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</script></head><body><div id="package-header"><ul class="links" id="page-menu"><li><a href="src/Data-Generics-UniplateStr.html">Source</a></li><li><a href="index.html">Contents</a></li><li><a href="doc-index.html">Index</a></li></ul><p class="caption">uniplate-1.6: Help writing simple, concise and fast generic operations.</p></div><div id="content"><div id="module-header"><p class="caption">Data.Generics.UniplateStr</p></div><div id="table-of-contents"><p class="caption">Contents</p><ul><li><a href="#g:1">The Class
</a></li><li><a href="#g:2">The Operations
</a><ul><li><a href="#g:3">Queries
</a></li><li><a href="#g:4">Transformations
</a></li><li><a href="#g:5">Others
</a></li></ul></li></ul></div><div id="description"><p class="caption">Description</p><div class="doc"><p><em>RECOMMENDATION</em>: Use <a href="Data-Generics-Uniplate-Operations.html">Data.Generics.Uniplate.Operations</a> instead.
</p><p>This is the main Uniplate module, which defines all the essential operations
in a Haskell 98 compatible manner.
</p><p>Most functions have an example of a possible use for the function.
To illustate, I have used the <code>Expr</code> type as below:
</p><pre> data Expr = Val Int
| Neg Expr
| Add Expr Expr
</pre></div></div><div id="synopsis"><p id="control.syn" class="caption expander" onclick="toggleSection('syn')">Synopsis</p><ul id="section.syn" class="hide" onclick="toggleSection('syn')"><li class="src short"><span class="keyword">type</span> <a href="#t:UniplateType">UniplateType</a> on = on -> (<a href="Data-Generics-Str.html#t:Str">Str</a> on, <a href="Data-Generics-Str.html#t:Str">Str</a> on -> on)</li><li class="src short"><span class="keyword">class</span> <a href="#t:Uniplate">Uniplate</a> on <span class="keyword">where</span><ul class="subs"><li><a href="#v:uniplate">uniplate</a> :: <a href="Data-Generics-UniplateStr.html#t:UniplateType">UniplateType</a> on</li></ul></li><li class="src short"><a href="#v:uniplateList">uniplateList</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => on -> ([on], [on] -> on)</li><li class="src short"><a href="#v:universe">universe</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => on -> [on]</li><li class="src short"><a href="#v:children">children</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => on -> [on]</li><li class="src short"><a href="#v:transform">transform</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => (on -> on) -> on -> on</li><li class="src short"><a href="#v:transformM">transformM</a> :: (<a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Control-Monad.html#t:Monad">Monad</a> m, <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on) => (on -> m on) -> on -> m on</li><li class="src short"><a href="#v:rewrite">rewrite</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => (on -> <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Maybe.html#t:Maybe">Maybe</a> on) -> on -> on</li><li class="src short"><a href="#v:rewriteM">rewriteM</a> :: (<a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Control-Monad.html#t:Monad">Monad</a> m, <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on) => (on -> m (<a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Maybe.html#t:Maybe">Maybe</a> on)) -> on -> m on</li><li class="src short"><a href="#v:descend">descend</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => (on -> on) -> on -> on</li><li class="src short"><a href="#v:descendM">descendM</a> :: (<a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Control-Monad.html#t:Monad">Monad</a> m, <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on) => (on -> m on) -> on -> m on</li><li class="src short"><a href="#v:contexts">contexts</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => on -> [(on, on -> on)]</li><li class="src short"><a href="#v:holes">holes</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => on -> [(on, on -> on)]</li><li class="src short"><a href="#v:para">para</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => (on -> [r] -> r) -> on -> r</li><li class="src short">module <a href="Data-Generics-Str.html">Data.Generics.Str</a></li></ul></div><div id="interface"><h1 id="g:1">The Class
</h1><div class="top"><p class="src"><span class="keyword">type</span> <a name="t:UniplateType" class="def">UniplateType</a> on = on -> (<a href="Data-Generics-Str.html#t:Str">Str</a> on, <a href="Data-Generics-Str.html#t:Str">Str</a> on -> on)<a href="src/Data-Generics-UniplateStr.html#UniplateType" class="link">Source</a></p><div class="doc"><p>The type of replacing all the children of a node
</p><p>Taking a value, the function should return all the immediate children
of the same type, and a function to replace them.
