base-4.5.0.0: Basic libraries

Data.Word

Contents

Description

Unsigned integer types.

Synopsis

# Unsigned integral types

data Word Source

A `Word` is an unsigned integral type, with the same size as `Int`.

Instances

 Bounded Word Enum Word Eq Word Integral Word Data Word Num Word Ord Word Read Word Real Word Show Word Ix Word Typeable Word Bits Word Storable Word PrintfArg Word

data Word8 Source

8-bit unsigned integer type

Instances

 Bounded Word8 Enum Word8 Eq Word8 Integral Word8 Data Word8 Num Word8 Ord Word8 Read Word8 Real Word8 Show Word8 Ix Word8 Typeable Word8 Bits Word8 Storable Word8 PrintfArg Word8

data Word16 Source

16-bit unsigned integer type

data Word32 Source

32-bit unsigned integer type

data Word64 Source

64-bit unsigned integer type

# Notes

• All arithmetic is performed modulo 2^n, where n is the number of bits in the type. One non-obvious consequence of this is that `negate` should not raise an error on negative arguments.
• For coercing between any two integer types, use `fromIntegral`, which is specialized for all the common cases so should be fast enough. Coercing word types to and from integer types preserves representation, not sign.
• It would be very natural to add a type `Natural` providing an unbounded size unsigned integer, just as `Integer` provides unbounded size signed integers. We do not do that yet since there is no demand for it.
• The rules that hold for `Enum` instances over a bounded type such as `Int` (see the section of the Haskell report dealing with arithmetic sequences) also hold for the `Enum` instances over the various `Word` types defined here.
• Right and left shifts by amounts greater than or equal to the width of the type result in a zero result. This is contrary to the behaviour in C, which is undefined; a common interpretation is to truncate the shift count to the width of the type, for example ```1 << 32 == 1``` in some C implementations.