-----------------------------------------------------------------------------
-- |
-- Module : Data.Ix
-- Copyright : (c) The University of Glasgow 2001
-- License : BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer : libraries@haskell.org
-- Stability : provisional
-- Portability : portable
--
-- Class of index types.
--
-- The 'Ix' class is used to map a continuous subrange of values in a type onto
-- integers. It is used primarily for array indexing (see Section 6
-- <http://www.haskell.org/onlinelibrary/array.html#arrays>). The 'Ix'
-- class contains the methods range, index, and inRange. The 'index' operation
-- maps a bounding pair, which defines the lower and upper bounds of the range,
-- and a subscript, to an integer. The 'range' operation enumerates all
-- subscripts; the 'inRange' operation tells whether a particular subscript
-- lies in the range defined by a bounding pair.
--
-- An implementation is entitled to assume the following laws about these
-- operations:
--
-- > range (l,u) !! index (l,u) i == i -- when i is in range
--
-- > inRange (l,u) i == i `elem` range (l,u)
--
-----------------------------------------------------------------------------
module Data.Ix
(
Ix
( range -- :: (Ix a) => (a,a) -> [a]
, index -- :: (Ix a) => (a,a) -> a -> Int
, inRange -- :: (Ix a) => (a,a) -> a -> Bool
, rangeSize -- :: (Ix a) => (a,a) -> Int
)
-- Ix instances:
--
-- Ix Char
-- Ix Int
-- Ix Integer
-- Ix Bool
-- Ix Ordering
-- Ix ()
-- (Ix a, Ix b) => Ix (a, b)
-- ...
-- Implementation checked wrt. Haskell 98 lib report, 1/99.
-- * 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 Figure 1
-- <http://www.haskell.org/onlinelibrary/ix.html#prelude-index>.
) where
import Prelude
import Hugs.Prelude( Ix(..) )