+++
title = 'Os Devlog: Lisp Compiler'
date = 2024-09-08T12:00:00+02:00
categories = ["os"]
tags = ["lowlevel", "lisp", "compiler"]
summary = "LISP :3"
draft = true
+++

## Introduction
In my previous article I wrote about my [os](https://forgejo.vanten-s.com/vanten-s/os). 
In this article I will explore the [compiler I have made for the system](https://forgejo.vanten-s.com/vanten-s/lisp-8bit).

## Goals for the compiler
Goals are important for getting stuff done. With this compiler I want to:
- Implement a simple LISP language 
- Compile to a format that my OS supports
- Functions
- Variables
- Loops
- If statements
- First-class functions

## AST

For the program
```lisp
(+ 1 (+
   a b ))
```
The AST looks like this:
```text
   /  \
  +  /  \
    1  /  \
     /  \ NIL
    +  /  \
      a  /  \
        b   NIL
```

## Compilation
My lisp-implementation is heavily stack-based, and only uses registers when using instructions that need them. 

For example, a + function could compiler to this:
```asm
pop eax
pop ebx
add eax, ebx
push eax
```