HopHop is a small programming language and reference compiler.

The language is in the C/Go family: plain functions, structs, unions, enums, packages, imports, explicit pointer/reference types, slices, optionals, and compile-time constants. The implementation is still changing, but there's a compiler, library, and test coverage to run real examples through an evaluator, C code generation, native compilation, and wasm.

The compiler is written in strict C11.

hop is a command-line program which loads files, resolves packages, formats source, checks programs, emits code, compiles native executables, and runs programs.

See docs/language.md for the language specification

You need clang, ninja (and python3 for tests) in PATH.

./build.sh

• Products are written to _build/<sys>-<arch>-<mode>/, i.e. _build/macos-aarch64-debug/hop --help
• Run the test suite with ./build.sh test
• Build without the C backend ./build.sh c_backend=0

fn twice(x i32) i32 {
    return x * 2
}

fn main() {
    x := twice(21)
    assert x == 42
    print("hello world")
}

Run with the evaluator:

$ _build/macos-aarch64-debug/hop run examples/hello.hop
hello world

Check (parse, resolve & typecheck) a single file:

$ _build/macos-aarch64-debug/hop check examples/basic.hop

Check a package:

$ _build/macos-aarch64-debug/hop check examples/packages/app
$ _build/macos-aarch64-debug/hop check examples/hello.hop

Transpile to C:

$ _build/macos-aarch64-debug/hop build --output-format c examples/hello.hop -o hello.h

Compile and run through the C11 backend: (will use a C compiler in PATH)

$ _build/macos-aarch64-debug/hop build examples/hello.hop -o hello
./hello

See examples/ for more

See hop --help for usage.

Platform targets:

• cli-libc: native CLI program using the C backend and a small libc platform.
• cli-eval: evaluator runtime used by default for hop run.
• wasm-min: small Wasm host ABI used by tests and smoke runs.
• playbit: Wasm target for Playbit.

build output formats:

• executable builds a usable program and is the default. For cli-libc this is a native executable; for wasm-min and playbit this is a Wasm module.
• c emits C11 text.
• mir, tokens, and ast emit compiler debug text.

For single source-file builds, executable, mir, tokens, and ast default output paths are derived from the source filename, for example hello, hello.mir, hello.tokens, and hello.ast. --output-format c defaults to stdout. Use -o - or --output - to write any build output to stdout explicitly.

Examples:

_build/macos-aarch64-debug/hop build --output-format mir examples/hello.hop
_build/macos-aarch64-debug/hop build --platform wasm-min examples/hello.hop -o hello.wasm
_build/macos-aarch64-debug/hop run --platform wasm-min examples/hello.hop