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</script></head><body><div id="package-header"><ul class="links" id="page-menu"><li><a href="src/Control-Lens-Review.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-4.13: Lenses, Folds and Traversals</p></div><div id="content"><div id="module-header"><table class="info"><tr><th>Copyright</th><td>(C) 2012-15 Edward Kmett</td></tr><tr><th>License</th><td>BSD-style (see the file LICENSE)</td></tr><tr><th>Maintainer</th><td>Edward Kmett <ekmett@gmail.com></td></tr><tr><th>Stability</th><td>provisional</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.Review</p></div><div id="table-of-contents"><p class="caption">Contents</p><ul><li><a href="#g:1">Reviewing</a></li></ul></div><div id="description"><p class="caption">Description</p><div class="doc"><p>A <code><a href="Control-Lens-Review.html#t:Review">Review</a></code> is a type-restricted form of a <code><a href="Control-Lens-Type.html#t:Prism">Prism</a></code> that can only be used for
writing back via <code><a href="Control-Lens-Review.html#v:re">re</a></code>, <code><a href="Control-Lens-Review.html#v:review">review</a></code>, <code><a href="Control-Lens-Review.html#v:reuse">reuse</a></code>.</p></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:Review">Review</a> t b = <span class="keyword">forall</span> p f. (<a href="Control-Lens-Prism.html#t:Choice">Choice</a> p, <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> p, <a href="Control-Lens-Internal-Setter.html#t:Settable">Settable</a> f) => <a href="Control-Lens-Type.html#t:Optic-39-">Optic'</a> p f t b</li><li class="src short"><span class="keyword">type</span> <a href="#t:AReview">AReview</a> t b = <a href="Control-Lens-Type.html#t:Optic-39-">Optic'</a> <a href="file:///usr/share/doc/libghc-tagged-doc/html/Data-Tagged.html#t:Tagged">Tagged</a> <a href="Control-Lens-Setter.html#t:Identity">Identity</a> t b</li><li class="src short"><a href="#v:unto">unto</a> :: (<a href="Control-Lens-Iso.html#t:Profunctor">Profunctor</a> p, <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> p, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Functor.html#t:Functor">Functor</a> f) => (b -> t) -> <a href="Control-Lens-Type.html#t:Optic">Optic</a> p f s t a b</li><li class="src short"><a href="#v:un">un</a> :: (<a href="Control-Lens-Iso.html#t:Profunctor">Profunctor</a> p, <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> p, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Functor.html#t:Functor">Functor</a> f) => <a href="Control-Lens-Getter.html#t:Getting">Getting</a> a s a -> <a href="Control-Lens-Type.html#t:Optic-39-">Optic'</a> p f a s</li><li class="src short"><a href="#v:re">re</a> :: <a href="Control-Lens-Getter.html#t:Contravariant">Contravariant</a> f => <a href="Control-Lens-Review.html#t:AReview">AReview</a> t b -> <a href="Control-Lens-Type.html#t:LensLike-39-">LensLike'</a> f b t</li><li class="src short"><a href="#v:review">review</a> :: <a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-Reader-Class.html#t:MonadReader">MonadReader</a> b m => <a href="Control-Lens-Review.html#t:AReview">AReview</a> t b -> m t</li><li class="src short"><a href="#v:reviews">reviews</a> :: <a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-Reader-Class.html#t:MonadReader">MonadReader</a> b m => <a href="Control-Lens-Review.html#t:AReview">AReview</a> t b -> (t -> r) -> m r</li><li class="src short"><a href="#v:reuse">reuse</a> :: <a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-State-Class.html#t:MonadState">MonadState</a> b m => <a href="Control-Lens-Review.html#t:AReview">AReview</a> t b -> m t</li><li class="src short"><a href="#v:reuses">reuses</a> :: <a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-State-Class.html#t:MonadState">MonadState</a> b m => <a href="Control-Lens-Review.html#t:AReview">AReview</a> t b -> (t -> r) -> m r</li><li class="src short"><a href="#v:-35-">(#)</a> :: <a href="Control-Lens-Review.html#t:AReview">AReview</a> t b -> b -> t</li><li class="src short"><span class="keyword">class</span> <a href="#t:Bifunctor">Bifunctor</a> p <span class="keyword">where</span><ul class="subs"><li><a href="#v:bimap">bimap</a> :: (a -> b) -> (c -> d) -> p a c -> p b d</li></ul></li><li class="src short"><a href="#v:retagged">retagged</a> :: (<a href="Control-Lens-Iso.html#t:Profunctor">Profunctor</a> p, <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> p) => p a b -> p s b</li><li class="src short"><span class="keyword">class</span> (<a href="Control-Lens-Iso.html#t:Profunctor">Profunctor</a> p, <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> p) => <a href="#t:Reviewable">Reviewable</a> p</li></ul></div><div id="interface"><h1 id="g:1">Reviewing</h1><div class="top"><p class="src"><span class="keyword">type</span> <a name="t:Review" class="def">Review</a> t b = <span class="keyword">forall</span> p f. (<a href="Control-Lens-Prism.html#t:Choice">Choice</a> p, <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> p, <a href="Control-Lens-Internal-Setter.html#t:Settable">Settable</a> f) => <a href="Control-Lens-Type.html#t:Optic-39-">Optic'</a> p f t b <a href="src/Control-Lens-Type.html#Review" class="link">Source</a></p><div class="doc"><p>This is a limited form of a <code><a href="Control-Lens-Type.html#t:Prism">Prism</a></code> that can only be used for <code>re</code> operations.</p><p>Like with a <code><a href="Control-Lens-Type.html#t:Getter">Getter</a></code>, there are no laws to state for a <code><a href="Control-Lens-Review.html#t:Review">Review</a></code>.</p><p>You can generate a <code><a href="Control-Lens-Review.html#t:Review">Review</a></code> by using <code>unto</code>. You can also use any <code><a href="Control-Lens-Type.html#t:Prism">Prism</a></code> or <code><a href="Control-Lens-Type.html#t:Iso">Iso</a></code>
directly as a <code><a href="Control-Lens-Review.html#t:Review">Review</a></code>.</p></div></div><div class="top"><p class="src"><span class="keyword">type</span> <a name="t:AReview" class="def">AReview</a> t b = <a href="Control-Lens-Type.html#t:Optic-39-">Optic'</a> <a href="file:///usr/share/doc/libghc-tagged-doc/html/Data-Tagged.html#t:Tagged">Tagged</a> <a href="Control-Lens-Setter.html#t:Identity">Identity</a> t b <a href="src/Control-Lens-Type.html#AReview" class="link">Source</a></p><div class="doc"><p>If you see this in a signature for a function, the function is expecting a <code><a href="Control-Lens-Review.html#t:Review">Review</a></code>
(in practice, this usually means a <code><a href="Control-Lens-Type.html#t:Prism">Prism</a></code>).</p></div></div><div class="top"><p class="src"><a name="v:unto" class="def">unto</a> :: (<a href="Control-Lens-Iso.html#t:Profunctor">Profunctor</a> p, <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> p, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Functor.html#t:Functor">Functor</a> f) => (b -> t) -> <a href="Control-Lens-Type.html#t:Optic">Optic</a> p f s t a b <a href="src/Control-Lens-Review.html#unto" class="link">Source</a></p><div class="doc"><p>An analogue of <code><a href="Control-Lens-Getter.html#v:to">to</a></code> for <code><a href="Control-Lens-Review.html#v:review">review</a></code>.</p><pre><code><a href="Control-Lens-Review.html#v:unto">unto</a></code> :: (b -> t) -> <code>Review'</code> t b
</pre><pre><code><a href="Control-Lens-Review.html#v:unto">unto</a></code> = <code><a href="Control-Lens-Review.html#v:un">un</a></code> . <code><a href="Control-Lens-Getter.html#v:to">to</a></code>
</pre></div></div><div class="top"><p class="src"><a name="v:un" class="def">un</a> :: (<a href="Control-Lens-Iso.html#t:Profunctor">Profunctor</a> p, <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> p, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Functor.html#t:Functor">Functor</a> f) => <a href="Control-Lens-Getter.html#t:Getting">Getting</a> a s a -> <a href="Control-Lens-Type.html#t:Optic-39-">Optic'</a> p f a s <a href="src/Control-Lens-Review.html#un" class="link">Source</a></p><div class="doc"><p>Turn a <code><a href="Control-Lens-Type.html#t:Getter">Getter</a></code> around to get a <code><a href="Control-Lens-Review.html#t:Review">Review</a></code></p><pre><code><a href="Control-Lens-Review.html#v:un">un</a></code> = <code><a href="Control-Lens-Review.html#v:unto">unto</a></code> . <code><a href="Control-Lens-Getter.html#v:view">view</a></code>
