monkey-lang

A TypeScript implementation of C-like language based on excellent Writing An Interpreter In Go book.

How To Install

0. Download and install Node
1. Open Terminal
2. $ git clone https://github.com/michalholasek/monkey-lang.git
3. $ npm i && npm run build

How To Run

1. Open Terminal
2. $ cd <monkey-lang directory>
3. $ node ./dist/monkey.js

REPL

Welcome to monkey-lang REPL!
Hit RETURN once to enter multiline editing, twice to enter your command.
> 5
5
> let let = 5;
invalid token(6, 1): expected Identifier, got Let instead
> quit
Exiting monkey-lang REPL...

Features

• C-like syntax
• Integer, boolean, and string primitive data types
• Array and hashtable support
• Variable bindings
• Let and Return statements
• If-Else conditionals
• Basic arithmetic for integer expressions
• First class and higher-order functions, closures
• Built-in utility functions

Types

Type	Examples
int	0, 123, -29
boolean	true, false
string	"Astralis"
array	[], [1, 2, 3], [fn (x) { return x; }, [], ""]
hash	{}, { "key": "value" }, { false: true, 1: "Yes!" }

Variable Bindings

> let five = 5;
> five
5

Integer Arithmetics

> let ten = 5 + 10 - 5;
> let eleven = (5 * 2) + 1;
> ten
10
> eleven
11

Let and Return Statements

> let identity = fn(value) { return value };
> identity(42);
42

Functions

> let add = fn(x) {
    return fn(y) {
      return x + y;
    }
  };
> let addTwo = add(2);
> addTwo(5);
7

If-Else Conditionals

> let elsy = fn(value) {
    if (value) {
      return value;
    } else {
      return "Alternative.";
    }
  };
> elsy(false);
Alternative.

Built-in Functions

> len("abc")
3
> len([1])
1

> push([1], 2, 3)
[1, 2, 3]

> first([1, 2, 3])
1

> last([1, 2, 3])
3

> rest([1, 2, 3])
[2, 3]

> puts(1, 2, 3)
1
2
3
> puts("Hello!")
"Hello!"

License

MIT