| base-3.0.2.0: Basic libraries | Source code | 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 | Source

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

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

data Word8 | Source

8-bit unsigned integer type
Instances

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

data Word16 | Source

16-bit unsigned integer type
Instances

Bits Word16
Bounded Word16
Data Word16
Enum Word16
Eq Word16
Integral Word16
Ix Word16
Num Word16
Ord Word16
PrintfArg Word16
Read Word16
Real Word16
Show Word16
Storable Word16
Typeable Word16

data Word32 | Source

32-bit unsigned integer type
Instances

Bits Word32
Bounded Word32
Data Word32
Enum Word32
Eq Word32
Integral Word32
Ix Word32
Num Word32
Ord Word32
PrintfArg Word32
Read Word32
Real Word32
Show Word32
Storable Word32
Typeable Word32

data Word64 | Source

64-bit unsigned integer type
Instances

Bits Word64
Bounded Word64
Data Word64
Enum Word64
Eq Word64
Integral Word64
Ix Word64
Num Word64
Ord Word64
PrintfArg Word64
Read Word64
Real Word64
Show Word64
Storable Word64
Typeable 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 `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.

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