1 {-# OPTIONS -fno-implicit-prelude #-}

2 -----------------------------------------------------------------------------

3 -- |

4 -- Module : Data.Word

5 -- Copyright : (c) The University of Glasgow 2001

6 -- License : BSD-style (see the file libraries/base/LICENSE)

7 --

8 -- Maintainer : libraries@haskell.org

9 -- Stability : experimental

10 -- Portability : portable

11 --

12 -- Unsigned integer types.

13 --

14 -----------------------------------------------------------------------------

17 (

18 -- * Unsigned integral types

20 Word,

23 -- * Notes

25 -- $notes

28 #ifdef __GLASGOW_HASKELL__

30 #endif

32 #ifdef __HUGS__

34 #endif

36 {- $notes

38 * All arithmetic is performed modulo 2^n, where n is the number of

39 bits in the type. One non-obvious consequence of this is that 'negate'

40 should /not/ raise an error on negative arguments.

42 * For coercing between any two integer types, use

43 'fromIntegral', which is specialized for all the

44 common cases so should be fast enough. Coercing word types to and

45 from integer types preserves representation, not sign.

47 * It would be very natural to add a type 'Natural' providing an unbounded

48 size unsigned integer, just as 'Integer' provides unbounded

49 size signed integers. We do not do that yet since there is no demand

50 for it.

52 * The rules that hold for 'Enum' instances over a bounded type

53 such as 'Int' (see the section of the Haskell report dealing

54 with arithmetic sequences) also hold for the 'Enum' instances

55 over the various 'Word' types defined here.

57 * Right and left shifts by amounts greater than or equal to the width

58 of the type result in a zero result. This is contrary to the

59 behaviour in C, which is undefined; a common interpretation is to

60 truncate the shift count to the width of the type, for example @1 \<\<

61 32 == 1@ in some C implementations.

62 -}