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<h3 class="section">8.3 MOP Optimizations</h3>

<p>Even when nothing is known at compile-time about the call to
<code>slot-value</code>, it is possible to do marginally better than in
<a href="Basic-Implementation.html#ex_003aslot_002dvalue_002dusing_002dclass">Example 8.2</a>.  Each effective slot definition
metaobject can cache its own effective method, and the discriminating
function for <code>slot-value-using-class</code> is set to simply call the
function in its slot definition argument.
</p>
<p>(FIXME: I&rsquo;m pretty sure this is a bad plan in general.  Or rather, it&rsquo;s
probably a good plan, but the effective methods should probably be
computed lazily rather than eagerly.  The default image has 8589
closures implementing this optimization: 3 (<code>slot-value</code>,
<code>set-slot-value</code> and <code>slot-boundp</code>) for each of 2863 effective
slots.)
</p>
<p>(Also note that this optimization depends on not being able to
specialize the <code>new-value</code> argument to <code>(setf
slot-value-using-class)</code>.)
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sbcl-doc 2:1.4.5-1 / usr / share / doc / sbcl / sbcl-internals / MOP-Optimizations.html