<code><a href="Control-Lens-Review.html#v:unto">unto</a></code> = <code><a href="Control-Lens-Review.html#v:un">un</a></code> . <code><a href="Control-Lens-Getter.html#v:to">to</a></code>
</pre><pre class="screen"><code class="prompt">>>> </code><strong class="userinput"><code>un (to length) # [1,2,3]
</code></strong>3
</pre></div></div><div class="top"><p class="src"><a name="v:re" class="def">re</a> :: <a href="Control-Lens-Getter.html#t:Contravariant">Contravariant</a> f => <a href="Control-Lens-Review.html#t:AReview">AReview</a> t b -> <a href="Control-Lens-Type.html#t:LensLike-39-">LensLike'</a> f b t <a href="src/Control-Lens-Review.html#re" class="link">Source</a></p><div class="doc"><p>Turn a <code><a href="Control-Lens-Type.html#t:Prism">Prism</a></code> or <code><a href="Control-Lens-Iso.html#v:Iso">Iso</a></code> around to build a <code><a href="Control-Lens-Type.html#t:Getter">Getter</a></code>.</p><p>If you have an <code><a href="Control-Lens-Iso.html#v:Iso">Iso</a></code>, <code><a href="Control-Lens-Iso.html#v:from">from</a></code> is a more powerful version of this function
that will return an <code><a href="Control-Lens-Iso.html#v:Iso">Iso</a></code> instead of a mere <code><a href="Control-Lens-Type.html#t:Getter">Getter</a></code>.</p><pre class="screen"><code class="prompt">>>> </code><strong class="userinput"><code>5 ^.re _Left
</code></strong>Left 5
</pre><pre class="screen"><code class="prompt">>>> </code><strong class="userinput"><code>6 ^.re (_Left.unto succ)
</code></strong>Left 7
</pre><pre><code><a href="Control-Lens-Review.html#v:review">review</a></code> ≡ <code><a href="Control-Lens-Getter.html#v:view">view</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> <code><a href="Control-Lens-Review.html#v:re">re</a></code>
<code><a href="Control-Lens-Review.html#v:reviews">reviews</a></code> ≡ <code><a href="Control-Lens-Getter.html#v:views">views</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> <code><a href="Control-Lens-Review.html#v:re">re</a></code>
<code><a href="Control-Lens-Review.html#v:reuse">reuse</a></code> ≡ <code><a href="Control-Lens-Getter.html#v:use">use</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> <code><a href="Control-Lens-Review.html#v:re">re</a></code>
<code><a href="Control-Lens-Review.html#v:reuses">reuses</a></code> ≡ <code><a href="Control-Lens-Getter.html#v:uses">uses</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> <code><a href="Control-Lens-Review.html#v:re">re</a></code>
</pre><pre><code><a href="Control-Lens-Review.html#v:re">re</a></code> :: <code><a href="Control-Lens-Type.html#t:Prism">Prism</a></code> s t a b -> <code><a href="Control-Lens-Type.html#t:Getter">Getter</a></code> b t
<code><a href="Control-Lens-Review.html#v:re">re</a></code> :: <code><a href="Control-Lens-Type.html#t:Iso">Iso</a></code> s t a b -> <code><a href="Control-Lens-Type.html#t:Getter">Getter</a></code> b t
</pre></div></div><div class="top"><p class="src"><a name="v:review" class="def">review</a> :: <a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-Reader-Class.html#t:MonadReader">MonadReader</a> b m => <a href="Control-Lens-Review.html#t:AReview">AReview</a> t b -> m t <a href="src/Control-Lens-Review.html#review" class="link">Source</a></p><div class="doc"><p>This can be used to turn an <code><a href="Control-Lens-Iso.html#v:Iso">Iso</a></code> or <code><a href="Control-Lens-Type.html#t:Prism">Prism</a></code> around and <code><a href="Control-Lens-Getter.html#v:view">view</a></code> a value (or the current environment) through it the other way.</p><pre><code><a href="Control-Lens-Review.html#v:review">review</a></code> ≡ <code><a href="Control-Lens-Getter.html#v:view">view</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> <code><a href="Control-Lens-Review.html#v:re">re</a></code>
<code><a href="Control-Lens-Review.html#v:review">review</a></code> . <code><a href="Control-Lens-Review.html#v:unto">unto</a></code> ≡ <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:id">id</a></code>
</pre><pre class="screen"><code class="prompt">>>> </code><strong class="userinput"><code>review _Left "mustard"
</code></strong>Left "mustard"
</pre><pre class="screen"><code class="prompt">>>> </code><strong class="userinput"><code>review (unto succ) 5
