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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE PatternGuards, ViewPatterns #-}</span>
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<a name="line-3"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Hint</span><span class='hs-varop'>.</span><span class='hs-conid'>Util</span> <span class='hs-keyword'>where</span>
<a name="line-4"></a>
<a name="line-5"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>HSE</span><span class='hs-varop'>.</span><span class='hs-conid'>All</span>
<a name="line-6"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Util</span>
<a name="line-7"></a>
<a name="line-8"></a>
<a name="line-9"></a><a name="niceLambda"></a><span class='hs-comment'>-- | Generate a lambda, but prettier (if possible).</span>
<a name="line-10"></a><span class='hs-comment'>-- Generally no lambda is good, but removing just some arguments isn't so useful.</span>
<a name="line-11"></a><span class='hs-definition'>niceLambda</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>String</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Exp_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Exp_</span>
<a name="line-12"></a>
<a name="line-13"></a><span class='hs-comment'>-- \xs -> (e) ==> \xs -> e</span>
<a name="line-14"></a><span class='hs-definition'>niceLambda</span> <span class='hs-varid'>xs</span> <span class='hs-layout'>(</span><span class='hs-conid'>Paren</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>niceLambda</span> <span class='hs-varid'>xs</span> <span class='hs-varid'>x</span>
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<a name="line-16"></a><span class='hs-comment'>-- \xs -> \v vs -> e ==> \xs v -> \vs -> e</span>
<a name="line-17"></a><span class='hs-comment'>-- \xs -> \ -> e ==> \xs -> e</span>
<a name="line-18"></a><span class='hs-definition'>niceLambda</span> <span class='hs-varid'>xs</span> <span class='hs-layout'>(</span><span class='hs-conid'>Lambda</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-varid'>view</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PVar_</span> <span class='hs-varid'>v</span><span class='hs-layout'>)</span><span class='hs-conop'>:</span><span class='hs-varid'>vs</span><span class='hs-layout'>)</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>v</span> <span class='hs-varop'>`notElem`</span> <span class='hs-varid'>xs</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>niceLambda</span> <span class='hs-layout'>(</span><span class='hs-varid'>xs</span><span class='hs-varop'>++</span><span class='hs-keyglyph'>[</span><span class='hs-varid'>v</span><span class='hs-keyglyph'>]</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Lambda</span> <span class='hs-varid'>an</span> <span class='hs-varid'>vs</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span>
<a name="line-19"></a><span class='hs-definition'>niceLambda</span> <span class='hs-varid'>xs</span> <span class='hs-layout'>(</span><span class='hs-conid'>Lambda</span> <span class='hs-keyword'>_</span> <span class='hs-conid'>[]</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>niceLambda</span> <span class='hs-varid'>xs</span> <span class='hs-varid'>x</span>
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<a name="line-21"></a><span class='hs-comment'>-- \ -> e ==> e</span>
<a name="line-22"></a><span class='hs-definition'>niceLambda</span> <span class='hs-conid'>[]</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>x</span>
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<a name="line-24"></a><span class='hs-comment'>-- \xs -> e xs ==> e</span>
<a name="line-25"></a><span class='hs-definition'>niceLambda</span> <span class='hs-varid'>xs</span> <span class='hs-layout'>(</span><span class='hs-varid'>fromApps</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>map</span> <span class='hs-varid'>view</span> <span class='hs-varid'>xs2</span> <span class='hs-varop'>==</span> <span class='hs-varid'>map</span> <span class='hs-conid'>Var_</span> <span class='hs-varid'>xs</span><span class='hs-layout'>,</span> <span class='hs-varid'>vars</span> <span class='hs-varid'>e2</span> <span class='hs-varop'>`disjoint`</span> <span class='hs-varid'>xs</span><span class='hs-layout'>,</span> <span class='hs-varid'>notNull</span> <span class='hs-varid'>e2</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>apps</span> <span class='hs-varid'>e2</span>
