<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html> <head> <!-- Generated by HsColour, http://www.cs.york.ac.uk/fp/darcs/hscolour/ --> <title>Data/Array/ST.hs</title> <link type='text/css' rel='stylesheet' href='hscolour.css' /> </head> <body> <pre><a name="line-1"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span> <a name="line-2"></a><span class='hs-comment'>-- |</span> <a name="line-3"></a><span class='hs-comment'>-- Module : Data.Array.ST</span> <a name="line-4"></a><span class='hs-comment'>-- Copyright : (c) The University of Glasgow 2001</span> <a name="line-5"></a><span class='hs-comment'>-- License : BSD-style (see the file libraries/base/LICENSE)</span> <a name="line-6"></a><span class='hs-comment'>-- </span> <a name="line-7"></a><span class='hs-comment'>-- Maintainer : libraries@haskell.org</span> <a name="line-8"></a><span class='hs-comment'>-- Stability : experimental</span> <a name="line-9"></a><span class='hs-comment'>-- Portability : non-portable (uses Data.Array.MArray)</span> <a name="line-10"></a><span class='hs-comment'>--</span> <a name="line-11"></a><span class='hs-comment'>-- Mutable boxed and unboxed arrays in the 'Control.Monad.ST.ST' monad.</span> <a name="line-12"></a><span class='hs-comment'>--</span> <a name="line-13"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span> <a name="line-14"></a> <a name="line-15"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Array</span><span class='hs-varop'>.</span><span class='hs-conid'>ST</span> <span class='hs-layout'>(</span> <a name="line-16"></a> <a name="line-17"></a> <span class='hs-comment'>-- * Boxed arrays</span> <a name="line-18"></a> <span class='hs-conid'>STArray</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- instance of: Eq, MArray</span> <a name="line-19"></a> <span class='hs-varid'>runSTArray</span><span class='hs-layout'>,</span> <a name="line-20"></a> <a name="line-21"></a> <span class='hs-comment'>-- * Unboxed arrays</span> <a name="line-22"></a> <span class='hs-conid'>STUArray</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- instance of: Eq, MArray</span> <a name="line-23"></a> <span class='hs-varid'>runSTUArray</span><span class='hs-layout'>,</span> <a name="line-24"></a> <span class='hs-varid'>castSTUArray</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: STUArray s i a -> ST s (STUArray s i b)</span> <a name="line-25"></a> <a name="line-26"></a> <span class='hs-comment'>-- * Overloaded mutable array interface</span> <a name="line-27"></a> <span class='hs-keyword'>module</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Array</span><span class='hs-varop'>.</span><span class='hs-conid'>MArray</span><span class='hs-layout'>,</span> <a name="line-28"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span> <a name="line-29"></a> <a name="line-30"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Array</span><span class='hs-varop'>.</span><span class='hs-conid'>MArray</span> <a name="line-31"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Array</span><span class='hs-varop'>.</span><span class='hs-conid'>Base</span> <span class='hs-layout'>(</span> <span class='hs-conid'>STUArray</span><span class='hs-layout'>,</span> <span class='hs-varid'>castSTUArray</span><span class='hs-layout'>,</span> <span class='hs-conid'>UArray</span><span class='hs-layout'>,</span> <span class='hs-varid'>unsafeFreezeSTUArray</span> <span class='hs-layout'>)</span> <a name="line-32"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>ST</span> <span class='hs-layout'>(</span> <span class='hs-conid'>ST</span><span class='hs-layout'>,</span> <span class='hs-varid'>runST</span> <span class='hs-layout'>)</span> <a name="line-33"></a> <a name="line-34"></a><span class='hs-cpp'>#ifdef __HUGS__</span> <a name="line-35"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Hugs</span><span class='hs-varop'>.</span><span class='hs-conid'>Array</span> <span class='hs-layout'>(</span> <span class='hs-conid'>Array</span> <span class='hs-layout'>)</span> <a name="line-36"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Hugs</span><span class='hs-varop'>.