Software Development

1. [15 marks] This question asks you to write a calculator for linear polynomials with integer coefficients.

A linear polynomial is a polynomial of degree 1. Some examples are 32x 5, x + 19, and 75x. For this question, we also consider constants, i.e., polynomials with degree 0, to be a special case of linear polynomials (they are however not in mathematics). For example, we consider polynomials such as 5 as a special case for linear polynomial.

The operations we support include the addition, subtraction and multiplication of two linear polynomials with integer coefficients. These polynomials are all polynomials in variable x.

The syntax of the language of the input for this calculator is:

option left1 left2 right1 right2 There are four and only four space characters in the syntax shown above. Here option,

left1, left2, right1 and right2 are all integers.

The value of option can only be one of the following three integers: 1, 2 and 3, which correspond to addition, subtraction and multiplication, respectively. The left and right operands are left1 x + left2 and right1 x + right2, respectively.

For example, the input 2 4 7 5 15 means (4x + 7) (5x + 15).

The result of the operation on two linear polynomials can be a polynomial of degrees 2 (in the case of multiplication), 1, or 0. Thus your program will consider the result as a polynomial of degree 2, and print the coefficients from the term of the highest degree to the term of lowest degree. More precisely, the output is always of the following form:

result1 result2 result3 

There is one single space between two consecutive values in the output. There is no space at the end of the line, but there is a trailing newline.

The above output means that the result is result1 x2 + result2 x + result3. If the result is a linear polynomial, then result1 is 0. If the result is a constant, then both result1 and result2 are zeroes. Your program is required to print all three values even if they are zeroes.

General Requirements: Use a4q1.c as the name of your C source code file. We will use the following command on bluenose to compile your program:

gcc -o poly a4q1.c 

Your program should NOT print anything to prompt for user input. It accepts user input that meets the syntax specified above.

Therefore, when you run your program by entering ./poly, the program will wait for your input. If you enter 2 4 7 5 15, the program will output 0 -1 -8

Error Handling: Your program should print an appropriate error message and terminate if the user inputs a value for option that is not 1, 2, or 3.

Testing: To test your program automatically, we will use it as a UNIX filter. For the example above, we will test it using the following command in the directory

containing the executable program: 2

echo "2 4 7 5 15" | ./poly 

The output should be:

0 -1 -8

To help you make sure that the output format of your program is exactly what this questions asks for, several files are provided in the following folder on bluenose to show how exactly your program will be automatically tested:

/users/faculty/prof2132/public/a4test/ 

In this folder, open the file a4q1test to see the commands used to test the program with two test cases. The output files, generated using output redirection, are also given.

To check whether the output of your program on any test case is correct, redirect your output into a file, and use the UNIX utility diff (learned in Lab 3) to compare your output file with the output files in the above folder, to see whether they are identical.

Since these output files are given, we will apply a penalty to any program that does not strictly meet the requirement on output format. This includes the case in which your output has extra spaces, or has a missing newline at the end.

We will use different test cases to test your program thoroughly. Therefore, construct a number of test cases to test your program thoroughly before submitting it.

Examples: The following are some examples on running the executable file:

mhe@bluenose:~/csci2132/a4$ echo "1 5 11 2 0" | ./poly 0 7 11 mhe@bluenose:~/csci2132/a4$ echo "1 0 11 2 0" | ./poly 0 2 11 

mhe@bluenose:~/csci2132/a4$ echo "2 0 11 2 0" | ./poly 0 -2 11 mhe@bluenose:~/csci2132/a4$ echo "3 10 11 2 20" | ./poly 20 222 220 

mhe@bluenose:~/csci2132/a4$ echo "5 1 2 5 4" | ./poly Invalid operation.