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Yann Esposito (Yogsototh) cd3448b73a Regen after devel-clean
2011-09-27 17:11:40 +02:00

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<a href="/Scratch/en/blog/Higher-order-function-in-zsh/" onclick="setLanguage('en')">in English</a>
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Higher order function in zsh
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<p><img alt="Title image" src="/Scratch/img/blog/Higher-order-function-in-zsh/main.png" /></p>
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<p><span class="sc"><abbr title="Trop long à lire">tlàl</abbr>&nbsp;: </span> des fonctions d&rsquo;ordres supérieurs en zsh.</p>
</div>
<p>Tout d&rsquo;abord, pourquoi c&rsquo;est important d&rsquo;avoir ces fonctions.
Plus je programmais avec zsh plus j&rsquo;essayais d&rsquo;avoir un style fonctionnel.</p>
<p>Le minimum pour pouvoir avoir du code plus lisible c&rsquo;est de posséder les fonctions <code>map</code>, <code>filter</code> et <code>fold</code>.</p>
<p>Voici pourquoi avec une comparaison.
Commençons par un programme qui converti tous les gif en png dans plusieurs répertoires projets contenant tous des répertoires resources.
Avant&nbsp;:</p>
<pre class="twilight">
<span class="Comment"><span class="Comment">#</span> for each directory in projects dir</span>
<span class="Keyword">for</span> toProject <span class="Keyword">in</span> /path/to/projects/*(/N)<span class="Keyword">;</span> <span class="Keyword">do</span>
<span class="Comment"><span class="Comment">#</span> toProject is /path/to/projects/foo</span>
<span class="Comment"><span class="Comment">#</span> project become foo (:t for tail)</span>
project=<span class="Variable"><span class="Variable">${</span>toProject:t<span class="Variable">}</span></span>
<span class="Keyword">for</span> toResource <span class="Keyword">in</span> <span class="Variable"><span class="Variable">$</span>toProject</span>/resources/*.gif(.N)<span class="Keyword">;</span> <span class="Keyword">do</span>
convert <span class="Variable"><span class="Variable">$</span>toResource</span> <span class="Variable"><span class="Variable">${</span>toResource:r<span class="Variable">}</span></span>.png
<span class="Constant">\r</span>m -f <span class="Variable"><span class="Variable">$</span>toResource</span>
<span class="Keyword">done</span>
<span class="Keyword">done</span>
</pre>
<p>Après</p>
<pre class="twilight">
<span class="Entity">gif_to_png</span>() { convert <span class="Variable"><span class="Variable">$</span>1</span> <span class="Variable"><span class="Variable">${</span>1:r<span class="Variable">}</span></span>.png <span class="Keyword">&amp;&amp;</span> <span class="Constant">\r</span>m -f <span class="Variable"><span class="Variable">$</span>1</span> }
<span class="Entity">handle_resources</span>() { map gif_to_png <span class="Variable"><span class="Variable">$</span>1</span>/resources/*.gif(.N) }
map handle_resources /path/to/projects/*(/N)
</pre>
<p>Plus de bloc&nbsp;!
Oui, c&rsquo;est un poil plus difficile à lire pour les non initiés.
Mais c&rsquo;est à la fois plus concis et plus robuste.</p>
<p>Et encore ce code ne possède pas de test.
Recommençons sur le même principe.</p>
<p>Trouver les fichiers des projets qui ne contiennent pas de s dans leur nom qui ont le même nom que leur projet.</p>
<pre class="twilight">
<span class="Keyword">for</span> toProject <span class="Keyword">in</span> Projects/*<span class="Keyword">;</span> <span class="Keyword">do</span>
project=<span class="Variable"><span class="Variable">$</span>toProject</span>:t
<span class="Keyword">if</span> print -- project <span class="Keyword">|</span> grep -v s <span class="Keyword">&gt;</span>/dev/null
<span class="Keyword">then</span>
print <span class="Variable"><span class="Variable">$</span>project</span>
<span class="Keyword">for</span> toResource <span class="Keyword">in</span> <span class="Variable"><span class="Variable">$</span>toProject</span>/*(.N)<span class="Keyword">;</span> <span class="Keyword">do</span>
<span class="Keyword">if</span> print -- <span class="Variable"><span class="Variable">${</span>toResource:t<span class="Variable">}</span></span> <span class="Keyword">|</span> grep <span class="Variable"><span class="Variable">$</span>project</span> <span class="Keyword">&gt;</span>/dev/null<span class="Keyword">;</span> <span class="Keyword">then</span>
print -- <span class="String"><span class="String">&quot;</span>X <span class="StringVariable"><span class="StringVariable">$</span>toResource</span><span class="String">&quot;</span></span>
<span class="Keyword">fi</span>
<span class="Keyword">done</span>
<span class="Keyword">fi</span>
<span class="Keyword">done</span>
</pre>
<p>After =&gt;</p>
<pre class="twilight">
<span class="Entity">contain_no_s</span>() { print <span class="Variable"><span class="Variable">$</span>1</span> <span class="Keyword">|</span> grep -v s }
function verify_file_name {
local project=<span class="Variable"><span class="Variable">$</span>1</span>:t
<span class="Entity">contains_project_name</span>() { print <span class="Variable"><span class="Variable">$</span>1</span>:t <span class="Keyword">|</span> grep <span class="Variable"><span class="Variable">$</span>project</span> }
map <span class="String"><span class="String">&quot;</span>print -- X<span class="String">&quot;</span></span> <span class="String"><span class="String">$(</span>filter contains_project_name <span class="StringVariable"><span class="StringVariable">$</span>1</span>/*<span class="String"><span class="String">(</span>.N<span class="String">)</span></span><span class="String">)</span></span>
}
map show_project_matchin_file <span class="String"><span class="String">$(</span> filter contain_no_s Projects/* <span class="String">)</span></span>
</pre>
<p>Also, the first verstion is a bit easier to read.
But the second one is clearly far superior in architecture.
Why?</p>
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Écrit le : 27/09/2011
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