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<title>XMonad/Util/Invisible.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE GeneralizedNewtypeDeriving #-}</span>
<a name="line-2"></a>
<a name="line-3"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-4"></a><span class='hs-comment'>-- |</span>
<a name="line-5"></a><span class='hs-comment'>-- Module : XMonad.Util.Invisible</span>
<a name="line-6"></a><span class='hs-comment'>-- Copyright : (c) 2007 Andrea Rossato, David Roundy</span>
<a name="line-7"></a><span class='hs-comment'>-- License : BSD-style (see xmonad/LICENSE)</span>
<a name="line-8"></a><span class='hs-comment'>--</span>
<a name="line-9"></a><span class='hs-comment'>-- Maintainer : andrea.rossato@unibz.it</span>
<a name="line-10"></a><span class='hs-comment'>-- Stability : unstable</span>
<a name="line-11"></a><span class='hs-comment'>-- Portability : unportable</span>
<a name="line-12"></a><span class='hs-comment'>--</span>
<a name="line-13"></a><span class='hs-comment'>-- A data type to store the layout state</span>
<a name="line-14"></a><span class='hs-comment'>--</span>
<a name="line-15"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
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<a name="line-17"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>XMonad</span><span class='hs-varop'>.</span><span class='hs-conid'>Util</span><span class='hs-varop'>.</span><span class='hs-conid'>Invisible</span> <span class='hs-layout'>(</span>
<a name="line-18"></a> <span class='hs-comment'>-- * Usage:</span>
<a name="line-19"></a> <span class='hs-comment'>-- $usage</span>
<a name="line-20"></a> <span class='hs-conid'>Invisible</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-21"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>whenIJust</span>
<a name="line-22"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>fromIMaybe</span>
<a name="line-23"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-24"></a>
<a name="line-25"></a><span class='hs-comment'>-- $usage</span>
<a name="line-26"></a><span class='hs-comment'>-- A wrapper data type to store layout state that shouldn't be persisted across</span>
<a name="line-27"></a><span class='hs-comment'>-- restarts. A common wrapped type to use is @Maybe a@.</span>
<a name="line-28"></a><span class='hs-comment'>-- Invisible derives trivial definitions for Read and Show, so the wrapped data</span>
<a name="line-29"></a><span class='hs-comment'>-- type need not do so.</span>
<a name="line-30"></a>
<a name="line-31"></a><a name="Invisible"></a><span class='hs-keyword'>newtype</span> <span class='hs-conid'>Invisible</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>I</span> <span class='hs-layout'>(</span><span class='hs-varid'>m</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>deriving</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monad</span><span class='hs-layout'>,</span> <span class='hs-conid'>Functor</span><span class='hs-layout'>)</span>
<a name="line-32"></a>
<a name="line-33"></a><a name="instance%20Read%20(Invisible%20m%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>Functor</span> <span class='hs-varid'>m</span><span class='hs-layout'>,</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Read</span> <span class='hs-layout'>(</span><span class='hs-conid'>Invisible</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-34"></a> <span class='hs-varid'>readsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyglyph'>[</span><span class='hs-layout'>(</span><span class='hs-varid'>fail</span> <span class='hs-str'>"Read Invisible"</span><span class='hs-layout'>,</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span><span class='hs-keyglyph'>]</span>
<a name="line-35"></a>
<a name="line-36"></a><a name="instance%20Show%20(Invisible%20m%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Show</span> <span class='hs-layout'>(</span><span class='hs-conid'>Invisible</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-37"></a> <span class='hs-varid'>show</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-str'>""</span>
<a name="line-38"></a>
<a name="line-39"></a><a name="whenIJust"></a><span class='hs-definition'>whenIJust</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Invisible</span> <span class='hs-conid'>Maybe</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-conid'>()</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-conid'>()</span>
<a name="line-40"></a><span class='hs-definition'>whenIJust</span> <span class='hs-layout'>(</span><span class='hs-conid'>I</span> <span class='hs-layout'>(</span><span class='hs-conid'>Just</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>f</span> <span class='hs-varid'>x</span>
<a name="line-41"></a><span class='hs-definition'>whenIJust</span> <span class='hs-layout'>(</span><span class='hs-conid'>I</span> <span class='hs-conid'>Nothing</span><span class='hs-layout'>)</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>return</span> <span class='hs-conid'>()</span>
<a name="line-42"></a>
<a name="line-43"></a><a name="fromIMaybe"></a><span class='hs-definition'>fromIMaybe</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Invisible</span> <span class='hs-conid'>Maybe</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span>
<a name="line-44"></a><span class='hs-definition'>fromIMaybe</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>I</span> <span class='hs-layout'>(</span><span class='hs-conid'>Just</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>x</span>
<a name="line-45"></a><span class='hs-definition'>fromIMaybe</span> <span class='hs-varid'>a</span> <span class='hs-layout'>(</span><span class='hs-conid'>I</span> <span class='hs-conid'>Nothing</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>a</span>
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