<a name="line-26"></a> <span class='hs-keyword'>where</span> <span class='hs-layout'>(</span><span class='hs-varid'>e2</span><span class='hs-layout'>,</span><span class='hs-varid'>xs2</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>splitAt</span> <span class='hs-layout'>(</span><span class='hs-varid'>length</span> <span class='hs-varid'>e</span> <span class='hs-comment'>-</span> <span class='hs-varid'>length</span> <span class='hs-varid'>xs</span><span class='hs-layout'>)</span> <span class='hs-varid'>e</span>
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<a name="line-28"></a><span class='hs-comment'>-- \x y -> x + y ==> (+)</span>
<a name="line-29"></a><span class='hs-definition'>niceLambda</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>x</span><span class='hs-layout'>,</span><span class='hs-varid'>y</span><span class='hs-keyglyph'>]</span> <span class='hs-layout'>(</span><span class='hs-conid'>InfixApp</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-varid'>view</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Var_</span> <span class='hs-varid'>x1</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>opExp</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>op</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>view</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Var_</span> <span class='hs-varid'>y1</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-30"></a> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>x</span> <span class='hs-varop'>==</span> <span class='hs-varid'>x1</span><span class='hs-layout'>,</span> <span class='hs-varid'>y</span> <span class='hs-varop'>==</span> <span class='hs-varid'>y1</span><span class='hs-layout'>,</span> <span class='hs-varid'>vars</span> <span class='hs-varid'>op</span> <span class='hs-varop'>`disjoint`</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>x</span><span class='hs-layout'>,</span><span class='hs-varid'>y</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>op</span>
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<a name="line-32"></a><span class='hs-comment'>-- \x -> x + b ==> (+ b) [heuristic, b must be a single lexeme, or gets too complex]</span>
<a name="line-33"></a><span class='hs-definition'>niceLambda</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>x</span><span class='hs-keyglyph'>]</span> <span class='hs-layout'>(</span><span class='hs-varid'>view</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>App2</span> <span class='hs-layout'>(</span><span class='hs-varid'>expOp</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Just</span> <span class='hs-varid'>op</span><span class='hs-layout'>)</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span>
<a name="line-34"></a> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>isLexeme</span> <span class='hs-varid'>b</span><span class='hs-layout'>,</span> <span class='hs-varid'>view</span> <span class='hs-varid'>a</span> <span class='hs-varop'>==</span> <span class='hs-conid'>Var_</span> <span class='hs-varid'>x</span><span class='hs-layout'>,</span> <span class='hs-varid'>x</span> <span class='hs-varop'>`notElem`</span> <span class='hs-varid'>vars</span> <span class='hs-varid'>b</span><span class='hs-layout'>,</span> <span class='hs-varid'>allowRightSection</span> <span class='hs-layout'>(</span><span class='hs-varid'>fromNamed</span> <span class='hs-varid'>op</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>rebracket1</span> <span class='hs-varop'>$</span> <span class='hs-conid'>RightSection</span> <span class='hs-varid'>an</span> <span class='hs-varid'>op</span> <span class='hs-varid'>b</span>
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<a name="line-36"></a><span class='hs-comment'>-- \x y -> f y x = flip f</span>
<a name="line-37"></a><span class='hs-definition'>niceLambda</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>x</span><span class='hs-layout'>,</span><span class='hs-varid'>y</span><span class='hs-keyglyph'>]</span> <span class='hs-layout'>(</span><span class='hs-varid'>view</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>App2</span> <span class='hs-varid'>op</span> <span class='hs-layout'>(</span><span class='hs-varid'>view</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Var_</span> <span class='hs-varid'>y1</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>view</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Var_</span> <span class='hs-varid'>x1</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-38"></a> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>x</span> <span class='hs-varop'>==</span> <span class='hs-varid'>x1</span> <span class='hs-varop'>&&</span> <span class='hs-varid'>y</span> <span class='hs-varop'>==</span> <span class='hs-varid'>y1</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>App</span> <span class='hs-varid'>an</span> <span class='hs-layout'>(</span><span class='hs-varid'>toNamed</span> <span class='hs-str'>"flip"</span><span class='hs-layout'>)</span> <span class='hs-varid'>op</span>
