Documentation

MonkeyScript Web CLI

This is an implementation of the MonkeyScript programming language from the book Writing an Interpreter in GO by Thorsten Ball. I thought it would be cool to turn the REPL project from the book into a Web CLI so anyone can try out MonkeyScript from anywhere!

MonkeyScript is an interpreted programming language implemented in GO. It is JavaScript-like in flavor but much, much simpler and nowhere near as feature rich (however it is still surprisingly capable).

This (Web REPL???) creates a new session in the backend, which is stored as a map[string]object.environment where the string is a session ID that is generated by the backend and saved in the client's session storage (read the book (and look at the code) to learn more). This effectively means that every user gets their own REPL environment that persists for the lifetime of the session.

In the future I may add the ability to "resume" a session with a given session ID as well as store session data in a database. But for now, your code is stored in memory and is wiped when the program restarts.

Supported Data Types

• Integers
• Booleans
• Strings
• Arrays
• Hashmaps
• Functions

Language Features

• Arithmetic Operators
• Boolean Operators
• String Concatenation
• Functions
• Anonymous Functions
• Variables
• Functions as Variables
• Closures
• Many Type Arrays
• Builtins

IMPORTANT!

When you input and submit an equation such as let f = 2 * 2; the REPL will return a blank line, that means it worked!

Any erorrs will be displayed in the REPL output, should they occur.

Examples

Comments: // do NOT work in MonkeyScript. Be sure not to copy the Comments: // if you are trying these examples out! :)

• Print Out

                        puts("Welcome to Monkey!");
                        puts(meaning_of_life());
                        puts(2 + 2);
                    

• Variables

                        let a = "Hello, World!";
                        let b = 1;

• Strings

                        let hello = "Hello";
                        let world = "World";
                        let saying = hello + ", " + world + "!";

• Arrays

                        let a = [1, 2, 3, 4];
                        let b = push(a, 5);
                        b   // [1, 2, 3, 4, 5]
                        
                        // Available builtins
                        len(a)
                        first(a)
                        last(a)
                        rest(a)
                        push(a, 5)

• Hashmaps

                        let people = [{"name": "Alice", "age": 24}, {"name": "Anna", "age": 28}];
                        people[0]["name"];   // Alice

• Functions and Closures

                        let getName = fn(person) { person["name"]; };
                        getName(people[0]);   // Alice
                        
                        let makeGreeter = fn(greeting) { fn(name) { greeting + " " + name + "!" } };
                        let heythere = makeGreeter("Hey there");
                        heythere("Monkey");   // Hey there Monkey!
                    
                        let f = fn(x) {
                            let result = x + 10;
                            return result;
                            return 10;
                         };
                         f(10);

Many more tests are included in the source code! Feel free to take a look 👀

Credits

Project based on Writing an Interpreter in GO by Thorsten Ball

Made with GO & HTMX

Thank You ❤️

- Derek Dorr