quaeratin/test/helpers/is-valid.ts

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

import { isAdjacent } from "../../node/double-expansion/is-adjacent.js";


/**
 * Returns true if the given floating point expansion is non-adjacent and 
 * components of the expansion are ordered in ascending order by absolute value,
 * except that some components may be zero.
 * See https://people.eecs.berkeley.edu/~jrs/papers/robustr.pdf for the 
 * definition of adjacency.
 * Implemented for testing purposes.
 * @param x A floating point expansion.
 */
function isValid(x: number[]): boolean {
    for (let i=1; i<x.length; i++) {
        if (x[i] !== 0 && x[i-1] !== 0 && 
            Math.abs(x[i-1]) >= Math.abs(x[i])) {

            //console.log('Not in ascending order.');
            return false;
        }

        if (isAdjacent(x[i-1], x[i])) {
            //console.log('The expansion has adjacent components.');
            return false;
        }
    }

    return true;
}


export { isValid }