatypes, the derived instance declarations
 -- are as shown for tuples in chapter 19, section 2 of the Haskell 2010 report:
 -- <https://www.haskell.org/onlinereport/haskell2010/haskellch19.html>.

 ) where

import GHC.Ix