base-4.0.0.0: Basic libraries Contents Index

Data.Word Portability portable Stability experimental Maintainer libraries@haskell.org

Contents Unsigned integral types Notes

Description

Unsigned integer types.

Synopsis

data Word data Word8 data Word16 data Word32 data Word64

Unsigned integral types

data Word

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

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 Storable Word8 PrintfArg Word8

data Word16

16-bit unsigned integer type Instances Bounded Word16 Enum Word16 Eq Word16 Integral Word16 Data Word16 Num Word16 Ord Word16 Read Word16 Real Word16 Show Word16 Ix Word16 Typeable Word16 Bits Word16 Storable Word16 Storable Word16 PrintfArg Word16

data Word32

32-bit unsigned integer type Instances Bounded Word32 Enum Word32 Eq Word32 Integral Word32 Data Word32 Num Word32 Ord Word32 Read Word32 Real Word32 Show Word32 Ix Word32 Typeable Word32 Bits Word32 Storable Word32 Storable Word32 PrintfArg Word32

data Word64

64-bit unsigned integer type Instances Bounded Word64 Enum Word64 Eq Word64 Integral Word64 Data Word64 Num Word64 Ord Word64 Read Word64 Real Word64 Show Word64 Ix Word64 Typeable Word64 Bits Word64 Storable Word64 Storable Word64 PrintfArg Word64

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 Prelude.negate should not raise an error on negative arguments. For coercing between any two integer types, use Prelude.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 Prelude.Integer provides unbounded size signed integers. We do not do that yet since there is no demand for it. The rules that hold for Prelude.Enum instances over a bounded type such as Prelude.Int (see the section of the Haskell report dealing with arithmetic sequences) also hold for the Prelude.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.

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