The expressions are to be Boolean expres-sions, and there is a shell of a program for you to expand upon. The symbol table package permits one to store and retrieve values associated with variables. Here you find the tokens that are the internal representations for the lexemes. The only variant that has a field other than type is the Identifier token. The language is a series of statements separated by semi-colons and terminated by a period.
Statements are of two types.
Assignment statements consist of an identifier, followed by an assignment operator, followed by an expression. Display statements begin with an assignment operator, and are followed by an expression. In either case, the expression is evaluated and its truth value is displayed. For assignment statements, the value is also stored in the symbol table. You will be expanding that repertoire.