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ParenSymmetry Lab

Overview

This lab teaches you to implement a balanced parentheses checker, a fundamental algorithm used in programming language processing. You'll learn to determine whether parentheses () in a string are properly balanced - meaning every opening parenthesis has a corresponding closing parenthesis in the correct order.

Why This Matters: Lexing and Parsing

Checking balanced delimiters is a core component of how programming languages are processed by computers. This involves two key steps:

Lexing (Lexical Analysis)

Lexing is the process of breaking source code into meaningful pieces called "tokens." Think of it like breaking a sentence into individual words. A lexer scans through your code character by character and groups them into tokens like keywords (if, while), operators (+, -), identifiers (variable names), and delimiters ((), {}, []).

For example, the code if (x > 5) would be tokenized as:

  • if (keyword)
  • ( (opening delimiter)
  • x (identifier)
  • > (operator)
  • 5 (number)
  • ) (closing delimiter)

Parsing (Syntax Analysis)

Parsing takes the tokens from lexing and builds a structure that represents the program's syntax - like creating a sentence diagram. The parser needs to verify that delimiters are properly balanced to ensure the code structure makes sense.

Consider this code:

if (condition) {
    print("hello")
}

The parser must verify that:

  • The ( after if has a matching )
  • The opening { has a matching }
  • They're nested correctly

Real-World Applications

Balanced delimiter checking is used in:

  • Code editors - highlighting matching brackets as you type
  • Compilers - validating program structure before translation
  • IDEs - providing syntax error detection
  • Mathematical expressions - ensuring formulas are correctly formed

Lab Structure

  • java/ - Java implementation with Maven build system
  • python/ - Python implementation with unittest framework

Both versions include the same core challenge: implement the isBalanced() method to correctly identify balanced parentheses in strings.

Getting Started

Choose your preferred language directory and follow the README instructions to implement and test your solution. Remember: this simple algorithm is the foundation for understanding how programming languages are processed!