cayley - generic, stack-allocated linear algebra in Rust

cayley is a crate that fills a small niche: it provides a generic matrix type that allocates its data on the stack. This makes cayley pretty quick even on very large scales. It also handles slightly more complex operations on matrices, such as finding the determinant and inverse of a matrix. These calculations are not very optimised as of now, but at least they exist. cayley is named after Arthur Cayley, a prominent mathematician who introduced matrix multiplication.

One of the major features of this crate (and at the time of writing its greatest drawback too) is that it uses the generic_const_exprs feature. This is experimental Rust, but it allows a type-safe dimensionality system. Take, for example, matrix multiplication. A 4 by 3 matrix can't be multiplied by a 7 by 5 one. I wasn't able to find any other crate that's able to check that at compile time. cayley does. It's impossible to compile code that will try to perform a matrix operation which shoudln't be possible. The hindrance is that Rust's type inference doesn't fully support generic constant expressions (yet) and as a result the user has to explicitly annotate the dimensions of the Matrix type, like so:

use cayley::Matrix;

let m1: Matrix<f64, 2, 3> = Matrix::ones(2, 3);
let m2: Matrix<f64, 3, 2> = Matrix::from_closure(3, 2, |x, y| (x + y) as f64);

let m3: m1 * m2; // compile-time multiplication checks!

As you can see in the example above, cayley's matrices are generic. The crate was designed with as much type flexibility in mind. To give an example, for two matrices of different types T and Q to be multiplyable, there needs to exist a 'tensor type' R so that an implementation of Mul<Q, Output = R> exists on T and an implementation of Add exists on R. For sensible numerical types these implementations are automatically handled by the num_traits crate (which, incidentally, handles a lot of the mathematical logic in cayley).

Contributions

I'm but a humble seventeen-year-old high schooler from Belgium who likes to write code in their free time. If you feel like helping out, feel free to do so!