I Built a Self-Hosting Language, a DB Engine and a Microkernel — Entirely on My Phone

No laptop. No IDE. Just Termux and a text editor.

Over the past year I shipped five systems from my Android phone:

• SahajCore — a self-hosting programming language
• SahajQL — a natural-language query language
• SahajDB / SahajGame / SahajOS — a DB engine, game engine, microkernel

Here's how the core works.

SahajCore: source → machine

The pipeline is classic:

source → tokenizer → recursive-descent parser → AST
→ tree-walk interpreter
→ bytecode compiler → stack VM
→ C / WAT transpilers

The bytecode compiler emits a flat instruction list. This is real output
from sahajcore --compile:

0004 LOAD a
0005 LOAD b
0006 CONST 2
0007 BIN *
0008 BIN +
0009 STORE c
0014 BIN >
0015 JZ 19

Self-hosting (the fun part)

The interpreter is written in SahajCore itself. The bootstrap chain:

Python-hosted interpreter
→ runs selfhost.sahaj (interpreter written in SahajCore)
→ runs target.sahaj (user program)

The hardest bug: recursive Fibonacci blew the Python stack because every
target-level call expanded into hundreds of host frames. Fix: rewrote the
demo iteratively and raised the recursion limit.

Backends

• C backend: emits C, compile with clang → native binary.
• WASM backend: emits WAT (i32 locals/params, stack ops), assemble with wat2wasm.

SahajDB

A tiny relational engine with:

• Write-Ahead Log (WAL) for durability
• Hash index on primary key
• commit() flushes to disk and clears the WAL

Lessons

1. Constraints focus you. A phone forces small, fast iterations.
2. Write the interpreter in the language itself as early as possible.
3. Test with real programs, not toy examples.

Try it

pip install sahajcore
pip install sahajql

GitHub: github.com/sayan9168/SahajCore

Happy to go deep on any part — ask me anything.