Portability	portable
Stability	stable
Maintainer	libraries@haskell.org
Safe Haskell	Trustworthy

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

The `Ix` class

class Ord a => Ix a whereSource

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.

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 IOMode
Ix SeekMode
Ix GeneralCategory
(Ix a, Ix b) => Ix (a, b)
(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`