Small, quick, sharp. A programming language on LLVM with C-like syntax, simple enough to learn in an hour and as fast as C.

🇵🇱 Polska wersja

import "math.h"

fn hypot2(float a, float b) -> float {
    return sqrt(a * a + b * b)
}

fn main() {
    name := "Finch"
    print("Hello from", name, "!")

    for i in 1..4 {
        print(i, "→", hypot2(float(i), 1.0))
    }
}

Why Finch

• Simple. No semicolons, no headers, no preprocessor. Each thing has one way to do it.
• Fast. It compiles through LLVM's -O2 pipeline to native code, with no garbage collector. Recursive fib(40) runs in about 0.19 s (clang -O2 on the same C: about 0.23 s); bounds-checked array code matches C.
• Memory without the pain. Lists, text and structs are values: assigning copies, and the end of a block frees them. There is no free to forget, no use-after-free, and every test is clean under valgrind.
• Safer than C, where it is cheap. No silent narrowing and no signed/unsigned mixing. Out-of-range indexes, division by zero and null pointers stop with a clear runtime error instead of undefined behavior. Operator precedence that does not bite (x & 1 == 0 means what it says).
• Practical. Maps, methods, errors as values (int(s) or 0, try read_file(p)), modules, any C library, and a language server for your editor. Runs on Linux, macOS and Windows, on x86-64 and ARM64.
• SIMD built in. f32x8, i8x32, f64x4: numbers side by side, added and multiplied all at once. LLVM turns them into SSE, AVX2, AVX-512 or NEON instructions, so one piece of code is fast on a desktop, a laptop and ARM.
• Errors that talk like a person:

  game.fch:3:13: error: 'y' must be i32, but this is int (use i32(...) to convert)
      3 |     i32 y = x
        |             ^
  

• Any C library, directly. import "raylib.h" + link "raylib", and you can call it, structs by value and callbacks included. Headers are read by libclang, so there is nothing to declare by hand.
• Written in itself. The compiler is Finch code, and nothing else: src/*.fch, about 12k lines. It is built from a seed (its own LLVM IR, bootstrap/) and then from itself, and the two come out identical.

Quick start

Ready builds for Linux (x64, ARM64), macOS (Apple Silicon, Intel) and Windows (x64) are in the releases. Unpack one and keep runtime/ and std/ next to finch. What each system needs besides is in the technicians' guide: clang and libclang from LLVM 21 on Linux, brew install llvm@21 on a Mac, llvm-mingw on Windows.

Building it yourself (on Linux, macOS, or Windows with Git Bash; needs clang and libclang, LLVM 21):

git clone https://github.com/Nexoniarz/Finch.git
cd Finch
nix-shell                           # or install clang + libclang (LLVM 21) + pkg-config yourself
bootstrap/build.sh                  # the compiler is build/finch: built from the seed, then from itself

./build/finch run examples/hello.fch
./build/finch build examples/tour.fch -o tour && ./tour
tests/run.sh                        # every program, every expected error, -g, a shared library, the language server

The same bootstrap/build.sh works on a Mac (with Homebrew's llvm@21) and on Windows (with llvm-mingw): see bootstrap/README.md. Programs for another system are built with --target windows|linux|arm64|macos (see the guide).

Editors: Kate (editors/kate/install.sh), VS Code (the finch-lang .vsix from the release), or any editor with LSP support (finch lsp).

Documentation

Pick the guide that fits you:

Guide	For	English	Polski
Beginners	Never programmed: students, seniors, anyone curious	for-beginners.md	dla-poczatkujacych.md
Technicians	Know computers, new to programming: install, whole language, C libraries, troubleshooting	for-technicians.md	dla-technikow.md
Engineers	Everything: lexer, grammar, AST, type rules, IR lowering, libclang import, ABI, internals	for-engineers.md	dla-inzynierow.md
Cheat sheet	Every function, method, operator and command on one page	cheatsheet.md	sciaga.md

