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<pre><a name="line-1"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Lava</span><span class='hs-varop'>.</span><span class='hs-conid'>Ref</span>
<a name="line-2"></a> <span class='hs-layout'>(</span> <span class='hs-conid'>Ref</span>
<a name="line-3"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>ref</span>
<a name="line-4"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>deref</span>
<a name="line-5"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>memoRef</span>
<a name="line-6"></a>
<a name="line-7"></a> <span class='hs-layout'>,</span> <span class='hs-conid'>TableIO</span>
<a name="line-8"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>tableIO</span>
<a name="line-9"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>extendIO</span>
<a name="line-10"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>findIO</span>
<a name="line-11"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>memoRefIO</span>
<a name="line-12"></a>
<a name="line-13"></a> <span class='hs-layout'>,</span> <span class='hs-conid'>TableST</span>
<a name="line-14"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>tableST</span>
<a name="line-15"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>extendST</span>
<a name="line-16"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>findST</span>
<a name="line-17"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>memoRefST</span>
<a name="line-18"></a> <span class='hs-layout'>)</span>
<a name="line-19"></a> <span class='hs-keyword'>where</span>
<a name="line-20"></a>
<a name="line-21"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Lava</span><span class='hs-varop'>.</span><span class='hs-conid'>MyST</span>
<a name="line-22"></a>
<a name="line-23"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>System</span><span class='hs-varop'>.</span><span class='hs-conid'>IO</span>
<a name="line-24"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>System</span><span class='hs-varop'>.</span><span class='hs-conid'>IO</span><span class='hs-varop'>.</span><span class='hs-conid'>Unsafe</span>
<a name="line-25"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>IORef</span>
<a name="line-26"></a>
<a name="line-27"></a><a name="unsafeCoerce"></a><span class='hs-definition'>unsafeCoerce</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>b</span>
<a name="line-28"></a><span class='hs-definition'>unsafeCoerce</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafePerformIO</span> <span class='hs-varop'>$</span>
<a name="line-29"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>writeIORef</span> <span class='hs-varid'>ref</span> <span class='hs-varid'>a</span>
<a name="line-30"></a> <span class='hs-varid'>readIORef</span> <span class='hs-varid'>ref</span>
<a name="line-31"></a> <span class='hs-keyword'>where</span>
<a name="line-32"></a> <span class='hs-varid'>ref</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafePerformIO</span> <span class='hs-varop'>$</span> <span class='hs-varid'>newIORef</span> <span class='hs-varid'>undefined</span>
<a name="line-33"></a> <span class='hs-comment'>-- Defined here because Unsafe.Coerce doesn't exist in Hugs.</span>
<a name="line-34"></a>
<a name="line-35"></a><span class='hs-comment'>{-
<a name="line-36"></a>
<a name="line-37"></a>Warning! One should regard this module as a portable
<a name="line-38"></a>extension to the Haskell language. It is not Haskell.
<a name="line-39"></a>
<a name="line-40"></a>-}</span>
<a name="line-41"></a>
<a name="line-42"></a><span class='hs-comment'>{-
<a name="line-43"></a>
<a name="line-44"></a>Here is how we implement Tables of Refs:
<a name="line-45"></a>
<a name="line-46"></a>A Table is nothing but a unique tag, of type TableTag.
<a name="line-47"></a>TableTag can be anything, as long as it is easy
<a name="line-48"></a>to create new ones, and we can compare them for
<a name="line-49"></a>equality. (I chose IORef ()).
<a name="line-50"></a>
<a name="line-51"></a>So how do we store Refs in a Table? We do not
<a name="line-52"></a>want the Tables keeping track of their Refs
<a name="line-53"></a>(which would be disastrous when the table
<a name="line-54"></a>becomes big, and we would not have any garbage
<a name="line-55"></a>collection).
<a name="line-56"></a>
<a name="line-57"></a>Instead, every Ref keeps track of the value it
<a name="line-58"></a>has in each table it is in. This has the advantage
<a name="line-59"></a>that we have a constant lookup time (if the number of
<a name="line-60"></a>Tables we are using is small), and we get garbage
<a name="line-61"></a>collection of table entries for free.
<a name="line-62"></a>
<a name="line-63"></a>The disadvantage is that, since the types of the
<a name="line-64"></a>Tables vary, the Ref has no idea what type of
<a name="line-65"></a>values it is supposed to store. So we use dynamic
<a name="line-66"></a>types.
