+line-handled

src/ex.rs

@@ -58,6 +58,31 @@ pub fn dumbbell(a: f64, p: f64) -> impl Fn(f64) -> [f64; 2] {
     }
 }
 
+pub fn line_handled(a: f64) -> impl Fn(f64) -> [f64; 2] {
+    let ap2 = a + 2.0;
+
+    move |t: f64| {
+        if t <= 0.25 {
+            let tm4 = t * 4.0;
+            let tt2pi = tm4 * TAU;
+            let (ttsin, ttcos) = tt2pi.sin_cos();
+            [ttcos, ttsin]
+        } else if t <= 0.5 {
+            // start at (1, 0)
+            let tm4 = (t - 0.25) * 4.0;
+            [1.0 + tm4 * a, 0.0]
+        } else if t <= 0.75 {
+            let tm4 = 1.5 - (t - 0.5) * 4.0;
+            let tt2pi = tm4 * TAU;
+            let (ttsin, ttcos) = tt2pi.sin_cos();
+            [ap2 + ttcos, ttsin]
+        } else {
+            let tm4 = 1.0 - (t - 0.75) * 4.0;
+            [1.0 + tm4 * a, 0.0]
+        }
+    }
+}
+
 pub fn ellipse(a: f64, b: f64) -> impl Fn(f64) -> [f64; 2] {
     move |t: f64| {
         let cdat = circle(t);

src/lib.rs

@@ -13,6 +13,7 @@ pub enum SelectExample {
     CassiniAstroidTsq { ca: f64, cc: f64, aa: f64 },
 
     Dumbbell { a: f64, p: f64 },
+    LineHandled { a: f64 },
     Ellipse { a: f64, b: f64 },
     Lemniskate { a: f64 },
     CirclePow { k: f64 },
@@ -46,6 +47,9 @@ impl SelectExample {
             Self::Dumbbell { a, .. } => {
                 *a += l;
             }
+            Self::LineHandled { a } => {
+                *a += l;
+            }
             Self::Ellipse { a, b } => {
                 *a /= 1.0 + l;
                 *b *= 1.0 + l;
@@ -84,6 +88,7 @@ impl SelectExample {
                 Box::new(move |t: f64| x(t * t))
             }
             Self::Dumbbell { a, p } => Box::new(ex::dumbbell(a, p)),
+            Self::LineHandled { a } => Box::new(ex::line_handled(a)),
             Self::Ellipse { a, b } => Box::new(ex::ellipse(a, b)),
             Self::Lemniskate { a } => Box::new(move |t: f64| ex::lemniskate(t, a)),
             Self::CirclePow { k } => Box::new(ex::circle_pow(k)),