Monkey Interpreter 🐵

Tree walking interpreter written in OCaml for Monkey Language - A simple language with C-like syntax.

Implemented by following the book Writing an Interpreter in Go by Thorsten Ball

Features

• Integers, booleans, strings, arrays, hash maps
• A REPL
• Arithmetic expressions
• Let statements
• First-class and higher-order functions
• Built-in functions
• Recursion
• Single line comments

REPL

Requirements

• OCaml
• opam
• dune

Run

dune exec bin/main.exe

Code Examples

Map function

let map = fn(arr, f) {
    let iter = fn(arr, accumulated) {
        if (len(arr) == 0) {
            accumulated
        } else {
            iter(rest(arr), push(accumulated, f(first(arr))));
        }
    };
    iter(arr, []);
};

let arr = [1, 2, 3, 4];
let double = fn(x) { x * 2 };
map(arr, double);

# Output
[2, 4, 6, 8]

Reduce function

let reduce = fn(arr, initial, f) {
    let iter = fn(arr, result) {
        if (len(arr) == 0) {
            result
        } else {
            iter(rest(arr), f(result, first(arr)));
        }
    };
    iter(arr, initial);
};

# Can be used for making sum function
let sum = fn(arr) {
    reduce(arr, 0, fn(initial, el) { initial + el });
};

sum([1, 2, 3, 4, 5]);

# Output
15

TODO

• Errors like in the book
• Tests?
• Closures
• Read from a file

Resources Used

• https://interpreterbook.com
• https://ocaml.org/docs
• https://youtu.be/dycsRSOQjho?si=34wkCgtWgknZNQT5
• https://github.com/ryo-imai-bit/Writing-An-Interpreter-In-Go-In-OCaml