title: Exprtk evaluating and returning string expressions
body: <p>I'm evaluating using exprtk to evaluate string expressions (e.g., "a"+"b") an, as such, I've tried to create a std::string parser (exprtk::parser).</p>
  
  <p>This throws out a bunch of errors in compilation about multiple overloaded methods that instantiate to the same signature (parser::operator() and parser::get_variable()).</p>
  
  <p>I haven't found anything in the documentation to do this although it says it handles string types.</p>
  
  <p>How would I be able to do this?</p>