Metaprogramming: Difference between revisions

The code now defines the <code>XADD</code> function and immediately, without doing initialization, jumps to the <code>XADD.END</code> label, bypassing both initialization and the function body. The trick here is that it defines the entry point of the function to be the <code>XADD.INIT</code> label. Now the first time <code>XADD</code> is called, control is transferred to <code>XADD.INIT</code>, the expensive initialization is performed, then the <code>XADD</code> function is *redefined* to point to the <code>XADD</code> label as the entry point. From this point onward all calls to <code>XADD</code> only perform the calculation, not the expensive initialization while the expensive initialization isn't paid at all unless the function is used at least once.

 

 

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