Int Code to BitFlag

using System;

using System.Collections.Generic;

class MainClass {

public static ulong CodeToBitFlag(int code) {

//if (code < 0 || code >= 60)

//throw new ArgumentOutOfRangeException("code", "Codes must be between 1 and 59 to avoid overflow problems problems converting to doubles.");

return 1UL << (code - 1);

}

public static List<int> BitFlagToCodes(ulong flag) {

var codes = new List<int>();

var i = 1;

while (flag > 0) {

if ((flag & 1) == 1)

codes.Add(i);

i += 1;

flag = flag >> 1;

}

return codes;

}

static void Main() {

Console.WriteLine(CodeToBitFlag(1));

Console.WriteLine(CodeToBitFlag(2));

Console.WriteLine(CodeToBitFlag(3));

Console.WriteLine(CodeToBitFlag(4));

Console.WriteLine(CodeToBitFlag(5));

Console.WriteLine("--------------------------");

Console.WriteLine(String.Join(",", BitFlagToCodes(1)));

Console.WriteLine(String.Join(",", BitFlagToCodes(2)));

Console.WriteLine(String.Join(",", BitFlagToCodes(4)));

Console.WriteLine(String.Join(",", BitFlagToCodes(8)));

Console.WriteLine("--------------------------");

Console.WriteLine(String.Join(",", BitFlagToCodes(3)));

Console.WriteLine(String.Join(",", BitFlagToCodes(5)));

Console.WriteLine(String.Join(",", BitFlagToCodes(4 | 8)));

Console.WriteLine(String.Join(",", BitFlagToCodes(CodeToBitFlag(3) | CodeToBitFlag(10))));

Console.WriteLine("--------------------------");

Console.WriteLine(String.Join(",", BitFlagToCodes((ulong)((double)(CodeToBitFlag(20) | CodeToBitFlag(41))))));

Console.WriteLine("--------------------------");

for (var i = 2; i < 100; i++) {

ulong f0 = CodeToBitFlag(i-1);

ulong f = CodeToBitFlag(i);

double d = (double)f;

ulong fd = (ulong)d;

if (f != fd) {

Console.WriteLine($"Double mismatch at i={i}; d={d}, f={f}, fd={fd}");

break;

}

if (f < f0) {

Console.WriteLine($"Overflow at i={i}; d={d}, f={f}, fd={fd}");

break;

}

}

for (ulong l = 1UL << 60; l > 1; l++) {

double d = (double)l;

ulong ld = (ulong)d;

if (l != ld) {

var flags = String.Join(",", BitFlagToCodes(l));

Console.WriteLine($"Double mismatch: l={l}, d={d}, ld={ld}, flags={flags}");

break;

}

}

}

}