| Portability | portable |
|---|---|
| Stability | stable |
| Maintainer | libraries@haskell.org |
| Safe Haskell | Trustworthy |
Data.Ix
Contents
- The
Ixclass - 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:
Methods
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
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
Enumclass. 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.