HW 3 Problem 2 Solution

Description

Question: Write a simple parser for the following EBNF grammar:

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Provided test cases:

1. Input: “bc”

Print: “Input is valid”

2. Input: “acd”

Print: “Syntax error at character position 2”

3. Input: “aaad”

Print: “Input is valid”

4. Input: “c”

Print: “Input is valid”

5. Input: “2yz”

Print: “Syntax error at character position 0”

6. Input: “” (empty)

Print: “Syntax error at character position 0”

Note: First language is Python

Algorithm/Pseudo code:

Actual Code:

Syntax Error:

• When I raise an exception, I need to convert self.char_pos to a string when I create the error message

Working Code

Debugging

1. Did not increment char_pos before calling self.fun_x() in line 12. To fix:

2. Did not account for the fact that we can have multiple “A”s in a row. Added a while loop to account for multiple “A”s

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3. Need to catch error involving multiple repeating “b”s

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Extra Test Cases Used for Debugging:

1. Input: “abd”

Print: “Syntax error at character position 1”

2. Input: “b”

Print: “Syntax error at character position 0”

3. Input: “aaaa”

Print: “Syntax error at character position 3”

4. Input “bbbb”

Print: “Syntax error at character position 1”

5. Input: “cc”

Print: “Syntax error at character position 1”

6. Input: “3”

Print: “Syntax error at character position 0”

Note: Second language is Rust

Actual Code:

Syntax Error:

1. Whenever I am indexing the input string, I need to convert self.char_pos to usize using self.char_pos as usize

Working Code

Debugging

1. Threw errors using custom error, but I never caught the error. To fix, I need to add a match statement at the end of fun_s()

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