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<title>src/Hint/Lambda.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE ViewPatterns, PatternGuards #-}</span>
<a name="line-2"></a>
<a name="line-3"></a><span class='hs-comment'>{-
<a name="line-4"></a> Concept:
<a name="line-5"></a> Remove all the lambdas you can be inserting only sections
<a name="line-6"></a> Never create a right section with +-# as the operator (they are misparsed)
<a name="line-7"></a>
<a name="line-8"></a> Rules:
<a name="line-9"></a> fun a = \x -> y -- promote lambdas, provided no where's outside the lambda
<a name="line-10"></a> fun x = y x -- eta reduce, x /= mr and foo /= symbol
<a name="line-11"></a> \x -> y x -- eta reduce
<a name="line-12"></a> ((#) x) ==> (x #) -- rotate operators
<a name="line-13"></a> (flip op x) ==> (`op` x) -- rotate operators
<a name="line-14"></a> \x y -> x + y ==> (+) -- insert operator
<a name="line-15"></a> \x y -> op y x ==> flip op
<a name="line-16"></a> \x -> x + y ==> (+ y) -- insert section,
<a name="line-17"></a> \x -> op x y ==> (`op` y) -- insert section
<a name="line-18"></a> \x -> y + x ==> (y +) -- insert section
<a name="line-19"></a> \x -> \y -> ... ==> \x y -- lambda compression
<a name="line-20"></a>
<a name="line-21"></a><TEST>
<a name="line-22"></a>f a = \x -> x + x -- f a x = x + x
<a name="line-23"></a>f a = \x -> x + x where _ = test
<a name="line-24"></a>fun x y z = f x y z -- fun = f
<a name="line-25"></a>fun x y z = f x x y z -- fun x = f x x
<a name="line-26"></a>fun x y z = f g z -- fun x y = f g
<a name="line-27"></a>fun mr = y mr
<a name="line-28"></a>f = foo ((*) x) -- (x *)
<a name="line-29"></a>f = (*) x
<a name="line-30"></a>f = foo (flip op x) -- (`op` x)
<a name="line-31"></a>f = flip op x
<a name="line-32"></a>f = foo (flip (*) x) -- (* x)
<a name="line-33"></a>f = foo (flip (-) x)
<a name="line-34"></a>f = foo (\x y -> fun x y) -- fun
<a name="line-35"></a>f = foo (\x y -> x + y) -- (+)
<a name="line-36"></a>f = foo (\x -> x * y) -- (* y)
<a name="line-37"></a>f = foo (\x -> x # y)
<a name="line-38"></a>f = foo (\x -> \y -> x x y y) -- \x y -> x x y y
<a name="line-39"></a>f = foo (\x -> \x -> foo x x)
<a name="line-40"></a>x ! y = fromJust $ lookup x y
<a name="line-41"></a>f = foo (\i -> writeIdea (getClass i) i)
<a name="line-42"></a>f = bar (flip Foo.bar x) -- (`Foo.bar` x)
<a name="line-43"></a>f = a b (\x -> c x d) -- (`c` d)
<a name="line-44"></a>yes = \x -> a x -- a
<a name="line-45"></a>yes = \x y -> op y x -- flip op
<a name="line-46"></a>f = \y -> nub $ reverse y -- nub . reverse
<a name="line-47"></a>f = \z -> foo $ bar $ baz z -- foo . bar . baz
<a name="line-48"></a>f = \z -> foo $ bar x $ baz z -- foo . bar x . baz
<a name="line-49"></a>f = \z -> foo $ z $ baz z
<a name="line-50"></a>f = \x -> bar map (filter x) -- bar map . filter
<a name="line-51"></a>f = bar &+& \x -> f (g x)
<a name="line-52"></a>foo = [\column -> set column [treeViewColumnTitle := printf "%s (match %d)" name (length candidnates)]]
<a name="line-53"></a>foo = [\x -> x]
<a name="line-54"></a></TEST>
<a name="line-55"></a>-}</span>
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<a name="line-58"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Hint</span><span class='hs-varop'>.</span><span class='hs-conid'>Lambda</span> <span class='hs-keyword'>where</span>
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<a name="line-60"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Hint</span><span class='hs-varop'>.</span><span class='hs-conid'>Util</span>
<a name="line-61"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Hint</span><span class='hs-varop'>.</span><span class='hs-conid'>Type</span>
<a name="line-62"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Util</span>
<a name="line-63"></a>
<a name="line-64"></a>
<a name="line-65"></a><a name="lambdaHint"></a><span class='hs-definition'>lambdaHint</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>DeclHint</span>
<a name="line-66"></a><span class='hs-definition'>lambdaHint</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>concatMap</span> <span class='hs-layout'>(</span><span class='hs-varid'>uncurry</span> <span class='hs-varid'>lambdaExp</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>universeParentBi</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-varop'>++</span> <span class='hs-varid'>concatMap</span> <span class='hs-varid'>lambdaDecl</span> <span class='hs-layout'>(</span><span class='hs-varid'>universe</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span>
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<a name="line-68"></a>
<a name="line-69"></a><a name="lambdaDecl"></a><span class='hs-definition'>lambdaDecl</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Decl_</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Idea</span><span class='hs-keyglyph'>]</span>