<a name="line-67"></a>
<a name="line-68"></a>A Ref is implemented as follows: it has two pieces
<a name="line-69"></a>of information. The first one is an updatable
<a name="line-70"></a>list of entries for each table it is a member in.
<a name="line-71"></a>Since it is an updatable list, it is an IORef, which
<a name="line-72"></a>we also use to compare two Refs. The second part is
<a name="line-73"></a>just the value the Ref is pointing at (this can never
<a name="line-74"></a>change anyway).
<a name="line-75"></a>
<a name="line-76"></a>-}</span>
<a name="line-77"></a>
<a name="line-78"></a><span class='hs-comment'>-----------------------------------------------------------------</span>
<a name="line-79"></a><span class='hs-comment'>-- Ref</span>
<a name="line-80"></a>
<a name="line-81"></a><a name="Ref"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>Ref</span> <span class='hs-varid'>a</span>
<a name="line-82"></a> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Ref</span> <span class='hs-layout'>(</span><span class='hs-conid'>IORef</span> <span class='hs-keyglyph'>[</span><span class='hs-layout'>(</span><span class='hs-conid'>TableTag</span><span class='hs-layout'>,</span> <span class='hs-conid'>Dyn</span><span class='hs-layout'>)</span><span class='hs-keyglyph'>]</span><span class='hs-layout'>)</span> <span class='hs-varid'>a</span>
<a name="line-83"></a>
<a name="line-84"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Eq</span> <span class='hs-layout'>(</span><span class='hs-conid'>Ref</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-85"></a> <span class='hs-conid'>Ref</span> <span class='hs-varid'>r1</span> <span class='hs-keyword'>_</span> <span class='hs-varop'>==</span> <span class='hs-conid'>Ref</span> <span class='hs-varid'>r2</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>r1</span> <span class='hs-varop'>==</span> <span class='hs-varid'>r2</span>
<a name="line-86"></a>
<a name="line-87"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Show</span> <span class='hs-layout'>(</span><span class='hs-conid'>Ref</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-88"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>Ref</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showChar</span> <span class='hs-chr'>'{'</span> <span class='hs-varop'>.</span> <span class='hs-varid'>shows</span> <span class='hs-varid'>a</span> <span class='hs-varop'>.</span> <span class='hs-varid'>showChar</span> <span class='hs-chr'>'}'</span>
<a name="line-89"></a>
<a name="line-90"></a><a name="ref"></a><span class='hs-definition'>ref</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Ref</span> <span class='hs-varid'>a</span>
<a name="line-91"></a><span class='hs-definition'>ref</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafePerformIO</span> <span class='hs-varop'>$</span>
<a name="line-92"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>r</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newIORef</span> <span class='hs-conid'>[]</span>
<a name="line-93"></a> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-conid'>Ref</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-94"></a>
<a name="line-95"></a><a name="deref"></a><span class='hs-definition'>deref</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Ref</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span>
<a name="line-96"></a><span class='hs-definition'>deref</span> <span class='hs-layout'>(</span><span class='hs-conid'>Ref</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>a</span>
<a name="line-97"></a>
<a name="line-98"></a><span class='hs-comment'>-----------------------------------------------------------------</span>
<a name="line-99"></a><span class='hs-comment'>-- Table IO</span>
<a name="line-100"></a>
<a name="line-101"></a><a name="TableTag"></a><span class='hs-keyword'>type</span> <span class='hs-conid'>TableTag</span>
<a name="line-102"></a> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>IORef</span> <span class='hs-conid'>()</span>
<a name="line-103"></a>
<a name="line-104"></a><a name="TableIO"></a><span class='hs-keyword'>newtype</span> <span class='hs-conid'>TableIO</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span>
<a name="line-105"></a> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>TableIO</span> <span class='hs-conid'>TableTag</span>
<a name="line-106"></a> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Eq</span>
<a name="line-107"></a>
<a name="line-108"></a><a name="tableIO"></a><span class='hs-definition'>tableIO</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IO</span> <span class='hs-layout'>(</span><span class='hs-conid'>TableIO</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span>
<a name="line-109"></a><span class='hs-definition'>tableIO</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>TableIO</span> <span class='hs-varop'>`fmap`</span> <span class='hs-varid'>newIORef</span> <span class='hs-conid'>()</span>
<a name="line-110"></a>
<a name="line-111"></a><a name="findIO"></a><span class='hs-definition'>findIO</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>TableIO</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Ref</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-layout'>(</span><span class='hs-conid'>Maybe</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span>
