Project 3: Infix-to-Postfix Conversion

COMS 228, 
Project 3: Infix-to-Postfix Conversion

1. Problem Description
Create a program that reads a file input.txt of infix expressions and converts them to the
corresponding postfix version, printing the expressions out to a file output.txt. Please
consult the files 24.pdf and 24 infix2postfix.pptx from the Modules page for details on
the algorithm.
2. Implementation Details
The class containing the main() method should be named Infix2Postfix. The input file is
named input.txt and will contain infix expressions on separate lines. The file will be located
in the default directory of the project. There is no need to implement file choosing functionality.
The output file should be named output.txt and should be created in the same directory as
the input file. Each line of the output file should contain the postfix version of the
corresponding line in the input file.
The infix-to-postfix conversion functionality should correctly account for Parentheses Exponent
Multiplication Modulus Division Addition Subtraction precedence rules. The input file will not
contain braces or brackets BUT may contain many nested levels of parentheses, such as:
12 + ( ( 23 * ( 4 ^ ( 3 – ( 7 / ( 11 ^ 2 ) ) ) ) ) % 25 )
3. Input File Format
The input file is named input.txt and will contain infix expressions on separate lines. The
file will be located in the default directory of the project.
Each line in the file will contain integers, operators, and parentheses. There is no need to guard
against other types of tokens. The expression tokens will be separated by a single space.
Separate infix expressions will be located on separate lines. There may be many infix
expressions in the input file.
Example input file:
12 + ( ( 23 * ( 4 ^ ( 3 – ( 7 / ( 11 ^ 2 ) ) ) ) ) % 25 )
7 ^ ^ 3 ^ ( 4 * ( -15 - -2 ) ) / ( ( 29 + 7 ) ^ 2 )
-4 - ) ) + 15
2 * 3 / 12 - -16
4. Output File Format
The output file should be named output.txt and should be created in the same directory as
the input file. Each line of the output file should contain the postfix version of the
corresponding line in the input file.
Postfix expression operators and operands should be separated by a single space, and postfix
expressions should be printed on separate lines in the file. There should not be any spaces after
the last token on an output line.
If the infix expression contains errors, the first error in the expression should be printed on its
output line INSTEAD of any tokens from the postfix expression. The offending token should be
printed after the error, surrounded by parentheses. If the error token is a parenthesis, it should
not be printed together with the error message:
Error: too many operands (-14)
Error: too many operators (*)
Error: no closing parenthesis detected
Error: no opening parenthesis detected
Example output file:
-5 -2 8 * +
Error: too many operators (^)
Error: no opening parenthesis detected
Error: too many operands (291)
3 4 2 5 ^ - * 6 +
5. Plagiarism
Submitting code that is not your original effort or showing your code to other students is not
permitted.
6. Submission
Write your classes in the edu.iastate.cs228.hw3 package. Turn in the zip file and not
your class files. Please follow the guideline in submission_guide.pdf.
You are not required to submit any JUnit test cases. Nevertheless, you are encouraged to
write JUnit tests for your code. Since these tests will not be submitted, feel free to share them
with other students.
Include the Javadoc tag @author in every class source file you have made changes to. Your
zip file should be named Firstname_Lastname_HW3.zip.