Monkey Interpreter

This is an interpreter for a 'Monkey' programming language written in Go
I've created this based on the Thorsten Ball's book on writing interpreters.

in order to use the interpreter, locate and move into the root folder and run:

go run .\main\main.go

Features

C-like syntax

variable bindings

integers and booleans

arithmetic expressions

first-class and higher-order functions

closures

Value binding

let age = 1
let result = 10 * (20 / 2) + age
let found = true

Besides integers and booleans, in Monkey, you can also bind functions to names:

let add = fn(a, b) { return a + b }

Implicit return values are also possible which means we can leave out the return:

let add = fn(a, b) { a + b }

Function calling works as expected:

add(1, 2);

More complex functions can also be written:

let fibonacci = fn(x) {
    if (x == 0) {
        0
    } else {
        if (x == 1) {
            1
        } else {
            fibonacci(x - 1) + fibonacci(x - 2);
        }
    }
};

Higher order functions

Monkey also supports higher order functions. These are functions that take other functions as arguments:

let twice = fn(f, x) {
    return f(f(x));
};
let addTwo = fn(x) {
    return x + 2;
};
twice(addTwo, 2); // => 6

Monkey has first class functions. That means functions in Monkey are just values, like integers or booleans.

Closures

Monkey also supports closures. Closure is a function that references variables from outside its body allowing it to encapsulate state and behaviour within functions:

let newAdder = fn(x) {
    fn(y) { x + y };
};
let addTwo = newAdder(3);
addTwo(2); // => 5