1. Assignment #3 Programming Language, Spring 2003
Calculator
Assignment #3
Programming Language, Spring 2003

2. Specification (1) Calculator Application. Only integer arithmetic
The operations are addition, subtraction and multiplication
Use an arbitrary number of variables whose names are A,B,C,D,E.
Main way of doing calculations
To type in a few formulas and to assign them to variables
Some formulas are complicated expressions, which can refer to yet undefined variables, while other formulas consist of a single number
Then asks for the value of some variables
Redefine some variables and then to reevaluate formulas that depend on these variables

3. Specification (2) Arithmetic Assignment Print Reset var := expression
PRINT var
Reset
RESET

4. Assignment Objectives Implement calculator
Input a few formulas and etc.
Then answer the value of some variables asked for
For each ``PRINT'' statement found in the input file
Output a line containing the numerical value of the specified variable
Or the word ``UNDEF'' if the variable is undefined

5. Input Convention Input file Contain a few formulas and etc. Example
A := B + C
B := 3
C := 5
PRINT D
PRINT A
B := 8
RESET
A := 1 + ( 2 + ( 3 + ( * 6 ) * 7 ) * 8 )
PRINT B

6. Output Convention Output file
For each ``PRINT'' statement found in the input file
Output a line containing the numerical value of the specified variable
Or the word ``UNDEF'' if the variable is undefined
Example
UNDEF 8 13

7. Source Code calculator.scm Output value of the specified variable
Input formulas and etc.
calculator.in
Output value of the specified variable
calculator.out

8. Spec.
Assignment Spec.
System
Unix
Language
Scheme (MIT Scheme)