A typed programming language for AI.

Edit individual functions with revision-checked patches. Compile to native code, WebAssembly, C and other targets.

> curl -fsSL https://raw.githubusercontent.com/Joe-Simo/a0/main/install.sh | sh

PS> irm https://raw.githubusercontent.com/Joe-Simo/a0/main/install.ps1 | iex

View install script Then follow the quick start

Source tokens

29 fixed benchmark programs · o200k_base

A09,028

C6,402

JavaScript6,400

Rust6,565

0 → 10,000 tokens · lower is better

Exact source counts and method →

Small programs, compiled

Time per call as a multiple of A0's · geometric mean · log scale · shorter is faster

0.86x

Rust

0.93x

C++

0.94x

1.00x

Zig

1.11x

Java

1.30x

TypeScript

1.40x

1.53x

1.57x

OCaml

2.72x

JavaScript

5.77x

Forth

15.3x

PHP

19.6x

Lua

19.6x

Ruby

73.9x

Python

169x

3 of 48 languages within 5% of A0; 8 faster

− Slower than the best of C, Rust and Zig on 8 of 19 programs, worst 4.31x (mat4)

Source: results/exec-benchmark-full.json · method →

Whole-program check, fresh process

A0's front end against TypeScript's checkers · median ms · lower is better

macOS arm64 · load average at most 10.0, limit 10.0 · check-latency-darwin-arm64.json

72.6

tsc

530.5

tsgo

56.7

tsc-rs

53.7

Linux x64 · load average at most 1.2, limit 10.0 · check-latency-linux-x64.json

69.2

tsc

872.4

tsgo

120.3

tsc-rs

86.0

Windows x64 · CPU use at most 8.0, limit 10.0 · check-latency-win32-x64.json

847.1

tsc

3918.1

tsgo

25651.8

A0 against 8 checker runs: 5 faster, 1 tied, 2 slower

− macOS arm64: tsgo 56.7 ms, A0 72.6 ms
− macOS arm64: tsc-rs 53.7 ms, A0 72.6 ms

Source: results/check-latency-*.json · method →

WebAssembly, against clang -O3

19 programs · Windows x64 · CPU use at most 8.0, limit 10.0

Module bytes, summed · lower is better

9336

clang

11394

Time per trip as a multiple of A0's · geometric mean

1.00x

clang

1.08x

Per program: 7 faster, 7 tied, 5 slower

− Slower than clang on 5 of 19 programs, slowest at 0.78x
− Larger module on 1 of 19 programs

Source: results/wasm-benchmark.json · method →

01 / Language and tools

Write, check and compile.

Language

Typed functions

Every function states its types. One operation per line.

a0 check sq.a0

Edits

Revision-checked patches

Change instructions or replace a function. A0 checks the patch before applying it.

a0 patch sq.a0 edit.patch

Targets

C, arm64, WebAssembly

Compile the same source to different targets. See the benchmarks for verification coverage.

a0 emit arm64 sq.a0

Agents

MCP server

Open function views, apply patches, run checks and save changes through MCP.

a0 mcp .

02 / Quick start

Run your first function.

printf 'fn sq u32 -> u32\na mul p0 p0\nret a\nend\n' > sq.a0
One typed function.
a0 run sq.a0 sq 12
Prints 144.
a0 check sq.a0
Reports type and bounds errors. --fix applies supported diagnostic fixes.
a0 emit arm64 sq.a0
Emits ARM64 machine code. Other targets include C, JavaScript, Java and SystemVerilog.
a0 mcp .
Serves the folder to an agent over MCP.

Full list in the CLI reference.

03 / Limits

Limits and benchmark results.

Loss	Measured	Source
Native speed against the best of C, Rust and Zig	slower on 8 of 19 programs, worst 4.31x	exec-benchmark-full.json
What the language lacks	floats, heap, recursion	STATUS.md

04 / Install

Install

> curl -fsSL https://raw.githubusercontent.com/Joe-Simo/a0/main/install.sh | sh

Quick start Source on GitHub ↗