Re: what scanner scheme is efficient?

lloix@star.spb.ru <lloix@star.spb.ru> wrote:
>Thus the question is simple, how do professionals design their scanners
>and tables, what do they do with keywords, and what is the more effective
>approach?


The best approch is to have an rule for 'IDENT' in the lexical
scanner and an stage IDENT->RESERVED_WORD after the call to the
scanner. This has a few advantages:


  1. You can modify the resword-table (example: ansi in C-grammar )


  2. You can have context-sensitive resword-scope. (example the Grammar
        says what words are useful (like 'type-name','undefined ident' in pascal)


The resword table is an simple hash (O(1) like the scanner - so
you have O(1) + O(1) = O(1)) and can have hash-keys with or without
case-sensitivity.


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Peter Brueckner, Brueckner&Jarosch Ing.-GmbH Erfurt, Germany 99084 Erfurt
Andreasstr. 37, TEL +49=361-64318.11, FAX .12, EMail peter@bj-ig.de,-42-


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