libm

A port of MUSL's libm to Rust.

Goals

The short term goal of this library is to enable math support (e.g. sin, atan2) for the wasm32-unknown-unknown target. The longer term goal is to enable math support in the core crate.

Testing

The test suite of this crate can only be run on x86_64 Linux systems.

$ # The test suite depends on the `cross` tool so install it if you don't have it
$ cargo install cross

$ # and the `cross` tool requires docker to be running
$ systemctl start docker

$ # execute the test suite for the x86_64 target
$ TARGET=x86_64-unknown-linux-gnu bash ci/script.sh

$ # execute the test suite for the ARMv7 target
$ TARGET=armv7-unknown-linux-gnueabihf bash ci/script.sh

Contributing

• Pick your favorite math function from the issue tracker.
• Look for the C implementation of the function in the MUSL source code.
• Copy paste the C code into a Rust file in the src/math directory and adjust src/math/mod.rs accordingly. Also, uncomment the corresponding trait method in src/lib.rs.
• Run cargo watch check and fix the compiler errors.
• Tweak the bottom of test-generator/src/main.rs to add your function to the test suite.
• If you can, run the test suite locally. If you can't, no problem! Your PR will be tested automatically.
• Send us a pull request!
• 🎉

Check PR #2 for an example.

Notes

• Only use relative imports within the math directory / module, e.g. use self::fabs::fabs or use super::isnanf. Absolute imports from core are OK, e.g. use core::u64.

• To reinterpret a float as an integer use the to_bits method. The MUSL code uses the GET_FLOAT_WORD macro, or a union, to do this operation.

• To reinterpret an integer as a float use the f32::from_bits constructor. The MUSL code uses the SET_FLOAT_WORD macro, or a union, to do this operation.

• Rust code panics on arithmetic overflows when not optimized. You may need to use the Wrapping newtype to avoid this problem.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.