|Copyright||(c) The University of Glasgow 2001|
|License||BSD-style (see the file libraries/base/LICENSE)|
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:
The list of values in the subrange defined by a bounding pair.
The position of a subscript in the subrange.
True the given subscript lies in the range defined
the bounding pair.
The size of the subrange defined by a bounding pair.
|(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
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
- 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 chapter 19, section 2 of the Haskell 2010 report: https://www.haskell.org/onlinereport/haskell2010/haskellch19.html.