<a name="line-112"></a><span class='hs-definition'>findIO</span> <span class='hs-layout'>(</span><span class='hs-conid'>TableIO</span> <span class='hs-varid'>t</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Ref</span> <span class='hs-varid'>r</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-113"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>list</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>readIORef</span> <span class='hs-varid'>r</span>
<a name="line-114"></a> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-varid'>fromDyn</span> <span class='hs-varop'>`fmap`</span> <span class='hs-varid'>lookup</span> <span class='hs-varid'>t</span> <span class='hs-varid'>list</span><span class='hs-layout'>)</span>
<a name="line-115"></a>
<a name="line-116"></a><a name="extendIO"></a><span class='hs-definition'>extendIO</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>TableIO</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Ref</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span>
<a name="line-117"></a><span class='hs-definition'>extendIO</span> <span class='hs-layout'>(</span><span class='hs-conid'>TableIO</span> <span class='hs-varid'>t</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Ref</span> <span class='hs-varid'>r</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>=</span>
<a name="line-118"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>list</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>readIORef</span> <span class='hs-varid'>r</span>
<a name="line-119"></a> <span class='hs-varid'>writeIORef</span> <span class='hs-varid'>r</span> <span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-varid'>t</span><span class='hs-layout'>,</span><span class='hs-varid'>toDyn</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-conop'>:</span> <span class='hs-varid'>filter</span> <span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-varop'>/=</span> <span class='hs-varid'>t</span><span class='hs-layout'>)</span> <span class='hs-varop'>.</span> <span class='hs-varid'>fst</span><span class='hs-layout'>)</span> <span class='hs-varid'>list</span><span class='hs-layout'>)</span>
<a name="line-120"></a>
<a name="line-121"></a><span class='hs-comment'>-----------------------------------------------------------------</span>
<a name="line-122"></a><span class='hs-comment'>-- Table ST</span>
<a name="line-123"></a>
<a name="line-124"></a><a name="TableST"></a><span class='hs-keyword'>newtype</span> <span class='hs-conid'>TableST</span> <span class='hs-varid'>s</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span>
<a name="line-125"></a> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>TableST</span> <span class='hs-layout'>(</span><span class='hs-conid'>TableIO</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span>
<a name="line-126"></a> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Eq</span>
<a name="line-127"></a>
<a name="line-128"></a><a name="tableST"></a><span class='hs-definition'>tableST</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ST</span> <span class='hs-varid'>s</span> <span class='hs-layout'>(</span><span class='hs-conid'>TableST</span> <span class='hs-varid'>s</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span>
<a name="line-129"></a><span class='hs-definition'>tableST</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafeIOtoST</span> <span class='hs-layout'>(</span><span class='hs-conid'>TableST</span> <span class='hs-varop'>`fmap`</span> <span class='hs-varid'>tableIO</span><span class='hs-layout'>)</span>
<a name="line-130"></a>
<a name="line-131"></a><a name="findST"></a><span class='hs-definition'>findST</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>TableST</span> <span class='hs-varid'>s</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Ref</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ST</span> <span class='hs-varid'>s</span> <span class='hs-layout'>(</span><span class='hs-conid'>Maybe</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span>
<a name="line-132"></a><span class='hs-definition'>findST</span> <span class='hs-layout'>(</span><span class='hs-conid'>TableST</span> <span class='hs-varid'>tab</span><span class='hs-layout'>)</span> <span class='hs-varid'>r</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafeIOtoST</span> <span class='hs-layout'>(</span><span class='hs-varid'>findIO</span> <span class='hs-varid'>tab</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span>
<a name="line-133"></a>
<a name="line-134"></a><a name="extendST"></a><span class='hs-definition'>extendST</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>TableST</span> <span class='hs-varid'>s</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Ref</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ST</span> <span class='hs-varid'>s</span> <span class='hs-conid'>()</span>
<a name="line-135"></a><span class='hs-definition'>extendST</span> <span class='hs-layout'>(</span><span class='hs-conid'>TableST</span> <span class='hs-varid'>tab</span><span class='hs-layout'>)</span> <span class='hs-varid'>r</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafeIOtoST</span> <span class='hs-layout'>(</span><span class='hs-varid'>extendIO</span> <span class='hs-varid'>tab</span> <span class='hs-varid'>r</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span>
<a name="line-136"></a>
<a name="line-137"></a><span class='hs-comment'>-----------------------------------------------------------------</span>
<a name="line-138"></a><span class='hs-comment'>-- Memo</span>
<a name="line-139"></a>
