<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Data.Generics.Uniplate.Direct</title><link href="ocean.css" rel="stylesheet" type="text/css" title="Ocean" /><script src="haddock-util.js" type="text/javascript"></script><script type="text/javascript">//<![CDATA[
window.onload = function () {pageLoad();setSynopsis("mini_Data-Generics-Uniplate-Direct.html");};
//]]>
</script></head><body><div id="package-header"><ul class="links" id="page-menu"><li><a href="src/Data-Generics-Uniplate-Direct.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.Uniplate.Direct</p></div><div id="table-of-contents"><p class="caption">Contents</p><ul><li><a href="#g:1">The Combinators
</a></li></ul></div><div id="description"><p class="caption">Description</p><div class="doc"><p>This module supplies a method for writing <code><a href="Data-Generics-Uniplate-Operations.html#t:Uniplate">Uniplate</a></code> and <code><a href="Data-Generics-Uniplate-Operations.html#t:Biplate">Biplate</a></code> instances.
This moulde gives the highest performance, but requires many instance definitions. The
instances can be generated using Derive: <a href="http://community.haskell.org/~ndm/derive/">http://community.haskell.org/~ndm/derive/</a>.
</p><p>To take an example:
</p><pre> data Expr = Var Int | Pos Expr String | Neg Expr | Add Expr Expr
data Stmt = Seq [Stmt] | Sel [Expr] | Let String Expr
instance Uniplate Expr where
uniplate (Var x ) = plate Var |- x
uniplate (Pos x y) = plate Pos |* x |- y
uniplate (Neg x ) = plate Neg |* x
uniplate (Add x y) = plate Add |* x |* y
instance Biplate Expr Expr where
biplate = plateSelf
instance Uniplate Stmt where
uniplate (Seq x ) = plate Seq ||* x
uniplate (Sel x ) = plate Sel ||+ x
uniplate (Let x y) = plate Let |- x |- y
instance Biplate Stmt Stmt where
biplate = plateSelf
instance Biplate Stmt Expr where
biplate (Seq x ) = plate Seq ||+ x
biplate (Sel x ) = plate Sel ||* x
biplate (Let x y) = plate Let |- x |* y
</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">module <a href="Data-Generics-Uniplate-Operations.html">Data.Generics.Uniplate.Operations</a></li><li class="src short"><a href="#v:plate">plate</a> :: from -> Type from to</li><li class="src short"><a href="#v:plateSelf">plateSelf</a> :: to -> Type to to</li><li class="src short"><a href="#v:-124--43-">(|+)</a> :: <a href="Data-Generics-Uniplate-Operations.html#t:Biplate">Biplate</a> item to => Type (item -> from) to -> item -> Type from to</li><li class="src short"><a href="#v:-124--45-">(|-)</a> :: Type (item -> from) to -> item -> Type from to</li><li class="src short"><a href="#v:-124--42-">(|*)</a> :: Type (to -> from) to -> to -> Type from to</li><li class="src short"><a href="#v:-124--124--43-">(||+)</a> :: <a href="Data-Generics-Uniplate-Operations.html#t:Biplate">Biplate</a> item to => Type ([item] -> from) to -> [item] -> Type from to</li><li class="src short"><a href="#v:-124--124--42-">(||*)</a> :: Type ([to] -> from) to -> [to] -> Type from to</li><li class="src short"><a href="#v:plateProject">plateProject</a> :: <a href="Data-Generics-Uniplate-Operations.html#t:Biplate">Biplate</a> item to => (from -> item) -> (item -> from) -> from -> Type from to</li></ul></div><div id="interface"><h1>Documentation</h1><div class="top"><p class="src">module <a href="Data-Generics-Uniplate-Operations.html">Data.Generics.Uniplate.Operations</a></p></div><h1 id="g:1">The Combinators
</h1><div class="top"><p class="src"><a name="v:plate" class="def">plate</a> :: from -> Type from to<a href="src/Data-Generics-Uniplate-Direct.html#plate" class="link">Source</a></p><div class="doc"><p>The main combinator used to start the chain.
</p><p>The following rule can be used for optimisation:
</p><pre> plate Ctor |- x == plate (Ctor x)
</pre></div></div><div class="top"><p class="src"><a name="v:plateSelf" class="def">plateSelf</a> :: to -> Type to to<a href="src/Data-Generics-Uniplate-Direct.html#plateSelf" class="link">Source</a></p><div class="doc"><p>Used for <code><a href="Data-Generics-Uniplate-Operations.html#t:Biplate">Biplate</a></code> definitions where both types are the same.
</p></div></div><div class="top"><p class="src"><a name="v:-124--43-" class="def">(|+)</a> :: <a href="Data-Generics-Uniplate-Operations.html#t:Biplate">Biplate</a> item to => Type (item -> from) to -> item -> Type from to<a href="src/Data-Generics-Uniplate-Direct.html#%7C%2B" class="link">Source</a></p><div class="doc"><p>The field to the right may contain the target.
</p></div></div><div class="top"><p class="src"><a name="v:-124--45-" class="def">(|-)</a> :: Type (item -> from) to -> item -> Type from to<a href="src/Data-Generics-Uniplate-Direct.html#%7C-" class="link">Source</a></p><div class="doc"><p>The field to the right <em>does not</em> contain the target.
</p></div></div><div class="top"><p class="src"><a name="v:-124--42-" class="def">(|*)</a> :: Type (to -> from) to -> to -> Type from to<a href="src/Data-Generics-Uniplate-Direct.html#%7C%2A" class="link">Source</a></p><div class="doc"><p>The field to the right is the target.
</p></div></div><div class="top"><p class="src"><a name="v:-124--124--43-" class="def">(||+)</a> :: <a href="Data-Generics-Uniplate-Operations.html#t:Biplate">Biplate</a> item to => Type ([item] -> from) to -> [item] -> Type from to<a href="src/Data-Generics-Uniplate-Direct.html#%7C%7C%2B" class="link">Source</a></p><div class="doc"><p>The field to the right is a list of types which may contain the target
</p></div></div><div class="top"><p class="src"><a name="v:-124--124--42-" class="def">(||*)</a> :: Type ([to] -> from) to -> [to] -> Type from to<a href="src/Data-Generics-Uniplate-Direct.html#%7C%7C%2A" class="link">Source</a></p><div class="doc"><p>The field to the right is a list of the type of the target
</p></div></div><div class="top"><p class="src"><a name="v:plateProject" class="def">plateProject</a> :: <a href="Data-Generics-Uniplate-Operations.html#t:Biplate">Biplate</a> item to => (from -> item) -> (item -> from) -> from -> Type from to<a href="src/Data-Generics-Uniplate-Direct.html#plateProject" class="link">Source</a></p><div class="doc"><p>Write an instance in terms of a projection/injection pair. Usually used to define instances
for abstract containers such as Map:
</p><pre> instance Biplate (Map.Map [Char] Int) Int where
biplate = plateProject Map.toAscList Map.fromDistinctAscList
</pre><p>Because we know that Uniplate operations will not change the keys,
we can use the <code>fromDistictAscList</code> function to reconstruct it.
</p></div></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>
