Interpreter for the Monkey programming language

Based on Thorsten Ball's Writing an Interpreter in Go book.

Syntax

let a = 2 + 3 * 2; // Arithmetic expressions are supported
let b = "Hello"!; // Strings work too
let c = true; // And booleans

// Hashmaps and arrays are supported as well
let hashmap = {
    "yes": true,
    "no": false
}
hashmap["maybe"] = "?"; // Assign values to keys
let x = hashmap["maybe"] + " " + b; // And access them

let y = [1, 2, true];
puts(y[1]); // 2



puts(x); // You can also print values!

// Conditionals, implicit and explicit returns are supported
// as well
let fibonacci = fn(x) {
    if (x == 0) {
        0
    } else {
        if (x == 1) {
            return 1;
        } else {
            fibonacci(x - 1) + fibonacci(x-2);
        }
    }
}

// We can also create closures!
let newGreeter = fn(greeting) {
    fn(name) {greeting + " " + name + "!"};
};

let hello = newGreeter("Hello");
puts(hello("world")); // Hello world!

Builtins

The interpreter provides a few builtin functions to interact with its objects:

• len(String | Array)
• first(Array)
• last(Array)
• rest(Array)
• push(Array, Any)
• puts(Any) (Each object provides its string implementation)

Usage

• To run the repl:

go run main.go

• To pass a file to the interpreter:

go run main.go [file_path]

Examples

Check out the examples folder to see how monkey functions in practice:)