import { eSign } from "big-float-ts";
import { expansionProduct } from "big-float-ts";


/** 
 * Returns the exact result (bar underflow / overflow) of multiplying a 
 * polynomial (with coefficients given as Shewchuk floating point expansions) 
 * by a constant (given as a Shewchuk floating point expansion)
 * 
 * @param c a constant (given as a Shewchuk floating point expansion)
 * @param p a polynomial with coefficients given densely as an array of Shewchuk
 * floating point expansions from highest to lowest power, e.g. `[[5],[-3],[0]]` 
 * represents the polynomial `5x^2 - 3x`
 * 
 * @example
 * ```typescript 
 * eMultiplyByConst([0.25], [[3],[2],[1]]); //=> [[0.75], [0.5], [0.25]]  
 * ```
 * 
 * @doc
 */
function eMultiplyByConst(c: number[], p: number[][]): number[][] {
    if (eSign(c) === 0) { return []; }
    
    const d = p.length-1;
    const result = new Array<number[]>(d+1);
    for (let i=0; i<d+1; i++) {
        result[i] = expansionProduct(c, p[i]);
    }
    
    return result;
}


export  { eMultiplyByConst }