/**
 * Returns the exact result of adding two doubles.
 * 
 * * the resulting array is the reverse of the standard twoSum in the literature.
 * 
 * Theorem 7 (Knuth): Let a and b be p-bit floating-point numbers. Then the 
 * following algorithm will produce a nonoverlapping expansion x + y such that 
 * a + b = x + y, where x is an approximation to a + b and y is the roundoff 
 * error in the calculation of x.
 * 
 * See https://people.eecs.berkeley.edu/~jrs/papers/robustr.pdf
 */
function twoSum(a: number, b: number) {
    const x = a + b;
    const bv = x - a;

    return [(a - (x - bv)) + (b - bv), x];
}
// inlined
//const R = a + b; const _ = R - a; const r = (a - (R - _)) + (b - _); return [r,R]

export { twoSum }