Basic Esolang Interpreter

This project is an interpreter for a basic esoteric programming language (esolang) written in Python. The interpreter can read and execute code written in this esolang, which supports basic arithmetic operations, variable assignments, control flow statements like if, for, and while loops, and print statements.

Project Directory Structure

Basic Esolang Interpreter
├── main.py                # Main entry point for the interpreter
├── lexer.py               # Handles tokenizing the source code
├── parser.py              # Parses tokens into an Abstract Syntax Tree (AST)
├── interpreter.py         # Executes the code by interpreting the AST
├── utils.py               # Shared utility functions and classes
├── grammar.txt            # Defines the esolang grammar and syntax rules
├── examples
│   ├── fibonacci.txt      # Example program to calculate Fibonacci sequence
└── README.md              # Project documentation

• Supported Constructs:
  • Arithmetic and logical operations (addition, subtraction, multiplication, division, exponentiation, and, or, not).
  • Variable assignments.
  • Control flow statements (if, for, and while loops).
  • Print statements.

Esolang Grammar

The grammar of the esolang is defined in grammar.txt. Here is an overview:

program     : statements
statements  : NEWLINE* (expr NEWLINE*)*
expr        : identifier (EQUALS expr)?
             comp-expr ((AND|OR) comp-expr)*
comp-expr   : NOT comp-expr ? arith-expr ((ISE|NE|LT|GT|LTE|GTE) arit-expr)*
arith-expr  : term ((PLUS|MINUS) term)*
term        : power ((MUL|DIV) power)*
power       : factor (POW factor)*
factor      : INT|FLOAT|(expr)|identifier|if-block|for-block|while-block

if-block    : if expr then statements (else statements)? end
for-block   : for identifier EQUALS expr to expr (step expr)? do statements end
while-block : while expr do statements end

Example: Fibonacci Sequence

The following example program calculates the Fibonacci sequence up to the 10th number:

fib_n_2 = 0
fib_n_1 = 1

for n = 0 to 10 do
    if n == 0 then
        print("Fibonacci number ", n, " is ", 0)
    else
        if n == 1 then
            print("Fibonacci number ", n, " is ", 1)
        else
            fib_n = fib_n_1 + fib_n_2
            fib_n_2 = fib_n_1
            fib_n_1 = fib_n
            print("Fibonacci number ", n, " is ", fib_n)
        end
    end
end

Error Handling

The interpreter includes robust error handling for various stages of code execution:

• Lexer Errors: Identifies invalid tokens in the source code.

  input

  1 + (2*3)@
  

  output

  1 + (2*3)@
           ^^
  
  Syntax Error: Invalid Syntax
  line 1, column 10
  

• Parser Errors: Reports syntax errors.

  input

  if 5 > 2 do print(a) end
  

  output

  if 5 > 2 do print(a) end
           ^^
  
  Syntax Error: Invalid Syntax
  line 1, column 10
  

• Runtime Errors: Handles issues such as division by zero, undefined variables or type errors.

  input

  1 + 'string'
  

  output

  1 + 'string'
    ^^
  
  Runtime Error: Invalid operator '+' for 'INT' and 'STRING'
  line 1, column 3
  

How to Run the Interpreter

To execute the interpreter, use the following command:

  python3 main.py [file]

• REPL Mode: If no file is provided, the interpreter will run in interactive mode, allowing you to enter and execute code interactively.
• Script Mode: If a file is provided, the interpreter will execute the code contained in the file.

Future Enhancements

• Add support for functions and user-defined procedures.
• Implement enhanced debugging features.
• Extend the language with additional built-in functions and data structures.

Happy Coding!!