Would really appreciate some assistance.

In this assignment we're going to extend the arithmetic expression tree presented in class to handle function calls, with a single parameter. The grammar presented in class was simply exp -NUM expVAR exp-> ' (' exp ')' expexp expexp 0P exp To extend this to functions, we add an additional rule exp -FNAME exp')' The rules for function names are similar to those for variables, except that underscore - characters are allowed in function names but not in variable names. You should implement the functions vector::iterator start, vector string>::iterator finish, int& prec); In this assignment we're going to extend the arithmetic expression tree presented in class to handle function calls, with a single parameter. The grammar presented in class was simply exp -NUM expVAR exp-> ' (' exp ')' expexp expexp 0P exp To extend this to functions, we add an additional rule exp -FNAME exp')' The rules for function names are similar to those for variables, except that underscore - characters are allowed in function names but not in variable names. You should implement the functions vector::iterator start, vector string>::iterator finish, int& prec)