Question

Converting an old program into an ASP.NET c# site.

I have a table full of functions and a table full of variables with their corresponding values. I’ve written a function to evaluate the answers but need to format the formulas in order to pass the variable in.

For example:

V(totalValue) * V(CoFriction(s)) ==>  V("totalValue") * V("CoFriction(s)")

How can I replace the V(<variable>) to V("<variable>"). Nested parenthesis are possible!

I’ve tried regexp like – V\([^\(\)]+\) only to fail on the nested paren.

Answer 1

You can achive it in .net using a balancing group:

string s = "V(totalValue) * V(CoFriction(s)) * V(a(()b)c()d((())))";

string vPattern =
@"V\(
(       #capturing group, for $1 to work
    (?:
        (?<open>\()|    #push to stack OR
        (?<-open>\))|   #pop from stack OR
        [^()]           #match anything else
    )+?
)
(?(open)(?!))   #assert there are not extra (
\)";

s = Regex.Replace(s, vPattern, "V(\"$1\")", RegexOptions.IgnorePatternWhitespace);

The regex works exactly for the posted scenarios – it will fail miserably if the input isn’t valid, so you assume it is (specifically, when you have extra closing parentheses).