cross.ts

import type { FnU2 } from "@thi.ng/api";
import type { ReadonlyVec, Vec } from "./api";
import { setC3 } from "./setc";

export const cross2: FnU2<ReadonlyVec, number> = (a, b) =>
    a[0] * b[1] - a[1] * b[0];

export const cross3 = (out: Vec | null, a: ReadonlyVec, b: ReadonlyVec) =>
    setC3(
        out || a,
        a[1] * b[2] - a[2] * b[1],
        a[2] * b[0] - a[0] * b[2],
        a[0] * b[1] - a[1] * b[0]
    );