<a name="line-70"></a><span class='hs-definition'>lambdaDecl</span> <span class='hs-varid'>o</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>FunBind</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Match</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>name</span> <span class='hs-varid'>pats</span> <span class='hs-layout'>(</span><span class='hs-conid'>UnGuardedRhs</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>bod</span><span class='hs-layout'>)</span> <span class='hs-conid'>Nothing</span><span class='hs-keyglyph'>]</span><span class='hs-layout'>)</span>
<a name="line-71"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>Lambda</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>vs</span> <span class='hs-varid'>y</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>bod</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>err</span> <span class='hs-str'>"Redundant lambda"</span> <span class='hs-varid'>o</span> <span class='hs-varop'>$</span> <span class='hs-varid'>reform</span> <span class='hs-layout'>(</span><span class='hs-varid'>pats</span><span class='hs-varop'>++</span><span class='hs-varid'>vs</span><span class='hs-layout'>)</span> <span class='hs-varid'>y</span><span class='hs-keyglyph'>]</span>
<a name="line-72"></a> <span class='hs-keyglyph'>|</span> <span class='hs-layout'>(</span><span class='hs-varid'>pats2</span><span class='hs-layout'>,</span><span class='hs-varid'>bod2</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>etaReduce</span> <span class='hs-varid'>pats</span> <span class='hs-varid'>bod</span><span class='hs-layout'>,</span> <span class='hs-varid'>length</span> <span class='hs-varid'>pats2</span> <span class='hs-varop'><</span> <span class='hs-varid'>length</span> <span class='hs-varid'>pats</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>err</span> <span class='hs-str'>"Eta reduce"</span> <span class='hs-varid'>o</span> <span class='hs-varop'>$</span> <span class='hs-varid'>reform</span> <span class='hs-varid'>pats2</span> <span class='hs-varid'>bod2</span><span class='hs-keyglyph'>]</span>
<a name="line-73"></a> <span class='hs-keyword'>where</span> <span class='hs-varid'>reform</span> <span class='hs-varid'>p</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>FunBind</span> <span class='hs-varid'>an</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Match</span> <span class='hs-varid'>an</span> <span class='hs-varid'>name</span> <span class='hs-varid'>p</span> <span class='hs-layout'>(</span><span class='hs-conid'>UnGuardedRhs</span> <span class='hs-varid'>an</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-conid'>Nothing</span><span class='hs-keyglyph'>]</span>
<a name="line-74"></a><span class='hs-definition'>lambdaDecl</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>[]</span>
<a name="line-75"></a>
<a name="line-76"></a>
<a name="line-77"></a><a name="etaReduce"></a><span class='hs-definition'>etaReduce</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Pat_</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-layout'>(</span><span class='hs-keyglyph'>[</span><span class='hs-conid'>Pat_</span><span class='hs-keyglyph'>]</span><span class='hs-layout'>,</span> <span class='hs-conid'>Exp_</span><span class='hs-layout'>)</span>
<a name="line-78"></a><span class='hs-definition'>etaReduce</span> <span class='hs-varid'>ps</span> <span class='hs-layout'>(</span><span class='hs-conid'>App</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>x</span> <span class='hs-layout'>(</span><span class='hs-conid'>Var</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>UnQual</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>Ident</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-79"></a> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>ps</span> <span class='hs-varop'>/=</span> <span class='hs-conid'>[]</span><span class='hs-layout'>,</span> <span class='hs-conid'>PVar</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>Ident</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>p</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>last</span> <span class='hs-varid'>ps</span><span class='hs-layout'>,</span> <span class='hs-varid'>p</span> <span class='hs-varop'>==</span> <span class='hs-varid'>y</span><span class='hs-layout'>,</span> <span class='hs-varid'>p</span> <span class='hs-varop'>/=</span> <span class='hs-str'>"mr"</span><span class='hs-layout'>,</span> <span class='hs-varid'>y</span> <span class='hs-varop'>`notElem`</span> <span class='hs-varid'>vars</span> <span class='hs-varid'>x</span>
<a name="line-80"></a> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>etaReduce</span> <span class='hs-layout'>(</span><span class='hs-varid'>init</span> <span class='hs-varid'>ps</span><span class='hs-layout'>)</span> <span class='hs-varid'>x</span>
<a name="line-81"></a><span class='hs-definition'>etaReduce</span> <span class='hs-varid'>ps</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-varid'>ps</span><span class='hs-layout'>,</span><span class='hs-varid'>x</span><span class='hs-layout'>)</span>
<a name="line-82"></a>
<a name="line-83"></a>
