generic expression evaluation

[Karthikeyan Ramnath]

Hello,
I am pretty new to Lex and Yacc, two days to be precise. 
Earlier I was faced with the problem of evaluating a logical 
expression, like
((A < 10) & (A > 2)) & (NOT(B==3))
I had implemented a rather simple parser and used a tree to 
evaluate this expression. But now the thing is that the fields, 
A,B,C etc.. are configurable, as is the entire expression. Each 
field is an object in C++ with specific datatype binding.
Faced with this problem, I was told to look into Lex and Yacc 
for implementing a generic solution. But my lack of expertise 
is posing a serious problem.
Could you kindly help me out? What do i read up? Where can i 
find more useful information to get the job done quickly?
Thanks a lot.
Karthikeyan.R
 
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