<a name="line-39"></a>
<a name="line-40"></a><span class='hs-comment'>-- \x -> f (b x) ==> f . b</span>
<a name="line-41"></a><span class='hs-comment'>-- \x -> f $ b x ==> f . b</span>
<a name="line-42"></a><span class='hs-definition'>niceLambda</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>x</span><span class='hs-keyglyph'>]</span> <span class='hs-varid'>y</span> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>z</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>factor</span> <span class='hs-varid'>y</span><span class='hs-layout'>,</span> <span class='hs-varid'>x</span> <span class='hs-varop'>`notElem`</span> <span class='hs-varid'>vars</span> <span class='hs-varid'>z</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>z</span>
<a name="line-43"></a> <span class='hs-keyword'>where</span>
<a name="line-44"></a> <span class='hs-comment'>-- factor the expression with respect to x</span>
<a name="line-45"></a> <span class='hs-varid'>factor</span> <span class='hs-varid'>y</span><span class='hs-keyglyph'>@</span><span class='hs-conid'>App</span><span class='hs-layout'>{</span><span class='hs-layout'>}</span> <span class='hs-keyglyph'>|</span> <span class='hs-layout'>(</span><span class='hs-varid'>ini</span><span class='hs-layout'>,</span><span class='hs-varid'>lst</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>unsnoc</span> <span class='hs-varop'>$</span> <span class='hs-varid'>fromApps</span> <span class='hs-varid'>y</span><span class='hs-layout'>,</span> <span class='hs-varid'>view</span> <span class='hs-varid'>lst</span> <span class='hs-varop'>==</span> <span class='hs-conid'>Var_</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varop'>$</span> <span class='hs-varid'>apps</span> <span class='hs-varid'>ini</span>
<a name="line-46"></a> <span class='hs-varid'>factor</span> <span class='hs-varid'>y</span><span class='hs-keyglyph'>@</span><span class='hs-conid'>App</span><span class='hs-layout'>{</span><span class='hs-layout'>}</span> <span class='hs-keyglyph'>|</span> <span class='hs-layout'>(</span><span class='hs-varid'>ini</span><span class='hs-layout'>,</span><span class='hs-varid'>lst</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>unsnoc</span> <span class='hs-varop'>$</span> <span class='hs-varid'>fromApps</span> <span class='hs-varid'>y</span><span class='hs-layout'>,</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>z</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>factor</span> <span class='hs-varid'>lst</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varop'>$</span> <span class='hs-varid'>niceDotApp</span> <span class='hs-layout'>(</span><span class='hs-varid'>apps</span> <span class='hs-varid'>ini</span><span class='hs-layout'>)</span> <span class='hs-varid'>z</span>
<a name="line-47"></a> <span class='hs-varid'>factor</span> <span class='hs-layout'>(</span><span class='hs-conid'>InfixApp</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>y</span> <span class='hs-varid'>op</span> <span class='hs-layout'>(</span><span class='hs-varid'>factor</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Just</span> <span class='hs-varid'>z</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>isDol</span> <span class='hs-varid'>op</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varop'>$</span> <span class='hs-varid'>niceDotApp</span> <span class='hs-varid'>y</span> <span class='hs-varid'>z</span>
<a name="line-48"></a> <span class='hs-varid'>factor</span> <span class='hs-layout'>(</span><span class='hs-conid'>Paren</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>y</span><span class='hs-keyglyph'>@</span><span class='hs-conid'>App</span><span class='hs-layout'>{</span><span class='hs-layout'>}</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>factor</span> <span class='hs-varid'>y</span>
<a name="line-49"></a> <span class='hs-varid'>factor</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-50"></a>
<a name="line-51"></a><span class='hs-comment'>-- base case</span>