The language at a glance

Variables	x := 5 (inferred) or int x = 5; const W = 640
Types	int float bool char str, sized i8…i64 u8…u64 f32 f64, arrays []T, maps map[K]V, pointers ptr[T], vectors f32x8 i8x32…
Functions	fn add(int a, int b) -> int { return a + b }
Structs	struct Point { … } with one field per line (int x, int y = 0); create with Point(1, 2) or Point(x: 1)
Methods	fn Point.move(int dx) { self.x += dx } → p.move(3)
Arrays	nums := [1, 2, 3], nums.push(4), nums[0], nums.len, for i, n in nums { }
Maps	ages := ["ann": 31], ages["bob"] = 25, ages.has("cy"), counts[w] += 1, for k, v in ages { }
Errors	fn parse(str s) -> int! { … return error("bad") } → parse(s) or 0, parse(s) or { … }, try parse(s)
Vectors (SIMD)	v := f32x8(list, i), v * 2.0 + w, v.sum(), v.dot(w), min(v, 1.0), v.store(list, i), v[3]
Text	"hp \(hp)", "a" + "b", str(42), int("42"), s.split(","), s.upper(), s[0]
Control	if / else if / else (also as a value), while, for i in 0..10, break, continue, defer
Memory	automatic for arrays, text and structs; new(...) / free(...) for your own heap structures
Enums, match	enum Color { Red, Green }, match c { Red -> ... else -> ... } (also as a value)
Generics	fn max[T](T a, T b) -> T, struct Stack[T], Stack[int]()
Modules	import shapes → shapes.area(b), import ui/button as btn; the standard library: json, path, time, proc, fs, thread
Threads	thread.spawn(addr(work), addr(data)), t.join(), thread.mutex(), atomic_add(addr(n), 1)
Tests	test "name" { assert(x == 3) } next to the code, run with finch test
C interop	import "stdio.h", link "glfw", link "mine.c" / "glue.cpp", unions, #defines (also (Color){…}), addr(fn) for callbacks
I/O	print(...), input("? "), read_file, write_file, shell
Tools	finch run/build/test/fmt/ir/lsp, finch.toml for a project, a build cache, --target windows/arm64/macos/android, --cpu native, -g for gdb/lldb, -O0, the chain of calls on runtime errors

Examples

File	Shows
examples/hello.fch	the smallest program
examples/tour.fch	variables, functions, conditions, loops
examples/guess.fch	a guessing game: input, loops, C's rand
examples/todo.fch	structs, arrays, strings and files
examples/wordcount.fch	maps, methods and errors as values: the most frequent words in a file
examples/structs.fch	structs, arrays of structs, a linked list with new/free
examples/types.fch	sized numbers and pointers
examples/c_import.fch	printf, math.h, malloc/free, stderr
examples/simd.fch	vectors: a dot product eight numbers at a time, and the time it saves
examples/window.fch	a GLFW + OpenGL window
examples/opengl.fch	modern OpenGL 3.3: shaders, buffers, a spinning triangle
examples/vulkan.fch	Vulkan: list the GPUs, their memory and queues, create a device
examples/raylib.fch	raylib with C structs by value
examples/llvm.fch	Finch building LLVM IR through the LLVM-C API
src/	the compiler, written in Finch (the seed to build it is in bootstrap/)

Roadmap

• Lexer, parser, LLVM codegen, O2 optimization
• Types incl. sized integers, pointers, conversions; functions; if/while/for
• Readable compile errors; runtime checks (division, null, bounds)
• Bitwise operators with sane precedence
• C headers through libclang; link with pkg-config; link-error advice
• struct, including C structs by value (System V ABI) and callbacks
• Arrays with .len, bounds checks and methods; for x in list
• Memory: values freed at the end of their block, defer, new/free
• Strings: +, .len, indexing, methods, str(x), int(s); input(); files
• Finch modules (import name)
• Debug info (-g)
• Bootstrap: a Finch compiler written in Finch that builds itself
• Windows: finch.exe, .exe programs, the Microsoft x64 ABI; cross-building from Linux (--target windows)
• Language server (finch lsp) and a VS Code extension
• macOS and ARM64 (Linux and Apple Silicon), with their C calling conventions; Kate support
• Methods on structs, maps, errors as values (!, or, try)
• Generics (fn max[T], struct Stack[T]), match, enums
• A standard library in Finch: json, path, time, proc, fs
• const, if as a value, "\(x)" in text, """ text, C unions and #define expressions
• test blocks and finch test, finch fmt, finch.toml, a build cache, the chain of calls on runtime errors
• Threads (import thread) and atomics; C++ files; --target android
• The compiler on every system it builds for: Linux, macOS (Apple Silicon and Intel), Windows; releases made by CI
• Vector types (f32x8, i8x32, …) for SIMD, and --cpu native

Layout

src/        the compiler, in Finch: lexer, parser, AST, code generation (to LLVM IR as text), C import (libclang) and
            the C calling conventions, the language server, the driver
std/        the standard library, in Finch: json, path, time, proc, fs, thread
runtime/    the small C runtime linked into every program
bootstrap/  build.sh and the seeds: the compiler's own LLVM IR, one per system
examples/   example programs
editors/    VS Code extension, Kate highlighting and LSP setup
tests/      run/ new/ (golden output), fail/ new/fail/ (expected errors), run.sh, cross.sh, shared.sh, lsp_test.py
docs/       en/ and pl/ guides for three audiences

License

Apache License 2.0. Copyright 2026 Nexoniarz.