cse332: Project 1
Simple Calculator

Due: Wednesday 29 Sept during your assigned lab session

Description

In this project you are to design and implement a simple calculator that understands standard arithmetic expressions. For example:

  a = 2 * 4
  b = 5 * 4 - 1 + 5
  c = a / b
  c

Assume one expression per line (an expression is terminated by a new line). If it is an assignment expression then add/update the symbol's value to an internal table (i.e. dictionary). If it is not an assignment then print the result to standard out. So the example above should print the value of the variable c to standard output.

Your program should take two optional command line arguments, one to specify a data source file another to request a help message.

  calc [-h] [-f fn]
	-h : print a usage message then exit
	-g fn : open file fn and read expressions until eof is encountered
If no source file is specified then read from standard input (i.e. cin).

See roster.cc for an example of how to read from a file or standard input. <> You are not required to define classes for this project (that will come later) but I do want you to solve this problem using recursion (i.e. recursive descent). Your calculator must evaluate standard algebraic expressions (that is, using infix notation) with operators +, -, *, / and = (assignment). I have assigned percedence and associativity to each operator in the table below. You must also support the use of parenthesis to alter expression evaluation order (i.e. to identify subexpressions). The assignment operators are used to assign a value to variables, where a variable is any continuous string of characters a-z. While I want you to use recursive descent, it is up to you if you first transform the infix notation to prefix or postfix.

Operators	Operator	Category	Precedence	Associativity
symbol, literal	simple tokens	primary	5	n/a
- +	negation, plus	unary	4	right-to-left
* /	multiplicative	binary	3	left-to-right
+ -	additive	binary	2	left-to-right
=	assignment	binary	1	right-to-left

You may use any of the classes/templates from the STL. In particular you should consider using the vector (#include <vector>, see the Roster example code referenced above) and map (#include <map>) types. For example, assuming you represent values with the builtin type double (you should) then you can define an associative map as follows:


  map table;
  table["pi"] = 3.14159;
  table["e"] = 2.71828;
  ...
  // assume token is a string, value is a double
  table[token] = value;

Program behavior

You calculator program must read expressions from either a user designated file or standard input (designated by the object cin). When assignment expressions are encountered you must record the value in an internal symbol table but no output is to be generated. All other expressions must be evaluated and the result written to standard output (the object cout).

What to turn in:

Submit your source code, a README file describing the design (see Report.txt or Report.doc) and test data files. See the grading guidelines ProjectGrading.txt or ProjectGrading.doc.

How to turn in

Use the makefile you created in lab 2. To create the file you will turn in run the command

make mkzip

and verify it creates the file properly. Once you are certain everything is in order then execute

make turnin

When to turn in

You must turnin during your assigned lab session. Why? So we (the TAs and myself) can help you to verify your makefile has worked properly.