(() => {
    'use strict';

    // transpose :: [[a]] -> [[a]]
    const transpose = xs =>
        xs[0].map((_, iCol) => xs.map(row => row[iCol]));


    // TEST -----------------------------------------------
    return(
        transpose([
            [1, 2],
            [3, 4],
            [5, 6]
        ])
    );
})();