INNER CODE UNIT · TypeScript
D
margelo/react-native-graph · src/GetYForX.ts:40
const D = b * b - 4 * a * c;
if (Math.abs(D) < 1e-8) return [-b / (2 * a)];
if (D > 0)
return [(-b + Math.sqrt(D)) / (2 * a), (-b - Math.sqrt(D)) / (2 * a)];
return [];
}
// Convert to depressed cubic t^3+pt+q = 0 (subst x = t - b/3a)
const p = (3 * a * c - b * b) / (3 * a * a);
const q = (2 * b * b * b - 9 * a * b * c + 27 * a * a * d) / (27 * a * a * a);
let roots;
if (Math.abs(p) < 1e-8) {
// p = 0 -> t^3 = -q -> t = -q^1/3
roots = [cuberoot(-q)];
} else if (Math.abs(q) < 1e-8) {
// q = 0 -> t^3 + pt = 0 -> t(t^2+p)=0