64 lines
2.8 KiB
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64 lines
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<a name="MOP-Optimizations"></a>
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Previous: <a rel="previous" accesskey="p" href="Compiler-Transformations.html#Compiler-Transformations">Compiler Transformations</a>,
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Up: <a rel="up" accesskey="u" href="Slot_002dValue.html#Slot_002dValue">Slot-Value</a>
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<h3 class="section">7.3 MOP Optimizations</h3>
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<p>Even when nothing is known at compile-time about the call to
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<code>slot-value</code>, it is possible to do marginally better than in
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<a href="ex_003aslot_002dvalue_002dusing_002dclass.html#ex_003aslot_002dvalue_002dusing_002dclass">Example 7.2</a>. Each effective slot definition
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metaobject can cache its own effective method, and the discriminating
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function for <code>slot-value-using-class</code> is set to simply call the
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function in its slot definition argument.
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<p>(FIXME: I'm pretty sure this is a bad plan in general. Or rather, it's
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probably a good plan, but the effective methods should probably be
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computed lazily rather than eagerly. The default image has 8589
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closures implementing this optimization: 3 (<code>slot-value</code>,
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<code>set-slot-value</code> and <code>slot-boundp</code>) for each of 2863 effective
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slots.)
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<p>(Also note that this optimization depends on not being able to
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specialize the <code>new-value</code> argument to <code>(setf
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slot-value-using-class)</code>.)
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