quaeratin/src/double-expansion/e-to-double-double.ts

An extended precision floating point library (as per Shewchuk) - precision only limited by overflow / underflow

import { eCompress } from "./e-compress.js";


// We *have* to do the below❗ The assignee is a getter❗ The assigned is a pure function❗
const compress = eCompress;


/**
 * Returns the result of converting a floating point expansion to a 
 * double-double precision floating point number.
 */
function eToDd(e: number[]) {
    e = compress(e);

    const len = e.length;
    if (len === 2) {
        return e; // already a double-double
    } else if (len === 1) {
        return [0,e[0]]; // double-doubles have a fixed length of 2
    } 
        
    return [e[len-2],e[len-1]]; // return only most significant parts
}


export { eToDd }