</code></strong>6
</pre><p>Usually <code><a href="Control-Lens-Review.html#v:review">review</a></code> is used in the <code>(->)</code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Control-Monad.html#t:Monad">Monad</a></code> with a <code><a href="Control-Lens-Type.html#t:Prism">Prism</a></code> or <code><a href="Control-Lens-Iso.html#v:Iso">Iso</a></code>, in which case it may be useful to think of
it as having one of these more restricted type signatures:</p><pre><code><a href="Control-Lens-Review.html#v:review">review</a></code> :: <code><a href="Control-Lens-Type.html#t:Iso-39-">Iso'</a></code> s a -> a -> s
<code><a href="Control-Lens-Review.html#v:review">review</a></code> :: <code><a href="Control-Lens-Type.html#t:Prism-39-">Prism'</a></code> s a -> a -> s
</pre><p>However, when working with a <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Control-Monad.html#t:Monad">Monad</a></code> transformer stack, it is sometimes useful to be able to <code><a href="Control-Lens-Review.html#v:review">review</a></code> the current environment, in which case
it may be beneficial to think of it as having one of these slightly more liberal type signatures:</p><pre><code><a href="Control-Lens-Review.html#v:review">review</a></code> :: <code><a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-Reader-Class.html#t:MonadReader">MonadReader</a></code> a m => <code><a href="Control-Lens-Type.html#t:Iso-39-">Iso'</a></code> s a -> m s
<code><a href="Control-Lens-Review.html#v:review">review</a></code> :: <code><a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-Reader-Class.html#t:MonadReader">MonadReader</a></code> a m => <code><a href="Control-Lens-Type.html#t:Prism-39-">Prism'</a></code> s a -> m s
</pre></div></div><div class="top"><p class="src"><a name="v:reviews" class="def">reviews</a> :: <a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-Reader-Class.html#t:MonadReader">MonadReader</a> b m => <a href="Control-Lens-Review.html#t:AReview">AReview</a> t b -> (t -> r) -> m r <a href="src/Control-Lens-Review.html#reviews" class="link">Source</a></p><div class="doc"><p>This can be used to turn an <code><a href="Control-Lens-Iso.html#v:Iso">Iso</a></code> or <code><a href="Control-Lens-Type.html#t:Prism">Prism</a></code> around and <code><a href="Control-Lens-Getter.html#v:view">view</a></code> a value (or the current environment) through it the other way,
applying a function.</p><pre><code><a href="Control-Lens-Review.html#v:reviews">reviews</a></code> ≡ <code><a href="Control-Lens-Getter.html#v:views">views</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> <code><a href="Control-Lens-Review.html#v:re">re</a></code>
<code><a href="Control-Lens-Review.html#v:reviews">reviews</a></code> (<code><a href="Control-Lens-Review.html#v:unto">unto</a></code> f) g ≡ g <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> f
</pre><pre class="screen"><code class="prompt">>>> </code><strong class="userinput"><code>reviews _Left isRight "mustard"
</code></strong>False
</pre><pre class="screen"><code class="prompt">>>> </code><strong class="userinput"><code>reviews (unto succ) (*2) 3
</code></strong>8
</pre><p>Usually this function is used in the <code>(->)</code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Control-Monad.html#t:Monad">Monad</a></code> with a <code><a href="Control-Lens-Type.html#t:Prism">Prism</a></code> or <code><a href="Control-Lens-Iso.html#v:Iso">Iso</a></code>, in which case it may be useful to think of
it as having one of these more restricted type signatures:</p><pre><code><a href="Control-Lens-Review.html#v:reviews">reviews</a></code> :: <code><a href="Control-Lens-Type.html#t:Iso-39-">Iso'</a></code> s a -> (s -> r) -> a -> r
<code><a href="Control-Lens-Review.html#v:reviews">reviews</a></code> :: <code><a href="Control-Lens-Type.html#t:Prism-39-">Prism'</a></code> s a -> (s -> r) -> a -> r
</pre><p>However, when working with a <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Control-Monad.html#t:Monad">Monad</a></code> transformer stack, it is sometimes useful to be able to <code><a href="Control-Lens-Review.html#v:review">review</a></code> the current environment, in which case