<a name="line-84"></a><a name="lambdaExp"></a><span class='hs-definition'>lambdaExp</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Maybe</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-keyglyph'>[</span><span class='hs-conid'>Idea</span><span class='hs-keyglyph'>]</span>
<a name="line-85"></a><span class='hs-definition'>lambdaExp</span> <span class='hs-varid'>p</span> <span class='hs-varid'>o</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>Paren</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>App</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>Var</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>UnQual</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>Symbol</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>isAtom</span> <span class='hs-varid'>y</span><span class='hs-layout'>,</span> <span class='hs-varid'>allowLeftSection</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span>
<a name="line-86"></a> <span class='hs-keyglyph'>[</span><span class='hs-varid'>warn</span> <span class='hs-str'>"Use section"</span> <span class='hs-varid'>o</span> <span class='hs-varop'>$</span> <span class='hs-conid'>LeftSection</span> <span class='hs-varid'>an</span> <span class='hs-varid'>y</span> <span class='hs-layout'>(</span><span class='hs-varid'>toNamed</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span><span class='hs-keyglyph'>]</span>
<a name="line-87"></a><span class='hs-definition'>lambdaExp</span> <span class='hs-varid'>p</span> <span class='hs-varid'>o</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>Paren</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>App</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>App</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-varid'>view</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Var_</span> <span class='hs-str'>"flip"</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Var</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>allowRightSection</span> <span class='hs-varop'>$</span> <span class='hs-varid'>fromNamed</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span>
<a name="line-88"></a> <span class='hs-keyglyph'>[</span><span class='hs-varid'>warn</span> <span class='hs-str'>"Use section"</span> <span class='hs-varid'>o</span> <span class='hs-varop'>$</span> <span class='hs-conid'>RightSection</span> <span class='hs-varid'>an</span> <span class='hs-layout'>(</span><span class='hs-conid'>QVarOp</span> <span class='hs-varid'>an</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-varid'>y</span><span class='hs-keyglyph'>]</span>
<a name="line-89"></a><span class='hs-definition'>lambdaExp</span> <span class='hs-varid'>p</span> <span class='hs-varid'>o</span><span class='hs-keyglyph'>@</span><span class='hs-conid'>Lambda</span><span class='hs-layout'>{</span><span class='hs-layout'>}</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>maybe</span> <span class='hs-conid'>True</span> <span class='hs-layout'>(</span><span class='hs-varid'>not</span> <span class='hs-varop'>.</span> <span class='hs-varid'>isInfixApp</span><span class='hs-layout'>)</span> <span class='hs-varid'>p</span><span class='hs-layout'>,</span> <span class='hs-varid'>res</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>niceLambda</span> <span class='hs-conid'>[]</span> <span class='hs-varid'>o</span><span class='hs-layout'>,</span> <span class='hs-varid'>not</span> <span class='hs-varop'>$</span> <span class='hs-varid'>isLambda</span> <span class='hs-varid'>res</span> <span class='hs-keyglyph'>=</span>
<a name="line-90"></a> <span class='hs-keyglyph'>[</span><span class='hs-varid'>warn</span> <span class='hs-str'>"Avoid lambda"</span> <span class='hs-varid'>o</span> <span class='hs-varid'>res</span><span class='hs-keyglyph'>]</span>
<a name="line-91"></a><span class='hs-definition'>lambdaExp</span> <span class='hs-varid'>p</span> <span class='hs-varid'>o</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>Lambda</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>ps1</span> <span class='hs-layout'>(</span><span class='hs-varid'>fromParen</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Lambda</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>ps2</span> <span class='hs-varid'>bod</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>pvars</span> <span class='hs-varid'>ps1</span> <span class='hs-varop'>`disjoint`</span> <span class='hs-varid'>pvars</span> <span class='hs-varid'>ps2</span> <span class='hs-keyglyph'>=</span>
<a name="line-92"></a> <span class='hs-keyglyph'>[</span><span class='hs-varid'>warn</span> <span class='hs-str'>"Collapse lambdas"</span> <span class='hs-varid'>o</span> <span class='hs-varop'>$</span> <span class='hs-conid'>Lambda</span> <span class='hs-varid'>an</span> <span class='hs-layout'>(</span><span class='hs-varid'>ps1</span><span class='hs-varop'>++</span><span class='hs-varid'>ps2</span><span class='hs-layout'>)</span> <span class='hs-varid'>bod</span><span class='hs-keyglyph'>]</span>
<a name="line-93"></a><span class='hs-definition'>lambdaExp</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>[]</span>
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