<?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>Lava/Sequential.hs</title> <link type='text/css' rel='stylesheet' href='hscolour.css' /> </head> <body> <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'>Sequential</span> <a name="line-2"></a> <span class='hs-layout'>(</span> <span class='hs-varid'>simulateSeq</span> <a name="line-3"></a> <span class='hs-layout'>)</span> <a name="line-4"></a> <span class='hs-keyword'>where</span> <a name="line-5"></a> <a name="line-6"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Lava</span><span class='hs-varop'>.</span><span class='hs-conid'>Ref</span> <a name="line-7"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Lava</span><span class='hs-varop'>.</span><span class='hs-conid'>Signal</span> <a name="line-8"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Lava</span><span class='hs-varop'>.</span><span class='hs-conid'>Netlist</span> <a name="line-9"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Lava</span><span class='hs-varop'>.</span><span class='hs-conid'>Sequent</span> <a name="line-10"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Lava</span><span class='hs-varop'>.</span><span class='hs-conid'>Generic</span> <a name="line-11"></a> <a name="line-12"></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-13"></a> <span class='hs-layout'>(</span> <span class='hs-conid'>ST</span> <a name="line-14"></a> <span class='hs-layout'>,</span> <span class='hs-conid'>STRef</span> <a name="line-15"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>newSTRef</span> <a name="line-16"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>readSTRef</span> <a name="line-17"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>writeSTRef</span> <a name="line-18"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>unsafeInterleaveST</span> <a name="line-19"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>runST</span> <a name="line-20"></a> <span class='hs-layout'>)</span> <a name="line-21"></a> <a name="line-22"></a><span class='hs-comment'>----------------------------------------------------------------</span> <a name="line-23"></a><span class='hs-comment'>-- wire datatype</span> <a name="line-24"></a> <a name="line-25"></a><a name="Var"></a><span class='hs-keyword'>type</span> <span class='hs-conid'>Var</span> <span class='hs-varid'>s</span> <a name="line-26"></a> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-conid'>STRef</span> <span class='hs-varid'>s</span> <span class='hs-layout'>(</span><span class='hs-conid'>S</span> <span class='hs-conid'>Symbol</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-conid'>STRef</span> <span class='hs-varid'>s</span> <span class='hs-layout'>(</span><span class='hs-conid'>Wire</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <a name="line-27"></a> <a name="line-28"></a><a name="Wire"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>Wire</span> <span class='hs-varid'>s</span> <a name="line-29"></a> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Wire</span> <a name="line-30"></a> <span class='hs-layout'>{</span> <span class='hs-varid'>dependencies</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Var</span> <span class='hs-varid'>s</span><span class='hs-keyglyph'>]</span> <a name="line-31"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>kick</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-32"></a> <span class='hs-layout'>}</span> <a name="line-33"></a> <a name="line-34"></a><span class='hs-comment'>----------------------------------------------------------------</span> <a name="line-35"></a><span class='hs-comment'>-- simulate</span> <a name="line-36"></a> <a name="line-37"></a><a name="simulateSeq"></a><span class='hs-definition'>simulateSeq</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Generic</span> <span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-conid'>Generic</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-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-keyglyph'>[</span><span class='hs-varid'>a</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>b</span><span class='hs-keyglyph'>]</span> <a name="line-38"></a><span class='hs-definition'>simulateSeq</span> <span class='hs-varid'>circ</span> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>[]</span> <a name="line-39"></a><span class='hs-definition'>simulateSeq</span> <span class='hs-varid'>circ</span> <span class='hs-varid'>inps</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>runST</span> <span class='hs-layout'>(</span> <a name="line-40"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>roots</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newSTRef</span> <span class='hs-conid'>[]</span> <a name="line-41"></a> <a name="line-42"></a> <span class='hs-keyword'>let</span> <span class='hs-varid'>root</span> <span class='hs-varid'>r</span> <span class='hs-keyglyph'>=</span> <a name="line-43"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>rs</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>readSTRef</span> <span class='hs-varid'>roots</span> <a name="line-44"></a> <span class='hs-varid'>writeSTRef</span> <span class='hs-varid'>roots</span> <span class='hs-layout'>(</span><span class='hs-varid'>r</span><span class='hs-conop'>:</span><span class='hs-varid'>rs</span><span class='hs-layout'>)</span> <a name="line-45"></a> <a name="line-46"></a> <span class='hs-varid'>new</span> <span class='hs-keyglyph'>=</span> <a name="line-47"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>rval</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newSTRef</span> <span class='hs-layout'>(</span><span class='hs-varid'>error</span> <span class='hs-str'>"val?"