@extra-array/merge/index.js

Merges values from sorted iterables.

'use strict';

var extraIterable = require('extra-iterable');

/**
 * Finds smallest value.
 * @param x an array
 * @param fc compare function (a, b)
 * @param fm map function (v, i, x)
 * @returns [index, value]
 */
function min(x, fc = null, fm = null) {
    return extraIterable.min(x, fc, fm);
}

/**
 * Merges values from sorted iterables.
 * @param xs iterables
 * @param fc compare function (a, b)
 * @param fm map function (v, i, x)
 */
function merge(xs, fc = null, fm = null) {
    var X = xs.length, a = [];
    if (X === 0)
        return a;
    var is = new Array(X).fill(0);
    var xs = xs.filter(x => x.length > 0);
    while (xs.length > 0) {
        for (var i = 0, I = xs.length, vs = []; i < I; i++)
            vs[i] = xs[i][is[i]];
        var i = min(vs, fc, fm)[0];
        a.push(vs[i]);
        if (++is[i] < xs[i].length)
            continue;
        xs.splice(i, 1);
        is.splice(i, 1);
    }
    return a;
}

module.exports = merge;