Monad
[!WARNING]
Monad is in alpha release and under heavy development. Many features are
not implemented yet and are not tested properly. Expect breaking changes,
incomplete functionality, and potential bugs.
The Maturity Matrix says, area by
area, what actually works today.
A purely functional, dependently typed systems programming language that
compiles to native binaries through LLVM. The compiler is written in Monad
and compiles itself.
Homepage: monad-lang.org
Why Monad?
- Dependent types — types can depend on values, with a
Prop universe
and propositional equality for compile-time proofs
- Type classes — ad-hoc polymorphism with automatic instance resolution
- Termination checking — recursive definitions must be structurally
decreasing unless you opt out
- Hygienic macros —
defmacro, quote, and compile-time reflection;
#[derive] is implemented in Monad, not in the compiler
- LLVM native — programs compile to fast native binaries, no VM
- Self-hosting — the compiler in
lang/ is written in Monad and compiles
itself, reaching a fixpoint where the binary builds its own successor
Install
curl -fsSL https://monad-lang.org/install | bash
export PATH="$HOME/.monad/bin:$PATH"
monadup default # install the latest nightly and make it active
monadup doctor # check the compiler and the LLVM/GC build prerequisites
monad version
monadup is a Monad-written binary. It manages nightly builds under
~/.monad; use monadup list, monadup use <tag>, monadup update, and
monadup uninstall <tag> to manage installed versions. monadup env prints
the resolved environment, monadup doctor --json is the machine-readable
health report an agent can act on, and monadup new hello scaffolds a project.
Nightlies are published for x86_64-linux and aarch64-darwin (built
natively), plus cross-built aarch64-linux and experimental riscv64-linux.
The Linux binaries are fully static and the macOS one links only libSystem;
compiling a Monad program still needs llc, clang and Boehm GC on the
machine, which monadup doctor checks for you.
Build from source
git clone https://tangled.org/monad-lang.org/monad
cd monad
devenv shell # provides Rust, clang, llc, Boehm GC, mdbook
cargo build --release
cargo run --release -- run cli/src/main.mo build cli/src/main.mo -o "$PWD/monad" --release
The compiler the flake builds is published to the project's Cachix cache. A
nix build --accept-flake-config .#monad reads it with no setup; cachix use monad-lang opts in permanently by adding the substituter to your nix.conf, so
an unchanged rung is a substitution rather than a ~20 minute interpretation.
The -o must be absolute: a relative output name lands in the compiler's
scratch directory. The trailing --release turns off DWARF debug info, which
is on by default.
Quick start
use std::io {}
open IO {println}
def main (args : List String) : IO Unit := println "Hello, World!"
Save that as hello.mo, then:
monad run hello.mo
monad run compiles and executes in one step — a Monad program is always a
native binary. To keep the binary, use monad build with an absolute output
path:
monad build hello.mo -o "$PWD/hello"
./hello
Commands
monad build [<path>] [name] [--bin <name>] [--output/-o <name>] [--verbose/-v] [--debug/-g] [--release]
Parse, type-check and compile a source file, or a mote's [[bin]] target,
to a native binary. --bin picks one of several.
monad install [<path>] [-o <name>] [--bin <name>] [--target <triple>] [--verbose/-v] [--no-cache]
Build a RELEASE binary and install it to $MONAD_HOME/bin (default
$HOME/.monad/bin), replacing the destination atomically.
monad run <path> [--verbose/-v] [--debug/-g] [--release]
Compile and execute. The program's exit code becomes monad's.
monad eval <path> [--verbose/-v]
Evaluate with the built-in interpreter. Pure programs only.
monad repl
Interactive loop over the same interpreter; expressions print
value : type and declarations/use persist in a session.
monad check [<path>...] [--workspace/-w] [--verbose/-v]
Parse and type-check; no execution.
monad test [<path>...] [--workspace/-w] [--verbose/-v]
Compile each file's #[test] defs and run them.
monad pretty <path>
Parse and pretty-print a .mo source file.
monad version
Print the git commit this binary was built from.
Running monad with no arguments prints usage. Directory arguments are
expanded recursively; with no path, commands operate on the mote containing
the working directory, and --workspace covers every mote in the workspace.
Community
Documentation
The full documentation lives at monad-lang.org —
built with mdBook from docs/src/, with every code block type-checked by CI.
Key pages:
License
Apache 2.0
