# sapling

## Introduction

sapling is a "micro-language" that I'm working on to investigate [Tree Calculus](https://github.com/barry-jay-personal/typed_tree_calculus/blob/main/typed_program_analysis.pdf) .

It offers a minimal amount of syntax sugar:

- `t` operator behaving by the rules of Tree Calculus
- Function ("variable") definitions
- Lambda abstractions
- List, Number, and String literals (WIP)

This is an active experimentation project by [someone who has no idea what they're doing](https://eversole.co).

## What does it look like?

```
false      = t
_          = t
true       = t t
id         = (\a : a)
triage     = (\a b c : t (t a b) c) 
match_bool = (\ot of : triage of (\_ : ot) t)
and        = match_bool id (\_ : false)
if         = (\cond then else : t (t else (t t then)) t cond)
triage     = (\a b c : t (t a b) c)
test       = triage "leaf" (\_ : "stem") (\_ _ : "fork")

-- The REPL outputs the tree form results by default; they are elided here.
sapling < test t
DECODE -: "leaf"
sapling < test (t t)
DECODE -: "stem"
sapling < test (t t t)
DECODE -: "fork"
sapling < map (\i : listConcat i " is super cool!") [("He") ("She") ("Everybody")]
DECODE -: ["He is super cool!", "She is super cool!", "Everybody is super cool!"]
```

## Installation

You can easily build and/or run this project using [Nix](https://nixos.org/download/).

- Build REPL binary: `nix build git+https://git.eversole.co/James/sapling`
- Run REPL: `nix run git+https://git.eversole.co/James/sapling`

## Acknowledgements 

Tree Calculus was discovered by [Barry Jay](https://github.com/barry-jay-personal/blog). 

[treecalcul.us](https://treecalcul.us) is an excellent website with an intuitive playground created by [Johannes Bader](https://johannes-bader.com/) that introduced me to Tree Calculus. If sapling sounds interesting but compiling this repo sounds like a hassle, you should check out his site.