</p></div></div><div class="top"><p class="src"><span class="keyword">class</span> <a name="t:Uniplate" class="def">Uniplate</a> on <span class="keyword">where</span><a href="src/Data-Generics-UniplateStr.html#Uniplate" class="link">Source</a></p><div class="doc"><p>The standard Uniplate class, all operations require this.
</p></div><div class="subs methods"><p class="caption">Methods</p><p class="src"><a name="v:uniplate" class="def">uniplate</a> :: <a href="Data-Generics-UniplateStr.html#t:UniplateType">UniplateType</a> on<a href="src/Data-Generics-UniplateStr.html#uniplate" class="link">Source</a></p><div class="doc"><p>The underlying method in the class.
</p><p>Given <code>uniplate x = (cs, gen)</code>
</p><p><code>cs</code> should be a <code>Str on</code>, constructed of <code>Zero</code>, <code>One</code> and <code>Two</code>,
containing all <code>x</code>'s direct children of the same type as <code>x</code>. <code>gen</code>
should take a <code>Str on</code> with exactly the same structure as <code>cs</code>,
and generate a new element with the children replaced.
</p><p>Example instance:
</p><pre> instance Uniplate Expr where
uniplate (Val i ) = (Zero , \Zero -> Val i )
uniplate (Neg a ) = (One a , \(One a) -> Neg a )
uniplate (Add a b) = (Two (One a) (One b), \(Two (One a) (One b)) -> Add a b)
</pre></div></div><div class="subs instances"><p id="control.i:Uniplate" class="caption collapser" onclick="toggleSection('i:Uniplate')">Instances</p><div id="section.i:Uniplate" class="show"><table><tr><td class="src"><a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Bool.html#t:Bool">Bool</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Char.html#t:Char">Char</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Prelude.html#t:Double">Double</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Prelude.html#t:Float">Float</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Int.html#t:Int">Int</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Prelude.html#t:Integer">Integer</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> ()</td><td class="doc empty"> </td></tr><tr><td class="src">(<a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Data.html#t:Data">Data</a> a, <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Typeable.html#t:Typeable">Typeable</a> a) => <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> a</td><td class="doc empty"> </td></tr></table></div></div></div><div class="top"><p class="src"><a name="v:uniplateList" class="def">uniplateList</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => on -> ([on], [on] -> on)<a href="src/Data-Generics-UniplateStr.html#uniplateList" class="link">Source</a></p><div class="doc"><p>Compatibility method, for direct users of the old list-based <code><a href="Data-Generics-UniplateStr.html#v:uniplate">uniplate</a></code> function
</p></div></div><h1 id="g:2">The Operations
</h1><h2 id="g:3">Queries
</h2><div class="top"><p class="src"><a name="v:universe" class="def">universe</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => on -> [on]<a href="src/Data-Generics-UniplateStr.html#universe" class="link">Source</a></p><div class="doc"><p>Get all the children of a node, including itself and all children.
</p><pre> universe (Add (Val 1) (Neg (Val 2))) =
[Add (Val 1) (Neg (Val 2)), Val 1, Neg (Val 2), Val 2]
</pre><p>This method is often combined with a list comprehension, for example:
</p><pre> vals x = [i | Val i <- universe x]
</pre></div></div><div class="top"><p class="src"><a name="v:children" class="def">children</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => on -> [on]<a href="src/Data-Generics-UniplateStr.html#children" class="link">Source</a></p><div class="doc"><p>Get the direct children of a node. Usually using <code><a href="Data-Generics-UniplateStr.html#v:universe">universe</a></code> is more appropriate.
</p><pre>children = fst . <code><a href="Data-Generics-UniplateStr.html#v:uniplate">uniplate</a></code></pre></div></div><h2 id="g:4">Transformations
</h2><div class="top"><p class="src"><a name="v:transform" class="def">transform</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => (on -> on) -> on -> on<a href="src/Data-Generics-UniplateStr.html#transform" class="link">Source</a></p><div class="doc"><p>Transform every element in the tree, in a bottom-up manner.
