Interpreter of ABr language

This project is an interpreter for a programming language that I created: the ABr language

ABR = Arthur Bricq

A programming language parser and its interpreter that I made to learn more about parsing, programming language theory and how interpreters work.

Features of the language

The language is a sort of mix between C-syntax (with the concept of expressions and statements) that is very similar to Python (variables are typed only at runtime)

The features of languages are the following.

• C-like differentiation of expressions and statements
• Python-like typed variables: a = 1
  • Currently supported types: bool, int, list, string
• Python-like functions: fn foo(first_arg, second_arg)
  • Like in python, variables are typed but the type is not declared. Furthermore, it is possible to change the type of variables.
• Python-like list: my_list = [1,2,3]
  • access: my_list[0]
  • mutation: new_list = my_list + [4]
• If, Else-If, Else: if (false) {foo()} else {bar()}
• Comments after //
• A standard-library with basic functions:
  • print(a,b,c) to print many variables
  • len(my_list) to get the length of a list
• All common math operation supported and can be used in a shell.

Furthermore, the parser and interpreter comes with a full supports for error. Here's an example of this.

I surely agree that the syntax of this language is weird. This is mostly because I had no clear vision of what I would do, when I would stop, and what would be more difficult. Really, this is a learning project.

Examples

Hello world

fn hello_world() {
  print("Hello world!");
}

fn main() {
  // A small example that illustrates how to print `Hello world` on the screen
  hello_world();
  return 0;
}

Fibonacci with recursive function

The famous Fibonacci example, with a recursive call.

fn fib(n) {
  if (n == 0) {return 0;}
  if (n == 1) {return 1;}
  return fib(n - 1) + fib(n - 2);
}

Fibonacci with a loop

Same example, but to print the first n-values in order

/// A function that prints the n first values of the Fibonacci sequence.
/// Note that this function does not use recursive function but instead illustrates
/// how to use a loop.
fn print_fib_until(n) {
    first = 0;
    second = 1;
    next = first + second;
    
    if (n <= 0) { return -1; }
    print(first); 
    
    // print the first values
    if (n >= 1) { print(second); }
    if (n >= 2) { print(next); }
    
    // check that there is a loop needed
    if (n < 3) { return 0; }
    
    n = n - 2;
    loop {
        first = second;
        second = next;
        next = first + second;
        n = n - 1;
        print(next);
        if (n == 0) { break; }
    }
    
    return 0;
}

Shell-like interpreter

By running cargo run, you can immediately start using the interpreter

Missing features

These features are missing for ABr to be 'ready'

• More operator: ||, &&
• Char