it may be beneficial to think of it as having one of these slightly more liberal type signatures:</p><pre><code><a href="Control-Lens-Review.html#v:reviews">reviews</a></code> :: <code><a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-Reader-Class.html#t:MonadReader">MonadReader</a></code> a m => <code><a href="Control-Lens-Type.html#t:Iso-39-">Iso'</a></code> s a -> (s -> r) -> m r
<code><a href="Control-Lens-Review.html#v:reviews">reviews</a></code> :: <code><a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-Reader-Class.html#t:MonadReader">MonadReader</a></code> a m => <code><a href="Control-Lens-Type.html#t:Prism-39-">Prism'</a></code> s a -> (s -> r) -> m r
</pre></div></div><div class="top"><p class="src"><a name="v:reuse" class="def">reuse</a> :: <a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-State-Class.html#t:MonadState">MonadState</a> b m => <a href="Control-Lens-Review.html#t:AReview">AReview</a> t b -> m t <a href="src/Control-Lens-Review.html#reuse" class="link">Source</a></p><div class="doc"><p>This can be used to turn an <code><a href="Control-Lens-Iso.html#v:Iso">Iso</a></code> or <code><a href="Control-Lens-Type.html#t:Prism">Prism</a></code> around and <code><a href="Control-Lens-Getter.html#v:use">use</a></code> a value (or the current environment) through it the other way.</p><pre><code><a href="Control-Lens-Review.html#v:reuse">reuse</a></code> ≡ <code><a href="Control-Lens-Getter.html#v:use">use</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> <code><a href="Control-Lens-Review.html#v:re">re</a></code>
<code><a href="Control-Lens-Review.html#v:reuse">reuse</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> <code><a href="Control-Lens-Review.html#v:unto">unto</a></code> ≡ <code><a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-State-Class.html#v:gets">gets</a></code>
</pre><pre class="screen"><code class="prompt">>>> </code><strong class="userinput"><code>evalState (reuse _Left) 5
</code></strong>Left 5
</pre><pre class="screen"><code class="prompt">>>> </code><strong class="userinput"><code>evalState (reuse (unto succ)) 5
</code></strong>6
</pre><pre><code><a href="Control-Lens-Review.html#v:reuse">reuse</a></code> :: <code><a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-State-Class.html#t:MonadState">MonadState</a></code> a m => <code><a href="Control-Lens-Type.html#t:Prism-39-">Prism'</a></code> s a -> m s
<code><a href="Control-Lens-Review.html#v:reuse">reuse</a></code> :: <code><a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-State-Class.html#t:MonadState">MonadState</a></code> a m => <code><a href="Control-Lens-Type.html#t:Iso-39-">Iso'</a></code> s a -> m s
</pre></div></div><div class="top"><p class="src"><a name="v:reuses" class="def">reuses</a> :: <a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-State-Class.html#t:MonadState">MonadState</a> b m => <a href="Control-Lens-Review.html#t:AReview">AReview</a> t b -> (t -> r) -> m r <a href="src/Control-Lens-Review.html#reuses" class="link">Source</a></p><div class="doc"><p>This can be used to turn an <code><a href="Control-Lens-Iso.html#v:Iso">Iso</a></code> or <code><a href="Control-Lens-Type.html#t:Prism">Prism</a></code> around and <code><a href="Control-Lens-Getter.html#v:use">use</a></code> the current state through it the other way,
applying a function.</p><pre><code><a href="Control-Lens-Review.html#v:reuses">reuses</a></code> ≡ <code><a href="Control-Lens-Getter.html#v:uses">uses</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> <code><a href="Control-Lens-Review.html#v:re">re</a></code>
<code><a href="Control-Lens-Review.html#v:reuses">reuses</a></code> (<code><a href="Control-Lens-Review.html#v:unto">unto</a></code> f) g ≡ <code><a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-State-Class.html#v:gets">gets</a></code> (g <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> f)
</pre><pre class="screen"><code class="prompt">>>> </code><strong class="userinput"><code>evalState (reuses _Left isLeft) (5 :: Int)
</code></strong>True