</p><p>For example, replacing negative literals with literals:
</p><pre> negLits = transform f
where f (Neg (Lit i)) = Lit (negate i)
f x = x
</pre></div></div><div class="top"><p class="src"><a name="v:transformM" class="def">transformM</a> :: (<a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Control-Monad.html#t:Monad">Monad</a> m, <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on) => (on -> m on) -> on -> m on<a href="src/Data-Generics-UniplateStr.html#transformM" class="link">Source</a></p><div class="doc"><p>Monadic variant of <code><a href="Data-Generics-UniplateStr.html#v:transform">transform</a></code>
</p></div></div><div class="top"><p class="src"><a name="v:rewrite" class="def">rewrite</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => (on -> <a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Maybe.html#t:Maybe">Maybe</a> on) -> on -> on<a href="src/Data-Generics-UniplateStr.html#rewrite" class="link">Source</a></p><div class="doc"><p>Rewrite by applying a rule everywhere you can. Ensures that the rule cannot
be applied anywhere in the result:
</p><pre> propRewrite r x = all (isNothing . r) (universe (rewrite r x))
</pre><p>Usually <code><a href="Data-Generics-UniplateStr.html#v:transform">transform</a></code> is more appropriate, but <code><a href="Data-Generics-UniplateStr.html#v:rewrite">rewrite</a></code> can give better
compositionality. Given two single transformations <code>f</code> and <code>g</code>, you can
construct <code>f <code><a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Control-Monad.html#v:mplus">mplus</a></code> g</code> which performs both rewrites until a fixed point.
</p></div></div><div class="top"><p class="src"><a name="v:rewriteM" class="def">rewriteM</a> :: (<a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Control-Monad.html#t:Monad">Monad</a> m, <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on) => (on -> m (<a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Data-Maybe.html#t:Maybe">Maybe</a> on)) -> on -> m on<a href="src/Data-Generics-UniplateStr.html#rewriteM" class="link">Source</a></p><div class="doc"><p>Monadic variant of <code><a href="Data-Generics-UniplateStr.html#v:rewrite">rewrite</a></code>
</p></div></div><div class="top"><p class="src"><a name="v:descend" class="def">descend</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => (on -> on) -> on -> on<a href="src/Data-Generics-UniplateStr.html#descend" class="link">Source</a></p><div class="doc"><p>Perform a transformation on all the immediate children, then combine them back.
This operation allows additional information to be passed downwards, and can be
used to provide a top-down transformation.
</p></div></div><div class="top"><p class="src"><a name="v:descendM" class="def">descendM</a> :: (<a href="/usr/share/doc/ghc/html/libraries/base-4.3.1.0/Control-Monad.html#t:Monad">Monad</a> m, <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on) => (on -> m on) -> on -> m on<a href="src/Data-Generics-UniplateStr.html#descendM" class="link">Source</a></p><div class="doc"><p>Monadic variant of <code><a href="Data-Generics-UniplateStr.html#v:descend">descend</a></code>
</p></div></div><h2 id="g:5">Others
</h2><div class="top"><p class="src"><a name="v:contexts" class="def">contexts</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => on -> [(on, on -> on)]<a href="src/Data-Generics-UniplateStr.html#contexts" class="link">Source</a></p><div class="doc"><p>Return all the contexts and holes.
</p><pre> propUniverse x = universe x == map fst (contexts x)
propId x = all (== x) [b a | (a,b) <- contexts x]
</pre></div></div><div class="top"><p class="src"><a name="v:holes" class="def">holes</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => on -> [(on, on -> on)]<a href="src/Data-Generics-UniplateStr.html#holes" class="link">Source</a></p><div class="doc"><p>The one depth version of <code><a href="Data-Generics-UniplateStr.html#v:contexts">contexts</a></code>
</p><pre> propChildren x = children x == map fst (holes x)
propId x = all (== x) [b a | (a,b) <- holes x]
</pre></div></div><div class="top"><p class="src"><a name="v:para" class="def">para</a> :: <a href="Data-Generics-UniplateStr.html#t:Uniplate">Uniplate</a> on => (on -> [r] -> r) -> on -> r<a href="src/Data-Generics-UniplateStr.html#para" class="link">Source</a></p><div class="doc"><p>Perform a fold-like computation on each value,
technically a paramorphism
</p></div></div><div class="top"><p class="src">module <a href="Data-Generics-Str.html">Data.Generics.Str</a></p></div></div></div><div id="footer"><p>Produced by <a href="http://www.haskell.org/haddock/">Haddock</a> version 2.9.2</p></div></body></html>
