Auli

Auli is a very (very very) limited Lisp dialect.

How to use Auli

Pre-requisites

This project uses yarn and Node.js. It manages these tools using volta. Install all three and volta should make sure you're using the right versions.

Setup

1. yarn install to install dependencies.
2. yarn tests to ensure everything is working ok.

Evaluating expressions

Auli provides a repl and the ability to evaluate source files.

• To start the repl: yarn auli
• To evaluate a file: yarn auli <path>

Why Auli?

As the name Lisp is derived from "list processor", so the name Auli is derived from "almost useless Lisp interepreter".

Auli is intended as a hobby language to explore the craft of programming languages with. The choice of a Lisp dialect came down to three factors:

1. The straightforward syntax and expression oriented nature of Lisp hopefully simplify the parser implementation, allowing me to roll my own without it becoming too much of a horrorshow.
2. There are powerful language features that can provide stretch goals and new challenges (e.g.: tail-call elimination, macros).
3. Lisps are fun to program in and even relatively limited dialects like MIT Scheme can be used to implement interesting programs.

How good is Auli?

Auli will be assessed once it has a minimum of features required to implement a few canonical programs (draft list below). In the meantime, it is enough to say that Auli is thoroughly flawed and already I have realised a number of mistakes in my approach.

Suggested benchmark programs:

• Hello World
• FizzBuzz
• Fibonacci nth term

Development notes

Extending the standard library

1. Add the new symbol to the appropriate array so it can be recognised by the tokeniser.
2. Add the new operation name to the appropriate enum in types.
3. Add a case for the new symbol to the appropriate getOperationName function in the parser.
4. Use .set() to extend the standard library with an implementation of the new function.
5. Handling of the new function can be tested by adding expected values to the appropriate testOperation arrays in test data.

ToDo

Bugs

• Unable to evaluate multiple nested expressions (e.g.: (if (> 2 3) 6 ((print 'this path') (+ 2 4)))))

Functionality

MVP

• Can define and reference variables
• Can define and reference functions
• Can evaluate mutiple expressions (begin)

StdLib

• concat
• list

Pipe dreams

• Anonymous functions / let
• Tail-call elimination
• Standard library sufficient to complete SICP exercises

Quality

High priority

• Contextual error messages (position at minimum)
• Test eval / entry functions
• Help / manual page
• Automated tests

Low priority

• Stricter types on expression params (types > arrays)
• Pre-commit hooks
• Update terminology to match standards

Project

• Publish to npm
• Compile to bytecode
• Haskell port
• Web based repl / mini ide
• Logo