クロージャを渡す実装をしました。 t
の引数は結局使ってないので削除しました。
error[E0277]: the size for values of type `(dyn std::ops::Fn(f64, f64) -> f64 + 'static)` cannot be known at compilation time --> src/main.rs:31:32 | 31 | fn runge_kutta(x: f64, v: f64, f: Fn(f64, f64) -> f64) -> (f64, f64) { | ^ doesn't have a size known at compile-time
…なのですが、今のところ意味が分からずに書いてるので後でチェックします。
use gnuplot::{Figure, Caption, Color}; const K: f64 = 1.0; const M: f64 = 1.0; const A: f64 = 2.0; const X0: f64 = 0.0; const V0: f64 = 1.0; const DELTA_T: f64 = 0.01; fn main() { let (mut x, mut v) = (X0, V0); let mut xs = vec![]; let mut ts = vec![]; for i in 1..1000 { let t = (i as f64) * DELTA_T; let (dx, dv) = runge_kutta(x, v, |x, v| { - K * x - A * v }); x += dx; v += dv; ts.push(t); xs.push(x); } plot(ts, xs); } fn runge_kutta<F>(x: f64, v: f64, f: F) -> (f64, f64) where F : Fn(f64, f64) -> f64 { let k1v = f(x, v) * DELTA_T / M; let k1x = v * DELTA_T; let k2x = (v + k1v / 2.0) * DELTA_T; let k2v = f(x + k1x / 2.0, v + k1v / 2.0) * DELTA_T / M; let k3v = f(x + k2x / 2.0, v + k2v / 2.0) * DELTA_T / M; let k3x = (v + k2v / 2.0) * DELTA_T; let k4v = f(x + k3x, v + k3v) * DELTA_T / M; let k4x = (v + k3v) * DELTA_T; let v = (k1v + 2.0 * k2v + 2.0 * k3v + k4v) / 6.0; let x = (k1x + 2.0 * k2x + 2.0 * k3x + k4x) / 6.0; (x, v) } fn plot(x: Vec<f64>, y: Vec<f64>) { let mut fg = Figure::new(); fg.set_terminal("pngcairo", "output.png"); fg.axes2d() .lines(&x, &y, &[Caption("A line"), Color("black")]); fg.show(); }