</pre><pre><code><a href="Control-Lens-Review.html#v:reuses">reuses</a></code> :: <code><a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-State-Class.html#t:MonadState">MonadState</a></code> a m => <code><a href="Control-Lens-Type.html#t:Prism-39-">Prism'</a></code> s a -> (s -> r) -> m r
<code><a href="Control-Lens-Review.html#v:reuses">reuses</a></code> :: <code><a href="file:///usr/share/doc/libghc-mtl-doc/html/Control-Monad-State-Class.html#t:MonadState">MonadState</a></code> a m => <code><a href="Control-Lens-Type.html#t:Iso-39-">Iso'</a></code> s a -> (s -> r) -> m r
</pre></div></div><div class="top"><p class="src"><a name="v:-35-" class="def">(#)</a> :: <a href="Control-Lens-Review.html#t:AReview">AReview</a> t b -> b -> t <span class="fixity">infixr 8</span><span class="rightedge"></span> <a href="src/Control-Lens-Review.html#%23" class="link">Source</a></p><div class="doc"><p>An infix alias for <code><a href="Control-Lens-Review.html#v:review">review</a></code>.</p><pre><code><a href="Control-Lens-Review.html#v:unto">unto</a></code> f # x ≡ f x
l # x ≡ x <code><a href="Control-Lens-Getter.html#v:-94-.">^.</a></code> <code><a href="Control-Lens-Review.html#v:re">re</a></code> l
</pre><p>This is commonly used when using a <code><a href="Control-Lens-Type.html#t:Prism">Prism</a></code> as a smart constructor.</p><pre class="screen"><code class="prompt">>>> </code><strong class="userinput"><code>_Left # 4
</code></strong>Left 4
</pre><p>But it can be used for any <code><a href="Control-Lens-Type.html#t:Prism">Prism</a></code></p><pre class="screen"><code class="prompt">>>> </code><strong class="userinput"><code>base 16 # 123
</code></strong>"7b"
</pre><pre>(#) :: <code><a href="Control-Lens-Type.html#t:Iso-39-">Iso'</a></code> s a -> a -> s
(#) :: <code><a href="Control-Lens-Type.html#t:Prism-39-">Prism'</a></code> s a -> a -> s
(#) :: <code><a href="Control-Lens-Review.html#t:Review">Review</a></code> s a -> a -> s
(#) :: <code><a href="Control-Lens-Type.html#t:Equality-39-">Equality'</a></code> s a -> a -> s
</pre></div></div><div class="top"><p class="src"><span class="keyword">class</span> <a name="t:Bifunctor" class="def">Bifunctor</a> p <span class="keyword">where</span></p><div class="doc"><p>Formally, the class <code><a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a></code> represents a bifunctor
from <code>Hask</code> -> <code>Hask</code>.</p><p>Intuitively it is a bifunctor where both the first and second
arguments are covariant.</p><p>You can define a <code><a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a></code> by either defining <code><a href="Control-Lens-Review.html#v:bimap">bimap</a></code> or by
defining both <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:first">first</a></code> and <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:second">second</a></code>.</p><p>If you supply <code><a href="Control-Lens-Review.html#v:bimap">bimap</a></code>, you should ensure that:</p><pre><code><a href="Control-Lens-Review.html#v:bimap">bimap</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:id">id</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:id">id</a></code> ≡ <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:id">id</a></code></pre><p>If you supply <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:first">first</a></code> and <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:second">second</a></code>, ensure:</p><pre><code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:first">first</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:id">id</a></code> ≡ <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:id">id</a></code>
<code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:second">second</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:id">id</a></code> ≡ <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:id">id</a></code>
</pre><p>If you supply both, you should also ensure:</p><pre><code><a href="Control-Lens-Review.html#v:bimap">bimap</a></code> f g ≡ <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:first">first</a></code> f <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:second">second</a></code> g</pre><p>These ensure by parametricity:</p><pre><code><a href="Control-Lens-Review.html#v:bimap">bimap</a></code> (f <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> g) (h <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> i) ≡ <code><a href="Control-Lens-Review.html#v:bimap">bimap</a></code> f h <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> <code><a href="Control-Lens-Review.html#v:bimap">bimap</a></code> g i
