The second project involves completing and extending the C++ program that evaluates statements of an expression language contained in the module 3 case study.
The statements of that expression language consist of an arithmetic expression followed by a list of
assignments. Assignments are separated from the expression and each other by commas. A semicolon
terminates the expression. The arithmetic expressions are fully parenthesized infix expressions
containing integer literals and variables. The valid arithmetic operators are +, –, *, /. Tokens can be
separated by any number of spaces. Variable names begin with an alphabetic character, followed by any
number of alphanumeric characters. Variable names are case sensitive. This syntax is described by BNF
and regular expressions in the case study.
The program reads in the arithmetic expression and encodes the expression as a binary tree. After the
expression has been read in, the variable assignments are read in and the variables and their values of
the variables are placed into the symbol table. Finally the expression is evaluated recursively.
Your first task is to complete the program provided by providing the three missing
classes, Minus, Times and Divide.
Next, you should extend the program so that it supports relational, logical and conditional expression
operators as defined by the following extension to the grammar:
Note that there are a few differences in the use of these operators compared to their customary use in
the C family of languages. Their differences are:
In the conditional expression operator, the symbols are reversed and the third operand represents the condition. The first operand is the value when true and the second the value when false
The logical operators use single symbols not double, for example the and operator is & not &&
The negation operator ! is a postfix operator, not a prefix one
There are only three relational operators not the usual six and the operator for equality
is = not ==