<a name="line-52"></a><span class='hs-definition'>niceLambda</span> <span class='hs-varid'>ps</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Lambda</span> <span class='hs-varid'>an</span> <span class='hs-layout'>(</span><span class='hs-varid'>map</span> <span class='hs-varid'>toNamed</span> <span class='hs-varid'>ps</span><span class='hs-layout'>)</span> <span class='hs-varid'>x</span>
<a name="line-53"></a>
<a name="line-54"></a>
<a name="line-55"></a>
<a name="line-56"></a><a name="niceDotApp"></a><span class='hs-comment'>-- ($) . b ==> b</span>
<a name="line-57"></a><span class='hs-definition'>niceDotApp</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exp_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Exp_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Exp_</span>
<a name="line-58"></a><span class='hs-definition'>niceDotApp</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>a</span> <span class='hs-varop'>~=</span> <span class='hs-str'>"$"</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>b</span>
<a name="line-59"></a> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>otherwise</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>dotApp</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span>
<a name="line-60"></a>
<a name="line-61"></a>
<a name="line-62"></a>
<a name="line-63"></a><a name="simplifyExp"></a><span class='hs-comment'>-- | Convert expressions which have redundant junk in them away.</span>
<a name="line-64"></a><span class='hs-comment'>-- Mainly so that later stages can match on fewer alternatives.</span>
<a name="line-65"></a><span class='hs-definition'>simplifyExp</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exp_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Exp_</span>
<a name="line-66"></a><span class='hs-definition'>simplifyExp</span> <span class='hs-layout'>(</span><span class='hs-conid'>InfixApp</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>x</span> <span class='hs-varid'>dol</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>isDol</span> <span class='hs-varid'>dol</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>App</span> <span class='hs-varid'>an</span> <span class='hs-varid'>x</span> <span class='hs-layout'>(</span><span class='hs-varid'>paren</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span>
<a name="line-67"></a><span class='hs-definition'>simplifyExp</span> <span class='hs-layout'>(</span><span class='hs-conid'>Let</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>BDecls</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>PatBind</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-varid'>view</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PVar_</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-conid'>Nothing</span> <span class='hs-layout'>(</span><span class='hs-conid'>UnGuardedRhs</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-conid'>Nothing</span><span class='hs-keyglyph'>]</span><span class='hs-layout'>)</span> <span class='hs-varid'>z</span><span class='hs-layout'>)</span>
<a name="line-68"></a> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>x</span> <span class='hs-varop'>`notElem`</span> <span class='hs-varid'>vars</span> <span class='hs-varid'>y</span> <span class='hs-varop'>&&</span> <span class='hs-varid'>x</span> <span class='hs-varop'>`notElem`</span> <span class='hs-varid'>pvars</span> <span class='hs-varid'>z</span> <span class='hs-varop'>&&</span> <span class='hs-varid'>length</span> <span class='hs-layout'>(</span><span class='hs-varid'>filter</span> <span class='hs-layout'>(</span><span class='hs-varop'>==</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>vars</span> <span class='hs-varid'>z</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-varop'><=</span> <span class='hs-num'>1</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>transform</span> <span class='hs-varid'>f</span> <span class='hs-varid'>z</span>
<a name="line-69"></a> <span class='hs-keyword'>where</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-varid'>view</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Var_</span> <span class='hs-varid'>x'</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>x</span> <span class='hs-varop'>==</span> <span class='hs-varid'>x'</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>paren</span> <span class='hs-varid'>y</span>
<a name="line-70"></a> <span class='hs-varid'>f</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>x</span>
<a name="line-71"></a><span class='hs-definition'>simplifyExp</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>x</span>
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