<code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:first">first</a></code> (f <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> g) ≡ <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:first">first</a></code> f <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:first">first</a></code> g
<code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:second">second</a></code> (f <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> g) ≡ <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:second">second</a></code> f <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:second">second</a></code> g
</pre><p><em>Since: 4.8.0.0</em></p></div><div class="subs minimal"><p class="caption">Minimal complete definition</p><p class="src"><a href="Control-Lens-Review.html#v:bimap">bimap</a> | <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:first">first</a>, <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:second">second</a></p></div><div class="subs methods"><p class="caption">Methods</p><p class="src"><a name="v:bimap" class="def">bimap</a> :: (a -> b) -> (c -> d) -> p a c -> p b d</p><div class="doc"><p>Map over both arguments at the same time.</p><pre><code><a href="Control-Lens-Review.html#v:bimap">bimap</a></code> f g ≡ <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:first">first</a></code> f <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Function.html#v:.">.</a></code> <code><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Bifunctor.html#v:second">second</a></code> g</pre></div></div><div class="subs instances"><p id="control.i:Bifunctor" class="caption collapser" onclick="toggleSection('i:Bifunctor')">Instances</p><div id="section.i:Bifunctor" class="show"><table><tr><td class="src clearfix"><span class="inst-left"><a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> <a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Either.html#t:Either">Either</a></span></td><td class="doc empty"> </td></tr><tr><td class="src clearfix"><span class="inst-left"><a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> <a href="file:///usr/share/doc/ghc-doc/html/libraries/ghc-prim-0.4.0.0/GHC-Tuple.html#t:-40--44--41-">(,)</a></span></td><td class="doc empty"> </td></tr><tr><td class="src clearfix"><span class="inst-left"><a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> <a href="Control-Lens-Getter.html#t:Const">Const</a></span></td><td class="doc empty"> </td></tr><tr><td class="src clearfix"><span class="inst-left"><a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> <a href="file:///usr/share/doc/libghc-semigroups-doc/html/Data-Semigroup.html#t:Arg">Arg</a></span></td><td class="doc empty"> </td></tr><tr><td class="src clearfix"><span class="inst-left"><a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/ghc-prim-0.4.0.0/GHC-Tuple.html#t:-40--44--44--41-">(,,)</a> x1)</span></td><td class="doc empty"> </td></tr><tr><td class="src clearfix"><span class="inst-left"><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Functor.html#t:Functor">Functor</a> g => <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> (<a href="file:///usr/share/doc/libghc-bifunctors-doc/html/Data-Bifunctor-Joker.html#t:Joker">Joker</a> g)</span></td><td class="doc empty"> </td></tr><tr><td class="src clearfix"><span class="inst-left"><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Functor.html#t:Functor">Functor</a> f => <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> (<a href="file:///usr/share/doc/libghc-bifunctors-doc/html/Data-Bifunctor-Clown.html#t:Clown">Clown</a> f)</span></td><td class="doc empty"> </td></tr><tr><td class="src clearfix"><span class="inst-left"><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Functor.html#t:Functor">Functor</a> f => <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> (<a href="file:///usr/share/doc/libghc-free-doc/html/Control-Comonad-Trans-Cofree.html#t:CofreeF">CofreeF</a> f)</span></td><td