nouhi / diy-lisp Goto Github PK

batteries included, some assembly required

In this tutorial/workshop we'll be implementing our own little language, more or less from scratch.

By the end of the tutorial you will be the proud author of a programming language, and will hopefully better understand how programming languages work on a fundamental level.

We will make a relatively simple, but neat language. We aim for the following features:

• A handful of datatypes (integers, booleans and symbols)
• Variables
• First class functions with lexical scoping
• That nice homemade quality feeling

We will not have:

• A proper type system
• Error handling
• Good performance
• And much, much more

The language should be able to interpret the following code by the time we are done:

(define fact 
    ;; Factorial function
    (lambda (n) 
        (if (eq n 0) 
            1 ; Factorial of 0 is 1
            (* n (fact (- n 1))))))

;; When parsing the file, the last statement is returned
(fact 5)

The syntax is that of the languages in the Lisp family. If you find the example unfamiliar, you might want to have a look at a more detailed description of the language.

Before we get started, make sure you have installed Python and Pip.

Then install nose, the Python test framework we'll be using.

pip install nose

Optional: If your are familiar with virtualenv you might want to do this in a separate pyenv.

Finally, clone this repo, and you're ready to go!

git clone https://github.com/kvalle/diy-lisp.git

Also, if you're unfamiliar with Python, you might want to have a look at the basics in the Python tutorial before we get going. There is also the small Python cheat sheet to help you along.

The workshop is split up into seven parts. Each consist of an introduction, and a bunch of unit tests which it is your task to make run. When all the tests run, you'll have implemented that part of the language.

Have fun!

• Part 1: parsing
• Part 2: evaluating simple expressions
• Part 3: evaluating complex expressions
• Part 4: working with variables
• Part 5: functions
• Part 6: working with lists
• Part 7: using your language