Parser Routine in C#

[David]

I need to write a small routine in C# that will parse/decode/evaluate
a complex if statement that will be entered by a user.

, ex. "a= 1 and b = 2 and ((c = 3 and d = 4) or (e = 1 and f = 3))

I know that this is compiler 101, but I have not done this is 20 years
and need some points on how to proceed. I remember using a tree.

Code examples in VB, C++, etc. would be great. All I need is a
direction and I go from there.

Thanks

 

[Alexei Cioina]

Hi David,

I suggest you to use third party tools because you need more than one
year for building own good parser.
Try Cioina.dll from pkCioinaEval package
http://www.geocities.com/alexei_cioina/cioinaeval.html

Cioina.dll equivalent of your expression is:
And(Eq(a,1), Eq(b, 2) ,Or(And(Eq(c, 3),Eq(d ,4)),And(Eq(e, 1),Eq(f ,
3))))

 

[Fred Mellender]

Some source code: http://codeproject.com/csharp/string_evaluator.asp
A parser generator: http://www.nongnu.org/grammatica/

You should also do a Web query on "top down parser" or "recursive descent
parser". This type of parser is pretty easy to write and the articles
should get you started.