RustLisp

This is a simple Lisp interpreter written in Rust. It is based on the famous article by Peter Norvig called (How to Write a (Lisp) Interpreter (in Python)). It contains modules that cover lexing, parsing, and evaluating using. You can use RustLisp in an interactive mode (REPL) or by passing a lisp file as an argument! See programs folder for some examples.

Language Overview

• Define variables via the syntax (let my-var <Expr>).
• Define functions via the syntax (fn my-fun (arg1 arg2 arg3) <Expr>) where the final <Expr> the function body.
• If expressions of the form (if (<Expr>) (<Expr>) (<Expr>)) where the first <Expr> is the if-predicate, the second <Expr> is the then-body, and the final <Expr> is the else-body.
• Arithmetic operations +, -, *, /.
• Boolean operations or, and, not.
• Equality comparison operators =, !=.
• Print function that prints a pretty-formatted output of its input.

Example Programs

• Program 1
  • Input

  (
      (let x 1)
      (let y (+ 1 (* 1 1)))
      (fn addOne (x) (+ x 1))
      (let z (addOne y))
      (print x)
      (print y)
      (print z)
  )
  

  • Output

  1
  2
  3
  

• Program 2
  • Input

  (
      (fn addNumbers (x y) (+ x y))
      (let x 1)
      (let y 2)
      (if (= (addNumbers x y) 3)
          (print Success)
          (print Failure)
      )
  )
  

  • Output

  Success
  

• Program 3
  • Input

  (
      (let x True)
      (if (x)
          (print Success-1)
          (print Failure-2)
      )
      (if (not False)
          (print Success-2)
          (print Failure-2)
      )
      (if (or False False (not False))
          (print Success-3)
          (print Failure-3)
      )
      (if (and True True (not True))
          (print Failure-4)
          (print Success-4)
      )
  )
  

  • Output

  Success-1
  Success-2
  Success-3
  Success-4
  

Usage

• To build the program, use the command cargo build
• To run the program, use the command cargo run
• To test the program, use the command cargo test
• To clean the program, use the command cargo clean