Composable numerical methods for Rust.

use numra::ode::{solve_ivp, Tsit5};
use numra::prelude::*;

// Lorenz system: dx/dt = σ(y - x), dy/dt = x(ρ - z) - y, dz/dt = xy - βz
let lorenz = |_t: f64, y: &[f64], dy: &mut [f64]| {
    let (s, r, b) = (10.0, 28.0, 8.0 / 3.0);
    dy[0] = s * (y[1] - y[0]);
    dy[1] = y[0] * (r - y[2]) - y[1];
    dy[2] = y[0] * y[1] - b * y[2];
};

let sol = solve_ivp(lorenz, (0.0, 40.0), &[1.0, 1.0, 1.0])
    .method(Tsit5::new())
    .rtol(1e-8)
    .atol(1e-10)
    .dense_output(true)
    .run()?;