import { ddMultDouble2 as ddMultD } from "double-double";


/**
 * Returns the polynomial `f(s·x)`, i.e. the coefficient of `xⁱ` scaled by `sⁱ`.
 *
 * @param p a polynomial with coefficients given densely as an array of double-double
 * precision floating point numbers from highest to lowest power, e.g. `[[0,5],[0,-3],[0,0]]` 
 * represents the polynomial `5x^2 - 3x`
 * @param s the scale factor
 */
function ddScale(
        p: number[][],
        s: number): number[][] {

    const n = p.length - 1;

    const r = new Array<number[]>(n + 1);
    r[n] = p[n];
    let sPow = s;
    for (let i=1; i<=n; i++) {
        r[n - i] = ddMultD(sPow, p[n - i]);
        sPow *= s;
    }

    return r;
}


/**
 * ❗**MODIFIES**❗ the polynomial such that `p(x)` -> `p(s·x)`,
 * i.e. the coefficient of `xⁱ` scaled by `sⁱ`.
 *
 * @param p a polynomial with coefficients given densely as an array of
 * double-double precision floating point numbers from highest to lowest power,
 * e.g. `[[0,5],[0,-3],[0,0]]` represents the polynomial `5x^2 - 3x`
 * @param s the scale factor
 */
function inplaceDdScale(
        p: number[][],
        s: number): void {

    const n = p.length - 1;

    let sPow = s;
    for (let i=1; i<=n; i++) {
        p[n - i] = ddMultD(sPow, p[n - i]);
        sPow *= s;
    }
}


export { ddScale, inplaceDdScale }