</span><span class='hs-layout'>)</span> <a name="line-48"></a> <span class='hs-varid'>rwir</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newSTRef</span> <span class='hs-layout'>(</span><span class='hs-varid'>error</span> <span class='hs-str'>"wire?"</span><span class='hs-layout'>)</span> <a name="line-49"></a> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-varid'>rval</span><span class='hs-layout'>,</span> <span class='hs-varid'>rwir</span><span class='hs-layout'>)</span> <a name="line-50"></a> <a name="line-51"></a> <span class='hs-varid'>define</span> <span class='hs-varid'>r</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=</span> <a name="line-52"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>s</span> <span class='hs-keyword'>of</span> <a name="line-53"></a> <span class='hs-conid'>DelayBool</span> <span class='hs-varid'>s</span> <span class='hs-varid'>s'</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>delay</span> <span class='hs-varid'>s</span> <span class='hs-varid'>s'</span> <a name="line-54"></a> <span class='hs-conid'>DelayInt</span> <span class='hs-varid'>s</span> <span class='hs-varid'>s'</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>delay</span> <span class='hs-varid'>s</span> <span class='hs-varid'>s'</span> <a name="line-55"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <a name="line-56"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>relate</span> <span class='hs-varid'>r</span> <span class='hs-layout'>(</span><span class='hs-varid'>arguments</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-varop'>$</span> <a name="line-57"></a> <span class='hs-varid'>eval</span> <span class='hs-varop'>`fmap`</span> <span class='hs-varid'>mmap</span> <span class='hs-layout'>(</span><span class='hs-varid'>readSTRef</span> <span class='hs-varop'>.</span> <span class='hs-varid'>fst</span><span class='hs-layout'>)</span> <span class='hs-varid'>s</span> <a name="line-58"></a> <span class='hs-keyword'>where</span> <a name="line-59"></a> <span class='hs-varid'>delay</span> <span class='hs-varid'>ri</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-varid'>rinit</span><span class='hs-layout'>,</span><span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-varid'>r1</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-varid'>pre</span><span class='hs-layout'>,</span><span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <a name="line-60"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>state</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newSTRef</span> <span class='hs-conid'>Nothing</span> <a name="line-61"></a> <span class='hs-varid'>r2</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>new</span> <a name="line-62"></a> <span class='hs-varid'>root</span> <span class='hs-varid'>r2</span> <a name="line-63"></a> <a name="line-64"></a> <span class='hs-varid'>relate</span> <span class='hs-varid'>r</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>ri</span><span class='hs-keyglyph'>]</span> <span class='hs-varop'>$</span> <a name="line-65"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>ms</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>readSTRef</span> <span class='hs-varid'>state</span> <a name="line-66"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>ms</span> <span class='hs-keyword'>of</span> <a name="line-67"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-varid'>s</span> <a name="line-68"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <a name="line-69"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>readSTRef</span> <span class='hs-varid'>rinit</span> <a name="line-70"></a> <span class='hs-varid'>writeSTRef</span> <span class='hs-varid'>state</span> <span class='hs-layout'>(</span><span class='hs-conid'>Just</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <a name="line-71"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>s</span> <a name="line-72"></a> <a name="line-73"></a> <span class='hs-varid'>relate</span> <span class='hs-varid'>r2</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>r</span><span class='hs-layout'>,</span><span class='hs-varid'>r1</span><span class='hs-keyglyph'>]</span> <span class='hs-varop'>$</span> <a