Python Lexer and Parser with PLY

Overview

This project includes a lexer and parser implementation using the PLY (Python Lex-Yacc) library. The lexer and parser are designed to handle a custom syntax, which supports basic control structures and functions, including for loops, while loops, if-else conditions, and function definitions. The grammar also supports list and tuple declarations.

Features

• Lexer: Tokenizes input based on predefined patterns, including keywords (for, while, if, else, elif, def), delimiters (:, ,, (, ), {, }, [, ], "), and indentation-based changes.
• Parser: Parses the tokenized input to build a syntactic structure. Supports:
  • For loops
  • While loops
  • If-else conditions
  • Function definitions
  • List and tuple declarations

Requirements

• Python 3.x
• PLY library

Installation

Install PLY using pip if it's not already installed:

pip install ply

Usage

• Define the Syntax: The lexer and parser are defined to handle a custom syntax.
• Input the Code: Run the script and input the code lines interactively. End input with a blank line.
• Parse and Validate: The parser checks the input syntax and prints validation messages for the different types of constructs.

Enter the syntax
for i in range(10):
    print(i)

def my_function(x, y):
    return x + y

if x > 5:
    print("x is greater than 5")
else:
    print("x is 5 or less")

while x < 10:
    x = x + 1

The above input will produce output indicating the validity of function definitions, loops, and conditionals.

Lexer Rules

• Keywords: for, while, if, else, elif, def, in, range
• Identifiers: Variable and function names
• Delimiters: :, ,, (, ), {, }, [, ], "
• Indentation: Managed using a stack to handle nested blocks

Parser Rules

• For Loop: for IDENTIFIER in cond : INDENT statements DEDENT
• Function Definition: def IDENTIFIER ( args ) : INDENT statements DEDENT
• If-Else Condition: if cond : INDENT statements DEDENT (elif or else ...)
• While Loop: while cond : INDENT statements DEDENT
• Tuple Declaration: ( tupl_elements )

Error Handling

Errors are reported with line and position details if syntax issues are detected.

#Contributing Contributions are welcome! Please open an issue or submit a pull request to contribute to the project.