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.Arr