class="doc empty"> </td></tr><tr><td class="src clearfix"><span class="inst-left"><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Functor.html#t:Functor">Functor</a> f => <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> (<a href="file:///usr/share/doc/libghc-free-doc/html/Control-Monad-Trans-Free.html#t:FreeF">FreeF</a> f)</span></td><td class="doc empty"> </td></tr><tr><td class="src clearfix"><span class="inst-left"><a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> (<a href="file:///usr/share/doc/libghc-tagged-doc/html/Data-Tagged.html#t:Tagged">Tagged</a> *)</span></td><td class="doc empty"> </td></tr><tr><td class="src clearfix"><span class="inst-left"><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Functor.html#t:Functor">Functor</a> f => <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> (<a href="Control-Lens-Internal-Getter.html#t:AlongsideRight">AlongsideRight</a> f)</span></td><td class="doc empty"> </td></tr><tr><td class="src clearfix"><span class="inst-left"><a href="file:///usr/share/doc/ghc-doc/html/libraries/base-4.8.2.0/Data-Functor.html#t:Functor">Functor</a> f => <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> (<a href="Control-Lens-Internal-Getter.html#t:AlongsideLeft">AlongsideLeft</a> f)</span></td><td class="doc empty"> </td></tr><tr><td class="src clearfix"><span class="inst-left"><a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/ghc-prim-0.4.0.0/GHC-Tuple.html#t:-40--44--44--44--41-">(,,,)</a> x1 x2)</span></td><td class="doc empty"> </td></tr><tr><td class="src clearfix"><span class="inst-left"><a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/ghc-prim-0.4.0.0/GHC-Tuple.html#t:-40--44--44--44--44--41-">(,,,,)</a> x1 x2 x3)</span></td><td class="doc empty"> </td></tr><tr><td class="src clearfix"><span class="inst-left"><a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/ghc-prim-0.4.0.0/GHC-Tuple.html#t:-40--44--44--44--44--44--41-">(,,,,,)</a> x1 x2 x3 x4)</span></td><td class="doc empty"> </td></tr><tr><td class="src clearfix"><span class="inst-left"><a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> (<a href="file:///usr/share/doc/ghc-doc/html/libraries/ghc-prim-0.4.0.0/GHC-Tuple.html#t:-40--44--44--44--44--44--44--41-">(,,,,,,)</a> x1 x2 x3 x4 x5)</span></td><td class="doc empty"> </td></tr></table></div></div></div><div class="top"><p class="src"><a name="v:retagged" class="def">retagged</a> :: (<a href="Control-Lens-Iso.html#t:Profunctor">Profunctor</a> p, <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> p) => p a b -> p s b <a href="src/Control-Lens-Internal-Review.html#retagged" class="link">Source</a></p><div class="doc"><p>This is a profunctor used internally to implement <a href="Review.html">Review</a></p><p>It plays a role similar to that of <code><a href="Control-Lens-Internal-Getter.html#v:Accessor">Accessor</a></code>
or <code>Const</code> do for <a href="Control-Lens-Getter.html">Control.Lens.Getter</a></p></div></div><div class="top"><p class="src"><span class="keyword">class</span> (<a href="Control-Lens-Iso.html#t:Profunctor">Profunctor</a> p, <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> p) => <a name="t:Reviewable" class="def">Reviewable</a> p <a href="src/Control-Lens-Internal-Review.html#Reviewable" class="link">Source</a></p><div class="doc"><p>This class is provided mostly for backwards compatibility with lens 3.8,
but it can also shorten type signatures.</p></div><div class="subs instances"><p id="control.i:Reviewable" class="caption collapser" onclick="toggleSection('i:Reviewable')">Instances</p><div id="section.i:Reviewable" class="show"><table><tr><td class="src clearfix"><span class="inst-left">(<a href="Control-Lens-Iso.html#t:Profunctor">Profunctor</a> p, <a href="Control-Lens-Review.html#t:Bifunctor">Bifunctor</a> p) => <a href="Control-Lens-Review.html#t:Reviewable">Reviewable</a> p</span> <a href="src/Control-Lens-Internal-Review.html#line-31" class="link">Source</a></td><td class="doc empty"> </td></tr></table></div></div></div></div></div><div id="footer"><p>Produced by <a href="http://www.haskell.org/haddock/">Haddock</a> version 2.16.1</p></div></body></html>
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