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[weaver@RUSSIAN.SPA.Symbolics.COM (Eric Weaver)]

    Date: Fri, 14 Sep 90 10:59:53+0900
    From: kddlab!atr-ln.atr.co.jp!myers@uunet.UU.NET (John K. Myers)

    I'm building a rewriting system that takes a structure, looks at its
    name, and calls a special rewriting function for it.  The system has
    to be blazingly fast.  There will be about 1000 kinds of structures.

    The question is how to rapidly associate a name with a rewriting function.
    Three methods come immediately to mind:
    1) Use a CASE on the names, to get to the functions;
    2) Use the name as a key to a hash-table that stores the functions;
    3) Use the name to build a function-name, using (intern (string-append )).
       Then call the function using (apply func-name).

Even faster:


4. Use the name itself, assuming a symbol, as a function name.  Then just
(funcall name)... 

5. Keep the rewriting function in a slot of the structure, if it's not
too big a hassle.  This takes the obvious extra storage.

6. Use a property on the name symbol and do GET on that.

If the names are not symbols, 2 is about the fastest, since 3 uses 2.


Eric C. Weaver
& Assocs. Inc.
Consultant