Welcome to the personal site of Scott Seely

One of the things that is great about integers and longs is that they are easy to remember. However, when using this as identifiers that a human should be able to type in, they leave a lot to be desired. A integer in the billion range requires a user to enter 10 digits correctly. That’s hard to read, hard to keep your place, etc. There is a solution to this issue: represent the data using a radix other than 10. For English speakers, a radix of 36 is easily readable and maximizes the density while allowing for case insensitivity (no one wants to remember if they should type z or Z!).

Consider this, the value for int.MaxValue is written out as:

2147483647

As base 36, it is

zik0zj

6 characters instead of 10. Nice!

To do this, I wrote a simple function that converts a long (64 bits!) to any radix between 2 and 36. This is a basic first or second semester CS problem, I know. Still, this code is handy to have when you need it for converting numbers into something a person can type in:

static string ConvertToString(long value, int toBase)
{
  if (toBase < 2 || toBase > 36)
  {
    throw new ArgumentOutOfRangeException("toBase", 
      "Must be in the range of [2..36]");
  }
  var values = new List<char>();
  for (var val = '0'; val <= '9'; ++val)
  {
    values.Add(val);
  }
  for (var val = 'a'; val <= 'z'; ++val)
  {
    values.Add(val);
  }

  var builder = new StringBuilder();
  bool isNegative = false;
  if (value < 0)
  {
    value = -value;
    isNegative = true;
  }
  do
  {
    long index = value%toBase;
    builder.Insert(0, values[(int)index]);
    value = value/toBase;
  } while (value != 0);
  if (isNegative)
  {
    builder.Insert(0, '-');
  }
  return builder.Length == 0 ? "0" : builder.ToString();
}

And, to go the other way:

static long ConvertToLong(string input, int fromBase)
{
  if (fromBase < 2 || fromBase > 36)
  {
    throw new ArgumentOutOfRangeException("fromBase",
      "Must be in the range of [2..36]");
  }
  if (string.IsNullOrEmpty(input)) return 0;
  input = input.Trim();
  var values = new List<char>();
  for (var val = '0'; val <= '9'; ++val)
  {
    values.Add(val);
  }
  for (var val = 'a'; val <= 'z'; ++val)
  {
    values.Add(val);
  }

  var builder = new StringBuilder();
  bool isNegative = false;
  int startIndex = 0;
  if (input[0] == '-')
  {
    isNegative = true;
    ++startIndex;
  }
  long retval = 0;
  for(int index = startIndex; index < input.Length; ++index)
  {
    retval *= fromBase;
    bool found = false;
    for (int number = 0; number < fromBase; ++number)
    {
      if (input[index] == values[number])
      {
        retval += number;
        found = true;
      }
    }
    if (!found) break;
  }
  if (isNegative)
  {
    retval = -retval;
  }
  return retval;
}