this rename is absolutely stupid

docs/chapters/inflections/inflection.js

@@ -0,0 +1,62 @@
+setup() {
+    const curve = this.curve = new Bezier(this, 70,250, 120,15, 20,95, 225,80);
+    setMovable(curve.points);
+}
+
+draw() {
+    clear();
+
+    const curve = this.curve;
+    curve.drawSkeleton();
+    curve.drawCurve();
+    curve.drawPoints();
+
+    const p = curve.align().points,
+
+          a = p[2].x * p[1].y,
+          b = p[3].x * p[1].y,
+          c = p[1].x * p[2].y,
+          d = p[3].x * p[2].y,
+
+          x = -3*a + 2*b + 3*c - d,
+          y = 3*a - b - 3*c,
+          z = c - a,
+
+          roots = [];
+
+    if (this.almost(x, 0) ) {
+      if (!this.almost(y, 0) ) {
+        roots.push(-z / y);
+      }
+    }
+
+    else {
+        const det = y * y - 4 * x * z,
+              sq = sqrt(det),
+              d2 = 2 * x;
+
+        if (!this.almost(d2, 0) ) {
+            roots.push(-(y+sq) / d2);
+            roots.push((sq-y) / d2);
+        }
+    }
+
+    setStroke(`red`);
+    setFill(`red`);
+
+    roots.forEach(t => {
+        if (0 <= t && t <= 1) {
+           let p = curve.get(t);
+           circle(p.x, p.y, 3);
+           text(`t=${t.toFixed(2)}`, p.x + 5, p.y + 15);
+        }
+     });
+}
+
+almost(v1, v2, epsilon=0.00001) {
+    return abs(v1 - v2) < epsilon;
+}
+
+onMouseMove() {
+    redraw();
+}