Re: [Boost-users] Suggestions for Simple Expression Evaluation

From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2008-07-28 19:42:04

AMDG

Richard L. Aurbach wrote:
> I am looking for some code to handle simple expression evaluation -- 
> cases like 
> "a | b | c", or "(a + b)/2", 
> where 'a', 'b', and 'c' are named constants that I can evaluate by 
> lookup. I.e., code to evaluate simple expressions to produce integer 
> results.
>
> I'm looking for something light-weight and easy to use -- something 
> that justifies a decision to look elsewhere rather than writing the 
> 10-million-and-first simple evaluator. (I know that lots of folks have 
> written this type of code as a homework assignment in a data 
> structures course.  As it happens, I don't have an old assignment to 
> look up and am hoping to spare the time doing it now :-) )
>
> I didn't see anything in the boost library that didn't appear to be 
> incredible overkill, but I'm happy to be proven wrong about that.
>
> Anyway, I would be very interested in some suggestions (using boost or 
> otherwise) that can help me implement run-time evaluation of simple 
> expressions without a major investment in the size or complexity of my 
> application.

Take a look at Spirit.  This example is similar to what you are trying 
to achieve.
http://www.boost.org/doc/libs/1_35_0/libs/spirit/example/fundamental/phoenix_calc.cpp

You can use Spirit's symbol table class:
http://www.boost.org/doc/libs/1_35_0/libs/spirit/doc/symbols.html

In Christ,
Steven Watanabe