/usr/share/doc/libghc-lens-doc/html/Control-Lens.html

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</script></head><body><div id="package-header"><ul class="links" id="page-menu"><li><a href="src/Control-Lens.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">lens-4.15.4: Lenses, Folds and Traversals</p></div><div id="content"><div id="module-header"><table class="info"><tr><th valign="top">Copyright</th><td>(C) 2012-16 Edward Kmett</td></tr><tr><th>License</th><td>BSD-style (see the file LICENSE)</td></tr><tr><th>Maintainer</th><td>Edward Kmett &lt;ekmett@gmail.com&gt;</td></tr><tr><th>Stability</th><td>experimental</td></tr><tr><th>Portability</th><td>non-portable</td></tr><tr><th>Safe Haskell</th><td>Safe</td></tr><tr><th>Language</th><td>Haskell98</td></tr></table><p class="caption">Control.Lens</p></div><div id="description"><p class="caption">Description</p><div class="doc"><p>Usage:</p><p>You can derive lenses automatically for many data types:</p><pre>import Control.Lens

data FooBar a
  = Foo { _x :: [<code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a></code>], _y :: a }
  | Bar { _x :: [<code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a></code>] }
<code><a href="Control-Lens-TH.html#v:makeLenses">makeLenses</a></code> ''FooBar
</pre><p>This defines the following lenses:</p><pre>x :: <code><a href="Control-Lens-Type.html#t:Lens-39-">Lens'</a></code> (FooBar a) [<code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.9.1.0/Data-Int.html#t:Int">Int</a></code>]
y :: <code><a href="Control-Lens-Type.html#t:Traversal">Traversal</a></code> (FooBar a) (FooBar b) a b
</pre><p>You can then access the value of <code>_x</code> with (<code><a href="Control-Lens-Getter.html#v:-94-.">^.</a></code>), the value of <code>_y</code> &#8211;
 with (<code><a href="Control-Lens-Fold.html#v:-94--63-">^?</a></code>) or (<code><a href="Control-Lens-Fold.html#v:-94--63--33-">^?!</a></code>) (since it can fail), set the values with (<code><a href="Control-Lens-Setter.html#v:.-126-">.~</a></code>),
 modify them with (<code><a href="Control-Lens-Setter.html#v:-37--126-">%~</a></code>), and use almost any other combinator that is
 re-exported here on those fields.</p><p>The combinators here have unusually specific type signatures, so for
 particularly tricky ones, the simpler type signatures you might want to
 pretend the combinators have are specified as well.</p><p>More information on how to use lenses is available on the lens wiki:</p><p><a href="http://github.com/ekmett/lens/wiki">http://github.com/ekmett/lens/wiki</a></p><p><img src="Hierarchy.png" /></p></div></div><div id="interface"><h1>Documentation</h1><div class="top"><p class="src">module <a href="Control-Lens-At.html">Control.Lens.At</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Cons.html">Control.Lens.Cons</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Each.html">Control.Lens.Each</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Empty.html">Control.Lens.Empty</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Equality.html">Control.Lens.Equality</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Fold.html">Control.Lens.Fold</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Getter.html">Control.Lens.Getter</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Indexed.html">Control.Lens.Indexed</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Iso.html">Control.Lens.Iso</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Lens.html">Control.Lens.Lens</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Level.html">Control.Lens.Level</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Plated.html">Control.Lens.Plated</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Prism.html">Control.Lens.Prism</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Reified.html">Control.Lens.Reified</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Review.html">Control.Lens.Review</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Setter.html">Control.Lens.Setter</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-TH.html">Control.Lens.TH</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Traversal.html">Control.Lens.Traversal</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Tuple.html">Control.Lens.Tuple</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Type.html">Control.Lens.Type</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Wrapped.html">Control.Lens.Wrapped</a></p></div><div class="top"><p class="src">module <a href="Control-Lens-Zoom.html">Control.Lens.Zoom</a></p></div></div></div><div id="footer"><p>Produced by <a href="http://www.haskell.org/haddock/">Haddock</a> version 2.17.3</p></div></body></html>
libghc-lens-doc 4.15.4-1 / usr / share / doc / libghc-lens-doc / html / Control-Lens.html
