Calculate special expression in C #

Question

I have a string that has special substrings in a special format:

$ (variableName)

And this pattern can be repeated multiple times:

$ (variableName $ (anotherVariableName))

For example: [test line]

Here is a test line containing $ (variableA) and $ (VariableB $ (variableC))

For this test string, suppose that

$ (variableA) = A, $ (variableB) = B, $ (variableC) = C, $ (variableBC) = Y

I want to replace those special patterns -> $ (variableName) with actual values, such as the resulting string should be:

Here is a test line containing A and Y

Any suggestion for a versatile and elegant solution?

Answer 1

Here is a simple solution that performs recursive descent analysis :

public static string Replace( string input , ref int pos , IDictionary<string,string> vars , bool stopOnClose = false ) { var res = new StringBuilder(); while (pos != input.Length) { switch (input[pos]) { case '\\': pos++; if (pos != input.Length) { res.Append(input[pos++]); } break; case ')': if (stopOnClose) { return res.ToString(); } res.Append(')'); pos++; break; case '$': pos++; if (pos != input.Length && input[pos] == '(') { pos++; var name = Replace(input, ref pos, vars, true); string replacement; if (vars.TryGetValue(name, out replacement)) { res.Append(replacement); } else { res.Append("<UNKNOWN:"); res.Append(name); res.Append(">"); } pos++; } else { res.Append('$'); } break; default: res.Append(input[pos++]); break; } } return res.ToString(); } public static void Main() { const string input = "Here is a test string contain $(variableA) and $(variableB$(variableC))"; var vars = new Dictionary<string, string> { {"variableA", "A"}, {"variableB", "B"}, {"variableC", "C"}, {"variableBC", "Y"} }; int pos = 0; Console.WriteLine(Replace(input, ref pos, vars)); } 

This solution reuses the Replace implementation to create the name of the variable you would like to replace by calling yourself with the stopOnClose flag set to true . The top-level call does not stop at reaching the ')' character, allowing you to use it without binding.

Here is a demonstration of ideon.