Re: newbie question on Bison/Yacc

Martin von Loewis <>
4 Jan 2001 01:00:18 -0500

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newbie question on Bison/Yacc (2000-12-31)
Re: newbie question on Bison/Yacc (Martin von Loewis) (2001-01-04)
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From: Martin von Loewis <>
Newsgroups: comp.compilers
Date: 4 Jan 2001 01:00:18 -0500
Organization: Humboldt University Berlin, Department of Computer Science
References: 00-12-124
Keywords: yacc
Posted-Date: 04 Jan 2001 01:00:18 EST writes:

> I am totally new to yacc/bison and wondering if you could help me with
> the following question: I need to parse an algebraic expression and
> calculate its value at a bunch of different points; what are the ways
> (the fastest way?) to reset the "independent vars" and recalculate the
> expression again?

I recommend to build a "symbol table", which maps variable names to
their assigned values. How efficient that is is not really a matter of
bison; you need a fast way to find an identifier in the symbol table
(e.g. by hashing), and you probably need a fast way to clear part of
the variable names when there scope is left (e.g. by chaining multiple
symbol tables, and then discarding the innermost one).


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