Parse formulas of the type "f(x)*y"

[maroua97]

Hello, I have discovered the NCalc .NET evaluator and tested it. It meets exactly my criteria. Actually, I need to parse a formula like "x+3-f(x)", x could be numerical or a string (I couldn't find another evaluator than can deal also with string variables), and f is a function that I can define.
However, my company wants a more maintained and sustainable parser, created and managed by a company. Your website (https://archive.codeplex.com/?p=ncalc) reference to jint? Does it also parse formulas with numerical and string arguments, and with user defined functions? If so, how so?