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<pre><a name="line-1"></a><span class='hs-comment'>{-# OPTIONS_GHC -XNoImplicitPrelude #-}</span>
<a name="line-2"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-3"></a><span class='hs-comment'>-- |</span>
<a name="line-4"></a><span class='hs-comment'>-- Module : Data.Word</span>
<a name="line-5"></a><span class='hs-comment'>-- Copyright : (c) The University of Glasgow 2001</span>
<a name="line-6"></a><span class='hs-comment'>-- License : BSD-style (see the file libraries/base/LICENSE)</span>
<a name="line-7"></a><span class='hs-comment'>-- </span>
<a name="line-8"></a><span class='hs-comment'>-- Maintainer : libraries@haskell.org</span>
<a name="line-9"></a><span class='hs-comment'>-- Stability : experimental</span>
<a name="line-10"></a><span class='hs-comment'>-- Portability : portable</span>
<a name="line-11"></a><span class='hs-comment'>--</span>
<a name="line-12"></a><span class='hs-comment'>-- Unsigned integer types.</span>
<a name="line-13"></a><span class='hs-comment'>--</span>
<a name="line-14"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-15"></a>
<a name="line-16"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Word</span>
<a name="line-17"></a> <span class='hs-layout'>(</span>
<a name="line-18"></a> <span class='hs-comment'>-- * Unsigned integral types</span>
<a name="line-19"></a>
<a name="line-20"></a> <span class='hs-conid'>Word</span><span class='hs-layout'>,</span>
<a name="line-21"></a> <span class='hs-conid'>Word8</span><span class='hs-layout'>,</span> <span class='hs-conid'>Word16</span><span class='hs-layout'>,</span> <span class='hs-conid'>Word32</span><span class='hs-layout'>,</span> <span class='hs-conid'>Word64</span><span class='hs-layout'>,</span>
<a name="line-22"></a>
<a name="line-23"></a> <span class='hs-comment'>-- * Notes</span>
<a name="line-24"></a>
<a name="line-25"></a> <span class='hs-comment'>-- $notes</span>
<a name="line-26"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-27"></a>
<a name="line-28"></a><span class='hs-cpp'>#ifdef __GLASGOW_HASKELL__</span>
<a name="line-29"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>Word</span>
<a name="line-30"></a><span class='hs-cpp'>#endif</span>
<a name="line-31"></a>
<a name="line-32"></a><span class='hs-cpp'>#ifdef __HUGS__</span>
<a name="line-33"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Hugs</span><span class='hs-varop'>.</span><span class='hs-conid'>Word</span>
<a name="line-34"></a><span class='hs-cpp'>#endif</span>
<a name="line-35"></a>
<a name="line-36"></a><span class='hs-cpp'>#ifdef __NHC__</span>
<a name="line-37"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>NHC</span><span class='hs-varop'>.</span><span class='hs-conid'>FFI</span> <span class='hs-layout'>(</span><span class='hs-conid'>Word8</span><span class='hs-layout'>,</span> <span class='hs-conid'>Word16</span><span class='hs-layout'>,</span> <span class='hs-conid'>Word32</span><span class='hs-layout'>,</span> <span class='hs-conid'>Word64</span><span class='hs-layout'>)</span>
<a name="line-38"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>NHC</span><span class='hs-varop'>.</span><span class='hs-conid'>SizedTypes</span> <span class='hs-layout'>(</span><span class='hs-conid'>Word8</span><span class='hs-layout'>,</span> <span class='hs-conid'>Word16</span><span class='hs-layout'>,</span> <span class='hs-conid'>Word32</span><span class='hs-layout'>,</span> <span class='hs-conid'>Word64</span><span class='hs-layout'>)</span> <span class='hs-comment'>-- instances of Bits</span>
<a name="line-39"></a><a name="Word"></a><span class='hs-keyword'>type</span> <span class='hs-conid'>Word</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Word32</span>
<a name="line-40"></a><span class='hs-cpp'>#endif</span>
<a name="line-41"></a>
<a name="line-42"></a><span class='hs-comment'>{- $notes
<a name="line-43"></a>
<a name="line-44"></a>* All arithmetic is performed modulo 2^n, where n is the number of
<a name="line-45"></a> bits in the type. One non-obvious consequence of this is that 'Prelude.negate'
<a name="line-46"></a> should /not/ raise an error on negative arguments.
<a name="line-47"></a>
<a name="line-48"></a>* For coercing between any two integer types, use
<a name="line-49"></a> 'Prelude.fromIntegral', which is specialized for all the
<a name="line-50"></a> common cases so should be fast enough. Coercing word types to and
<a name="line-51"></a> from integer types preserves representation, not sign.
<a name="line-52"></a>
<a name="line-53"></a>* It would be very natural to add a type @Natural@ providing an unbounded
<a name="line-54"></a> size unsigned integer, just as 'Prelude.Integer' provides unbounded
<a name="line-55"></a> size signed integers. We do not do that yet since there is no demand
<a name="line-56"></a> for it.
<a name="line-57"></a>
<a name="line-58"></a>* The rules that hold for 'Prelude.Enum' instances over a bounded type
<a name="line-59"></a> such as 'Prelude.Int' (see the section of the Haskell report dealing
<a name="line-60"></a> with arithmetic sequences) also hold for the 'Prelude.Enum' instances
<a name="line-61"></a> over the various 'Word' types defined here.
<a name="line-62"></a>
<a name="line-63"></a>* Right and left shifts by amounts greater than or equal to the width
<a name="line-64"></a> of the type result in a zero result. This is contrary to the
<a name="line-65"></a> behaviour in C, which is undefined; a common interpretation is to
<a name="line-66"></a> truncate the shift count to the width of the type, for example @1 \<\<
<a name="line-67"></a> 32 == 1@ in some C implementations.
<a name="line-68"></a>-}</span>
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