Use iterators

src/bin/flat.rs

@@ -16,22 +16,27 @@ pub fn main() {
 			gc.canvas_height(1000.0);
 
 			gc.new_path();
+			gc.circle(0.0, 0.0, space.coil_r + space.coil_w + space.coil_m);
 			gc.circle(0.0, 0.0, space.coil_r + space.coil_w);
 			gc.circle(0.0, 0.0, space.coil_r - space.coil_w);
-			gc.line_width(3.0);
+			gc.circle(0.0, 0.0, space.coil_r - space.coil_w - space.coil_m);
-			gc.stroke_color(Color::Rgba(0.8, 0.8, 0.8, 1.0));
+			gc.winding_rule(WindingRule::EvenOdd);
-			gc.stroke();
+			gc.fill_color(Color::Rgba(0.8, 0.8, 0.8, 1.0));
+			gc.fill();
 
 			gc.line_width(1.0);
 			gc.stroke_color(Color::Rgba(1.0, 0.5, 0.0, 1.0));
 			for y in itertools_num::linspace(-1.0, 1.0, 101) {
 				let base = vec2(-500.0, 0.0);
 				let dir = vec2(1.0, y);
-				let path = trace(&space, base, dir, 1000.0, 1.0);
+				let path = trace_iter(&space, base, dir, 1.0);
 				gc.new_path();
 				gc.move_to(base.x, base.y);
-				for pt in path {
+				for pt in path.take(10000) {
 					gc.line_to(pt.x, pt.y);
+					if any(greaterThan(abs(pt), Vec2::from_s(1000.0))) {
+						break
+					}
 				}
 				gc.stroke();
 			}
@@ -89,6 +94,24 @@ trait Metric {
 	}
 }
 
+struct TraceIter<'a, M: Metric> {
+	space: &'a M,
+	p: Vec2,
+	v: Vec2,
+	dt: f32,
+}
+
+impl<'a, M: Metric> Iterator for TraceIter<'a, M> {
+	type Item = Vec2;
+
+	fn next(&mut self) -> Option<Self::Item> {
+		let a: Vec2 = -convolute(krist(self.space, self.p), self.v);
+		self.v = self.v + a * self.dt;
+		self.p = self.p + self.v * self.dt;
+		Some(self.p)
+	}
+}
+
 fn trace(space: &impl Metric, base: Vec2, dir: Vec2, distance: f32, dt: f32) -> Vec<Vec2> {
 	let steps = floor(distance / dt) as usize;
 	let mut result = Vec::with_capacity(steps);
@@ -103,6 +126,32 @@ fn trace(space: &impl Metric, base: Vec2, dir: Vec2, distance: f32, dt: f32) ->
 	result
 }
 
+fn trace_iter<M: Metric>(space: &M, base: Vec2, dir: Vec2, dt: f32) -> TraceIter<M> {
+	TraceIter{
+		space: space,
+		p: base,
+		v: normalize(dir),
+		dt: dt,
+	}
+}
+
+#[test]
+fn t_iter() {
+	let space = Coil {
+		coil_scale: 2.0,
+		coil_r: 300.0,
+		coil_w: 50.0,
+		coil_m: 10.0,
+	};
+	let base = vec2(-500.0, 0.0);
+	let dir = vec2(1.0, 0.3);
+	let dt = 1.0;
+	let steps = 1000;
+	let a = trace(&space, base, dir, dt * (steps as f32), dt);
+	let b: Vec<Vec2> = trace_iter(&space, base, dir, dt).take(steps).collect();
+	assert_eq!(a, b);
+}
+
 fn krist(space: &impl Metric, pos: Vec2) -> Tens2 {
 	// Γ^i_k_l = .5 * g^i^m * (g_m_k,l + g_m_l,k - g_k_l,m)
 	let g = inverse(&space.metric(pos)); // с верхними индексами