name="line-74"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>readSTRef</span> <span class='hs-varid'>pre</span> <a name="line-75"></a> <span class='hs-varid'>writeSTRef</span> <span class='hs-varid'>state</span> <span class='hs-layout'>(</span><span class='hs-conid'>Just</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <a name="line-76"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>s</span> <a name="line-77"></a> <a name="line-78"></a> <span class='hs-varid'>sr</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>netlistST</span> <span class='hs-varid'>new</span> <span class='hs-varid'>define</span> <span class='hs-layout'>(</span><span class='hs-varid'>struct</span> <span class='hs-layout'>(</span><span class='hs-varid'>circ</span> <span class='hs-layout'>(</span><span class='hs-varid'>input</span> <span class='hs-varid'>inps</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <a name="line-79"></a> <span class='hs-varid'>rs</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>readSTRef</span> <span class='hs-varid'>roots</span> <a name="line-80"></a> <span class='hs-varid'>step</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>drive</span> <span class='hs-layout'>(</span><span class='hs-varid'>flatten</span> <span class='hs-varid'>sr</span> <span class='hs-varop'>++</span> <span class='hs-varid'>rs</span><span class='hs-layout'>)</span> <a name="line-81"></a> <a name="line-82"></a> <span class='hs-varid'>outs</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>lazyloop</span> <span class='hs-varop'>$</span> <a name="line-83"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>step</span> <a name="line-84"></a> <span class='hs-varid'>s</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>mmap</span> <span class='hs-layout'>(</span><span class='hs-varid'>fmap</span> <span class='hs-varid'>symbol</span> <span class='hs-varop'>.</span> <span class='hs-varid'>readSTRef</span> <span class='hs-varop'>.</span> <span class='hs-varid'>fst</span><span class='hs-layout'>)</span> <span class='hs-varid'>sr</span> <a name="line-85"></a> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-varid'>construct</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <a name="line-86"></a> <a name="line-87"></a> <span class='hs-keyword'>let</span> <span class='hs-varid'>res</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>takes</span> <span class='hs-varid'>inps</span> <span class='hs-varid'>outs</span> <a name="line-88"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>res</span> <a name="line-89"></a> <span class='hs-layout'>)</span> <a name="line-90"></a> <a name="line-91"></a><span class='hs-comment'>-- evaluation order</span> <a name="line-92"></a> <a name="line-93"></a><a name="relate"></a><span class='hs-definition'>relate</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Var</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Var</span> <span class='hs-varid'>s</span><span class='hs-keyglyph'>]</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'>S</span> <span class='hs-conid'>Symbol</span><span class='hs-layout'>)</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-94"></a><span class='hs-definition'>relate</span> <span class='hs-layout'>(</span><span class='hs-varid'>rval</span><span class='hs-layout'>,</span> <span class='hs-varid'>rwir</span><span class='hs-layout'>)</span> <span class='hs-varid'>rs</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <a name="line-95"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>writeSTRef</span> <span class='hs-varid'>rwir</span> <span class='hs-varop'>$</span> <a name="line-96"></a> <span class='hs-conid'>Wire</span><span class='hs-layout'>{</span> <span class='hs-varid'>dependencies</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>rs</span> <a name="line-97"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>kick</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>f</span> <a name="line-98"></a> <span class='hs-varid'>writeSTRef</span> <span class='hs-varid'>rval</span> <span class='hs-varid'>b</span> <a name="line-99"></a> <span class='hs-layout'>}</span> <a name="line-100"></a> <a name="line-101"></a><a name="drive"></a><span class='hs-definition'>drive</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Var</span> <span class='hs-varid'>s</span><span class='hs-keyglyph'>]</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'>ST</span> <span class='hs-varid'>s</span> <span class='hs-conid'>()</span><span class='hs-layout'>)</span> <a name="line-102"></a><span class='hs-definition'>drive</span> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>=</span> <a name="line-103"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-varid'>return</span> <span class='hs-conid'>()</span><span class='hs-layout'>)</span> <a name="line-104"></a> <a name="line-105"></a><span class='hs-definition'>drive</span> <span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-varid'>rval</span><span class='hs-layout'>,</span><span