</span><span class='hs-conid'>ST</span> <span class='hs-layout'>(</span> <span class='hs-conid'>STArray</span><span class='hs-layout'>,</span> <span class='hs-varid'>unsafeFreezeSTArray</span> <span class='hs-layout'>)</span> <a name="line-37"></a><span class='hs-cpp'>#endif</span> <a name="line-38"></a> <a name="line-39"></a><span class='hs-cpp'>#ifdef __GLASGOW_HASKELL__</span> <a name="line-40"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>Arr</span> <span class='hs-layout'>(</span> <span class='hs-conid'>STArray</span><span class='hs-layout'>,</span> <span class='hs-conid'>Array</span><span class='hs-layout'>,</span> <span class='hs-varid'>unsafeFreezeSTArray</span> <span class='hs-layout'>)</span> <a name="line-41"></a><span class='hs-cpp'>#endif</span> <a name="line-42"></a> <a name="line-43"></a><a name="runSTArray"></a><span class='hs-comment'>-- | A safe way to create and work with a mutable array before returning an</span> <a name="line-44"></a><span class='hs-comment'>-- immutable array for later perusal. This function avoids copying</span> <a name="line-45"></a><span class='hs-comment'>-- the array before returning it - it uses 'unsafeFreeze' internally, but</span> <a name="line-46"></a><span class='hs-comment'>-- this wrapper is a safe interface to that function.</span> <a name="line-47"></a><span class='hs-comment'>--</span> <a name="line-48"></a><span class='hs-definition'>runSTArray</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Ix</span> <span class='hs-varid'>i</span><span class='hs-layout'>)</span> <a name="line-49"></a> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-keyword'>forall</span> <span class='hs-varid'>s</span> <span class='hs-varop'>.</span> <span class='hs-conid'>ST</span> <span class='hs-varid'>s</span> <span class='hs-layout'>(</span><span class='hs-conid'>STArray</span> <span class='hs-varid'>s</span> <span class='hs-varid'>i</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <a name="line-50"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Array</span> <span class='hs-varid'>i</span> <span class='hs-varid'>e</span> <a name="line-51"></a><span class='hs-definition'>runSTArray</span> <span class='hs-varid'>st</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>runST</span> <span class='hs-layout'>(</span><span class='hs-varid'>st</span> <span class='hs-varop'>>>=</span> <span class='hs-varid'>unsafeFreezeSTArray</span><span class='hs-layout'>)</span> <a name="line-52"></a> <a name="line-53"></a><a name="runSTUArray"></a><span class='hs-comment'>-- | A safe way to create and work with an unboxed mutable array before</span> <a name="line-54"></a><span class='hs-comment'>-- returning an immutable array for later perusal. This function</span> <a name="line-55"></a><span class='hs-comment'>-- avoids copying the array before returning it - it uses</span> <a name="line-56"></a><span class='hs-comment'>-- 'unsafeFreeze' internally, but this wrapper is a safe interface to</span> <a name="line-57"></a><span class='hs-comment'>-- that function.</span> <a name="line-58"></a><span class='hs-comment'>--</span> <a name="line-59"></a><span class='hs-definition'>runSTUArray</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Ix</span> <span class='hs-varid'>i</span><span class='hs-layout'>)</span> <a name="line-60"></a> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-keyword'>forall</span> <span class='hs-varid'>s</span> <span class='hs-varop'>.</span> <span class='hs-conid'>ST</span> <span class='hs-varid'>s</span> <span class='hs-layout'>(</span><span class='hs-conid'>STUArray</span> <span class='hs-varid'>s</span> <span class='hs-varid'>i</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <a name="line-61"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>UArray</span> <span class='hs-varid'>i</span> <span class='hs-varid'>e</span> <a name="line-62"></a><span class='hs-definition'>runSTUArray</span> <span class='hs-varid'>st</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>runST</span> <span class='hs-layout'>(</span><span class='hs-varid'>st</span> <span class='hs-varop'>>>=</span> <span class='hs-varid'>unsafeFreezeSTUArray</span><span class='hs-layout'>)</span> <a name="line-63"></a> <a name="line-64"></a> <a name="line-65"></a><span class='hs-comment'>-- INTERESTING... this is the type we'd like to give to runSTUArray:</span> <a name="line-66"></a><span class='hs-comment'>--</span> <a name="line-67"></a><span class='hs-comment'>-- runSTUArray :: (Ix i, IArray UArray e, </span> <a name="line-68"></a><span class='hs-comment'>-- forall s. MArray (STUArray s) e (ST s))</span> <a name="line-69"></a><span class='hs-comment'>-- => (forall s . ST s (STUArray s i e))</span> <a name="line-70"></a><span class='hs-comment'>-- -> UArray i e</span> <a name="line-71"></a><span class='hs-comment'>--</span> <a name="line-72"></a><span class='hs-comment'>-- Note the quantified constraint. We dodged the problem by using</span> <a name="line-73"></a><span class='hs-comment'>-- unsafeFreezeSTUArray directly in the defn of runSTUArray above, but</span> <a name="line-74"></a><span class='hs-comment'>-- this essentially constrains us to a single unsafeFreeze for all STUArrays</span> <a name="line-75"></a><span class='hs-comment'>-- (in theory we might have a different one for certain element types).</span> </pre></body> </html>
