fx

Version: 0.7.1
Copyright © 2026 Shawn Londono · LedoCorp · http://www.ledocorp.org
License: Apache License 2.0 · NOTICE

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What fx is

fx is a systems language that refuses hidden control.

No garbage collector quietly rewriting your heap.
No implicit allocator.
No framework magic between what you wrote and what runs.

Every important decision (who allocates, who mutates, how long memory lives) is visible in the source.

fx is built for people who still live in the C universe (or need to) and want a sharper language on top of it, not a replacement religion:

You care about…	fx’s answer
Predictable memory	Named regions + effects (alloc, mut) in the signature
Shipping beside C	Dual emission: run natively and emit readable C
Existing C libraries	Wrap / host: C owns main, fx owns the logic
Auditability	Lowering targets a small, explicit C substrate (zspec)
Humans and agents	Low-ceremony, local style: easy to read, easy to generate, hard to “accidentally GC”

This repository is the full language package: compiler binary, standard library, scaffolds, docs, link materials, and optional inspectable compiler sources under compiler-source/. Clone it, put bin/ on your PATH, and write fx. To read how the frontend is expressed in fx, open compiler-source/ (that folder is not a rebuild SDK).

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The idea in one screen

import std/vec;

fn main() -> i32 effects { alloc, mut } {
    region r = arena(4096);              // this heap lives here
    let v: Vec<i32> = vec.new(0);
    let v2: Vec<i32> = vec.push(v, 40);
    let v3: Vec<i32> = vec.push(v2, 2);
    return vec.get(v3, 0) + vec.get(v3, 1);  // 42
}

When r ends, that arena is gone. The effects clause told you the function may allocate and mutate before you read the body. That is the product: locality of reasoning.

When you need the C world:

fx emit-c main.fx -o out_c          # inspect the lowering
fx run lib.fx --host host.c         # C main + fx library

Emitted C is not a dump of IR. It is meant to look like something a competent C programmer could maintain.

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Who fx is for

• Systems and embedded developers who want structure without surrendering the heap to a GC
• Teams wrapping mature C libraries who want a better language for new code, not a full rewrite
• People building with AI assistants who need a language that stays mechanical and explicit so generated code remains auditable

It is not trying to be a batteries-included application platform, a GC scripting language, or a marketing-site ecosystem. This release ships a serious core: language + compiler + std foothold + C interop.

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Quick start

Requirements: this repo · a C toolchain (gcc default) · Windows or Linux x86_64 (macOS binary comes later).

# put bin/ on PATH, then:
fx doctor                  # check gcc/clang/zig + zspec paths
fx version                 # v0.7.1
fx new hello
cd hello
fx run main.fx             # exit 42

OS	Binary
Windows	bin/fx.exe
Linux	bin/fx

More: docs/START_HERE.md

fx new tiny --scaffold minimal
fx new firmware --scaffold embedded

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What you get in this package

Path	Role
bin/	Prebuilt fx compiler
scaffolds/	Official fx new templates
std/	Standard library (import std/vec, …)
zspec/ + build/	Headers + libzspec for linking emitted C
docs/	Language and tooling guides
examples/	Optional demos (core + C-host wrap)
compiler-source/	Read-only fx compiler modules (inspect; run bin/fx)

Map: PACKAGE.md

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Dual emission & C interop

fx treats C as a first-class destination, not an escape hatch:

• fx run / fx build: emit, link with zspec, run or produce a binary
• fx emit-c: generate .c / .h you can read and own
• --host: keep your C main, link fx as the library

Demo:

fx run examples/showcase_wrap/compute.fx --host examples/showcase_wrap/host.c

→ docs/WRAP.md · docs/CLI.md

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Language guides

Also on the web: https://www.ledocorp.org/fx/docs/

Doc	Topic
docs/LANGUAGE.md	Language tour (types, Result, collections, modules, …)
docs/REFERENCE.md	Compact 0.7 surface reference
docs/REGIONS.md	Effects, region kinds, ownership / borrows
docs/STD.md	Standard library map and APIs
docs/WRAP.md	C host / extern "c"
docs/SCAFFOLDS.md	Project templates
docs/CLI.md	Full command surface (incl. fx doctor / fx lsp / fx mcp)
docs/START_HERE.md	Install and hello

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Tooling for humans and agents

This package’s compiler includes:

• fx doctor: check C toolchain + zspec paths
• fx lsp: editor language server
• fx mcp: lean MCP tools for agents (check / locate / run, …)

Same explicit language, usable from Cursor and friends once fx is on your PATH.

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Contributing & security

fx is stewarded by Shawn Londono / LedoCorp.

• GitHub pull requests are not accepted at this time.
• Issues are welcome for bugs.

See CONTRIBUTING.md and SECURITY.md.

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Release note

0.7.1 is a usable language package: compiler, scaffolds, std foothold, Windows/Linux binaries, C wrap path, fx doctor, expanded language docs (aligned with ledocorp.org), and inspectable compiler-source/. The standard library is still small; macOS binaries will follow.

The thesis is not small: explicit systems programming with dual emission to readable C.