class='hs-varid'>rwir</span><span class='hs-layout'>)</span><span class='hs-conop'>:</span><span class='hs-varid'>rs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <a name="line-106"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>wire</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>readSTRef</span> <span class='hs-varid'>rwir</span> <a name="line-107"></a> <span class='hs-varid'>writeSTRef</span> <span class='hs-varid'>rwir</span> <span class='hs-layout'>(</span><span class='hs-varid'>error</span> <span class='hs-str'>"detected combinational loop"</span><span class='hs-layout'>)</span> <a name="line-108"></a> <span class='hs-varid'>driv1</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>drive</span> <span class='hs-layout'>(</span><span class='hs-varid'>dependencies</span> <span class='hs-varid'>wire</span><span class='hs-layout'>)</span> <a name="line-109"></a> <span class='hs-varid'>writeSTRef</span> <span class='hs-varid'>rwir</span> <span class='hs-varop'>$</span> <a name="line-110"></a> <span class='hs-conid'>Wire</span> <span class='hs-layout'>{</span> <span class='hs-varid'>dependencies</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>[]</span><span class='hs-layout'>,</span> <span class='hs-varid'>kick</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>return</span> <span class='hs-conid'>()</span> <span class='hs-layout'>}</span> <a name="line-111"></a> <span class='hs-varid'>driv2</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>drive</span> <span class='hs-varid'>rs</span> <a name="line-112"></a> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span> <a name="line-113"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>driv1</span> <a name="line-114"></a> <span class='hs-varid'>kick</span> <span class='hs-varid'>wire</span> <a name="line-115"></a> <span class='hs-varid'>driv2</span> <a name="line-116"></a> <a name="line-117"></a><span class='hs-comment'>----------------------------------------------------------------</span> <a name="line-118"></a><span class='hs-comment'>-- helper functions</span> <a name="line-119"></a> <a name="line-120"></a><a name="lazyloop"></a><span class='hs-definition'>lazyloop</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ST</span> <span class='hs-varid'>s</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-keyglyph'>[</span><span class='hs-varid'>a</span><span class='hs-keyglyph'>]</span> <a name="line-121"></a><span class='hs-definition'>lazyloop</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=</span> <a name="line-122"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>m</span> <a name="line-123"></a> <span class='hs-keyword'>as</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>unsafeInterleaveST</span> <span class='hs-layout'>(</span><span class='hs-varid'>lazyloop</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <a name="line-124"></a> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-conop'>:</span><span class='hs-keyword'>as</span><span class='hs-layout'>)</span> <a name="line-125"></a> <a name="line-126"></a><a name="input"></a><span class='hs-definition'>input</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Generic</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>a</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span> <a name="line-127"></a><span class='hs-definition'>input</span> <span class='hs-varid'>xs</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>out</span> <a name="line-128"></a> <span class='hs-keyword'>where</span> <a name="line-129"></a> <span class='hs-varid'>out</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>foldr</span> <span class='hs-varid'>delay</span> <span class='hs-varid'>out</span> <span class='hs-varid'>xs</span> <a name="line-130"></a> <a name="line-131"></a><a name="takes"></a><span class='hs-definition'>takes</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>a</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>b</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>b</span><span class='hs-keyglyph'>]</span> <a name="line-132"></a><span class='hs-definition'>takes</span> <span class='hs-conid'>[]</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>[]</span> <a name="line-133"></a><span class='hs-definition'>takes</span> <span class='hs-layout'>(</span><span class='hs-keyword'>_</span><span class='hs-conop'>:</span><span class='hs-varid'>xs</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>y</span><span class='hs-conop'>:</span><span class='hs-varid'>ys</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>y</span> <span class='hs-conop'>:</span> <span class='hs-varid'>takes</span> <span class='hs-varid'>xs</span> <span class='hs-varid'>ys</span> <a name="line-134"></a> <a name="line-135"></a><span class='hs-comment'>----------------------------------------------------------------</span> <a name="line-136"></a><span class='hs-comment'>-- the end.</span> <a name="line-137"></a> </pre></body> </html>