<a name="line-140"></a><a name="memoRef"></a><span class='hs-definition'>memoRef</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Ref</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-conid'>Ref</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span>
<a name="line-141"></a><span class='hs-definition'>memoRef</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafePerformIO</span> <span class='hs-varop'>.</span> <span class='hs-varid'>memoRefIO</span> <span class='hs-layout'>(</span><span class='hs-varid'>return</span> <span class='hs-varop'>.</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span>
<a name="line-142"></a>
<a name="line-143"></a><a name="memoRefIO"></a><span class='hs-definition'>memoRefIO</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Ref</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-conid'>Ref</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span>
<a name="line-144"></a><span class='hs-definition'>memoRefIO</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafePerformIO</span> <span class='hs-varop'>$</span>
<a name="line-145"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>tab</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>tableIO</span>
<a name="line-146"></a> <span class='hs-keyword'>let</span> <span class='hs-varid'>f'</span> <span class='hs-varid'>r</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span> <span class='hs-varid'>mb</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>findIO</span> <span class='hs-varid'>tab</span> <span class='hs-varid'>r</span>
<a name="line-147"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>mb</span> <span class='hs-keyword'>of</span>
<a name="line-148"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>do</span> <span class='hs-varid'>return</span> <span class='hs-varid'>b</span>
<a name="line-149"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>fixIO</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span>
<a name="line-150"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>extendIO</span> <span class='hs-varid'>tab</span> <span class='hs-varid'>r</span> <span class='hs-varid'>b</span>
<a name="line-151"></a> <span class='hs-varid'>f</span> <span class='hs-varid'>r</span>
<a name="line-152"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>f'</span>
<a name="line-153"></a>
<a name="line-154"></a><a name="memoRefST"></a><span class='hs-definition'>memoRefST</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Ref</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ST</span> <span class='hs-varid'>s</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-conid'>Ref</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ST</span> <span class='hs-varid'>s</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span>
<a name="line-155"></a><span class='hs-definition'>memoRefST</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafePerformST</span> <span class='hs-varop'>$</span>
<a name="line-156"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>tab</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>tableST</span>
<a name="line-157"></a> <span class='hs-keyword'>let</span> <span class='hs-varid'>f'</span> <span class='hs-varid'>r</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span> <span class='hs-varid'>mb</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>findST</span> <span class='hs-varid'>tab</span> <span class='hs-varid'>r</span>
<a name="line-158"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>mb</span> <span class='hs-keyword'>of</span>
<a name="line-159"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>do</span> <span class='hs-varid'>return</span> <span class='hs-varid'>b</span>
<a name="line-160"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>fixST</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span>
<a name="line-161"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>extendST</span> <span class='hs-varid'>tab</span> <span class='hs-varid'>r</span> <span class='hs-varid'>b</span>
<a name="line-162"></a> <span class='hs-varid'>f</span> <span class='hs-varid'>r</span>
<a name="line-163"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>f'</span>
<a name="line-164"></a>
<a name="line-165"></a><span class='hs-comment'>-----------------------------------------------------------------</span>
<a name="line-166"></a><span class='hs-comment'>-- Dyn</span>
<a name="line-167"></a>
<a name="line-168"></a><a name="Dyn"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>Dyn</span>
<a name="line-169"></a> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Dyn</span>
<a name="line-170"></a>
<a name="line-171"></a><a name="toDyn"></a><span class='hs-definition'>toDyn</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Dyn</span>
<a name="line-172"></a><span class='hs-definition'>toDyn</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafeCoerce</span>
<a name="line-173"></a>
<a name="line-174"></a><a name="fromDyn"></a><span class='hs-definition'>fromDyn</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Dyn</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span>
<a name="line-175"></a><span class='hs-definition'>fromDyn</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafeCoerce</span>
<a name="line-176"></a>
<a name="line-177"></a><span class='hs-comment'>-----------------------------------------------------------------</span>
<a name="line-178"></a><span class='hs-comment'>-- the end.</span>
<a name="line-179"></a>
<a name="line-180"></a>
<a name="line-181"></a>
</pre></body>
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