hourformat.d

import std.stdio;
import std.string;
import std.algorithm;

void main()
{
    auto formatHour = (int x) => "%02d".format(x);

    auto hours = [0 : "00", 6: "06", 10: "10", 59: "59"];
    assert(all!(h => formatHour(h) == hours[h])(hours.keys));
}