Question

I am writing an application that allows a user to enter a boolean expression. I need the ability to evaluate the entered boolean expression at runtime and am looking for both a parser and a expressoin validator.

Parser
The parser needs to take a boolean expression as a string and return true/false.

Example:

string expression = "(1 == 1) && (1 > 0)";
Parser parser = new Parser();
boolean result = parser.parse(expression);  // Result should be True.

In addition to handling boolean expressions I also need it to handle Math.

expression = "((1 + 1 * 2) == 1)";
result = parser.parse(expression);  // Result should be False.

Validate
So that I can tell the user if there is a problem with the expression being entered I also need a way to validate the syntax.

I am working in C# using the .NET Compact Framework, but if you know of something written in another language that may be helpful.

Thanks for any help you can provide.
Tom

Answer 1

http://www.antlr.org

Antlr grammars can be designed to allow for both parsing and evaluation.

Here’s an example: http://www.antlr.org/wiki/display/ANTLR3/Expression+evaluator