FLIP — Flo's LISP

This is just for fun. The code is opensource, because I was looking for similar projects before I started and couldn't find many. So feel free to inspire yourself if you want to write your own programming language or whatever.

I initially followed this marvelous guide: Scheme from Scratch.

Afterwards I've taken the liberty of diverging from the official scheme spec wherever I felt like it. I didn't implement automatic tail-call-optimization for example. Instead I did it the clojure way (:copyright:) with recur.

I'd love to receive feedback on the code, so if you want to chat about it, ask a question or propose an improvement feel free to open an issue on GitHub!

###Documentation Can be found in the docs folder of the repo.

###Screenshots

###Features In no particular order and incomplete:

• REPL with history and autocomplete

• Primitive types:

  • Bool (true & false, not #t & #f)
  • Char
  • Integer (i64, no floats)
  • List
  • String (UTF8)
  • Symbol (ASCII, interned strings)

• All types are immutable, you can only change bindings

• Parsing with good error messages (inspired by rustc)

• Evaluate S-expressions

• Define items in current scope with (define *name* *whatever*)

• Define rust fns and make them callable in flip (see src/native for examples)

  • I implemented some stuff, like basic math, list operations, etc. all in src/native/primitive_forms.rs with a ton of macros to reduce boilerplate
  • Type conversions also in src/native/primitive_forms.rs

• Create procedures with (lambda *optional_name* (args*) code)

  • They have their own scope

• GC: No, just Rc for all values

• Dynamic scopes

  • (let (x 1 y 2 z (+ x y)) (list x y z)) gives you (1 2 3)
  • let behaves like let* in clojure
  • there's also loop, which works like let, but establishes a recursion point, see clojure docs

• Tail calls

  • (recur arg1 arg2 ..) will make a tail call
  • works the same as in clojure
  • recur should only be used in tail position
  • when recur is evaluated, code execution jumps to the next recursion point
  • lambda and loop both create a recursion point
  • example: (loop (x 1) (if (< x 10) (recur (+ x 1)) x )) this is a tail-call-optimized loop that counts from 1 to 10

###Planned Features

• Conditions
• Refactor Value so that it doesn't use Rc for everything, just Strings and Lists maybe
• Float support
• Maybe a better tokenizer with nom
• Concurrency
• stdlib