Custom Expression Parser in C#

Question

I am working on a calculator program for a finance application. I need to parse and evaluate complex financial expressions like mentioned below.

The expression is a mix of custom functions and arithmetic expressions. I am using NCalc to resolve the Arithmetic expressions. However, I am having trouble in resolving the Custom Functions.

IF((COALESCE(X1,X2)-X3+IF(X4<=0,0,X5))>0, CUSTOM_FUNCTION(X6), X7)

Any suggestion on best approach?

I am currently working on a complex logic Involving Recursive calls and Stack Push/Pop. But it is not working.

Answer 1

This is an old problem that was solved a long time ago. The solution is to use a parser generator, not to write your own parser from scratch. There are many options available, one of the more popular ones being ANTLR.

Using a parser generator like ANTLR you can describe your problem using easy-to-understand EBNF-like production rules. The parser generator will generate the complicated logic it seems you are now trying to write by hand, in the language of your choosing, in your case C#. Probably the grammar of your language is already available in this format or you have used this format to describe the language to your users and in your development team.