Copyright	(c) The University of Glasgow 2001
License	BSD-style (see the file libraries/base/LICENSE)
Maintainer	libraries@haskell.org
Stability	stable
Portability	portable
Safe Haskell	Trustworthy
Language	Haskell2010

Data.Ix

Contents

The Ix class
Deriving Instances of Ix

Description

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).

Synopsis

class Ord a => Ix a where
- range :: (a, a) -> [a]
- index :: (a, a) -> a -> Int
- inRange :: (a, a) -> a -> Bool
- rangeSize :: (a, a) -> Int

The `Ix` class

class Ord a => Ix a where Source

The Ix class is used to map a contiguous subrange of values in a type onto integers. It is used primarily for array indexing (see the array package).

The first argument (l,u) of each of these operations is a pair specifying the lower and upper bounds of a contiguous subrange of values.

An implementation is entitled to assume the following laws about these operations:

inRange (l,u) i == elem i (range (l,u))
range (l,u) !! index (l,u) i == i, when inRange (l,u) i
map (index (l,u)) (range (l,u))) == [0..rangeSize (l,u)-1]
rangeSize (l,u) == length (range (l,u))

Minimal complete instance: range , index and inRange .

Minimal complete definition

range, inRange

Methods

range :: (a, a) -> [a] Source

The list of values in the subrange defined by a bounding pair.

index :: (a, a) -> a -> Int Source

The position of a subscript in the subrange.

inRange :: (a, a) -> a -> Bool Source

Returns True the given subscript lies in the range defined the bounding pair.

rangeSize :: (a, a) -> Int Source

The size of the subrange defined by a bounding pair.

Instances

Ix Bool

Ix Char

Ix Int

Ix Int8

Ix Int16

Ix Int32

Ix Int64

Ix Integer

Ix Ordering

Ix Word

Ix Word8

Ix Word16

Ix Word32

Ix Word64

Ix ()

Ix GeneralCategory

Ix SeekMode

Ix IOMode

(Ix a, Ix b) => Ix (a, b)

Ix (Proxy k s)

(Ix a1, Ix a2, Ix a3) => Ix (a1, a2, a3)

(Ix a1, Ix a2, Ix a3, Ix a4) => Ix (a1, a2, a3, a4)

(Ix a1, Ix a2, Ix a3, Ix a4, Ix a5) => Ix (a1, a2, a3, a4, a5)

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.

The Ix class

Deriving Instances of Ix

The `Ix` class

Deriving Instances of `Ix`