Hydrogen (hy) — a tiny self-hosting-curious language

Milestone 2: Tokenizer · Parser · AST · Generator

🧠 Goal: compile a minimal language statement
exit <int>; → NASM x86-64 assembly → ELF executable → returns that exit code.

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📘 Notion Notes

Part 1: https://l1nq.com/HydrogenPart1NotionNotes

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✨ Features (so far)

🪄 Milestone 1

• Lexer for: return, integer literals, ;
• Direct tokens → NASM (no AST)
• Assembles with nasm + ld
• Demo program returns the chosen exit code (0–255)

⚙️ Milestone 2

• Replaced keyword return → exit
• Introduced a Tokenizer class with peek() + consume()
• Added a Parser + AST
  Grammar:

ExitNode → 'exit' Expression ';' Expression → IntLiteral

• Added a Generator that emits NASM from the AST
• Full pipeline: tokenize → parse → generate → assemble → link → run

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🧩 Requirements

• Linux / WSL (for nasm + ld)
• cmake, g++ or clang++

Install on Ubuntu:

sudo apt update
sudo apt install -y nasm build-essential cmake

🏗️ Build & Run

Using helper scripts:

./scripts/build.sh
./scripts/run.sh
# prints "exit code: 21"

Or manually:

cmake -S . -B build
cmake --build build -j
./build/hydro examples/exit_ok.hy
./out
echo $?

🧠 How it works

1. Tokenize

exit 21;

→ [EXIT, INT_LITERAL(21), SEMICOLON] 2. Parse → AST

Exit {
  Expression {
    IntLiteral(21)
  }
}

3. Generate NASM

global _start
_start:
    mov     rax, 60      ; sys_exit
    mov     rdi, 21      ; exit code
    syscall

4. Assemble + Link

nasm -felf64 out.asm
ld -o out out.o

5. Run

./out
echo $?   # → 21

🧱 Project Structure

Hydrogen/
├─ src/
│  ├─ main.cpp
│  ├─ tokenization.hpp
│  ├─ parser.hpp
│  └─ generation.hpp
├─ examples/
│  └─ exit_ok.hy
├─ scripts/
│  ├─ build.sh
│  └─ run.sh
├─ docs/
│  └─ grammar.md
├─ CMakeLists.txt
└─ README.md

🗓️ Milestone History

Version	Stage	Highlights
v0.1-part1	Minimal compiler	tokens → NASM → ELF
v0.2-part2	Tokenizer + Parser + AST + Generator	full pipeline implemented

🧩 Hydrogen is an educational experiment in building a self-hosting compiler from scratch — one step at a time.