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typo [thanks GG]

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Mark Pilgrim
2010-01-11 17:39:39 -05:00
parent 3a243597e6
commit 9c0f135c74
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generators.html
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@@ -215,7 +215,7 @@ def build_match_and_apply_functions(pattern, search, replace):
<ol>
<li><code>build_match_and_apply_functions()</code> is a function that builds other functions dynamically. It takes <var>pattern</var>, <var>search</var> and <var>replace</var>, then defines a <code>matches_rule()</code> function which calls <code>re.search()</code> with the <var>pattern</var> that was passed to the <code>build_match_and_apply_functions()</code> function, and the <var>word</var> that was passed to the <code>matches_rule()</code> function you&#8217;re building. Whoa.
<li>Building the apply function works the same way. The apply function is a function that takes one parameter, and calls <code>re.sub()</code> with the <var>search</var> and <var>replace</var> parameters that were passed to the <code>build_match_and_apply_functions()</code> function, and the <var>word</var> that was passed to the <code>apply_rule()</code> function you&#8217;re building. This technique of using the values of outside parameters within a dynamic function is called <em>closures</em>. You&#8217;re essentially defining constants within the apply function you&#8217;re building: it takes one parameter (<var>word</var>), but it then acts on that plus two other values (<var>search</var> and <var>replace</var>) which were set when you defined the apply function.
<li>Finally, the <code>build_match_and_apply_functions()</code> function returns a tuple of two values: the two functions you just created. The constants you defined within those functions (<var>pattern</var> within the <code>match_rule()</code> function, and <var>search</var> and <var>replace</var> within the <code>apply_rule()</code> function) stay with those functions, even after you return from <code>build_match_and_apply_functions()</code>. That&#8217;s insanely cool.
<li>Finally, the <code>build_match_and_apply_functions()</code> function returns a tuple of two values: the two functions you just created. The constants you defined within those functions (<var>pattern</var> within the <code>matches_rule()</code> function, and <var>search</var> and <var>replace</var> within the <code>apply_rule()</code> function) stay with those functions, even after you return from <code>build_match_and_apply_functions()</code>. That&#8217;s insanely cool.
</ol>
<p>If this is incredibly confusing (and it should be, this is weird stuff), it may become clearer when you see how to use it.