export default function extE2(a0: number, a1: number, a2: number, a3: number, b0: number, b1: number, b2: number, b3: number, index: number): number {
    a0 = +a0;
    a1 = +a1;
    a2 = +a2;
    a3 = +a3;
    b0 = +b0;
    b1 = +b1;
    b2 = +b2;
    b3 = +b3;
    index = index | 0;
    var x = 0.0;
    switch (~(~index)) {
        case 0: {
            x = +(a0 * b0);
        }
            break;
        case 1: {
            x = +(a0 * b1 + a1 * b0);
        }
            break;
        case 2: {
            x = +(a0 * b2 + a2 * b0);
        }
            break;
        case 3: {
            x = +(a0 * b3 + a1 * b2 - a2 * b1 + a3 * b0);
        }
            break;
        default: {
            throw new Error("index must be in the range [0..3]");
        }
    }
    return +x;
}