Question

Are there any C# libraries out there that provide the same kind of functionality google does when you type in a query such as “13 miles 743 yards in meters” it will return “21 600 meters” (for example).

What I want to be able to do is give a function the string part 13 miles 743 yards and it spits back an int/double with the given distance in meters. It needs to be able to handle all unit input types (kilometers/meters/furlongs/miles/yards/…) but the output only has to be in meters.

It isn’t that hard to write my own, but it would be great to just have a tested library ready to go.

Answer 1

I couldn’t find any answer to this, so I built my own 🙂 The only real ‘magic’ here is the Regex expression to grab the groups of values/units out of the original string. From there it’s simple fraction/number parsing and then working out how many meters each unit represents. I have not tested this much at all, so please let me know if you find improvements or bugs (the code below should throw an exception when it can’t handle a situation).

It won’t handle stupid user input, but provided the format of each section is “[number] [unit]” I think it should work fine. There is not much you can assume if the input doesn’t conform (e.g., 12/32/43 or 1.43.3.2.44 as a value) anyway. I think it will handle extra fluff in the sentence too such as 1 kilometer and 10 miles (will strip out the and). I haven’t added every unit possible, if you know of a complete list of units & there meter equivalent I would love to know about it.

Here are a couple tests,

var a = ExtractDistance("1 1/16 Miles 3/4 yards");
var b = ExtractDistance("02234890234.853 meters");
var c = ExtractDistance("1.8 miles 3.2 furlong");
var d = ExtractDistance("1 kilometer");
var e = ExtractDistance("1/16 Miles");

and here is my code:

private static Dictionary<string, double> _DistanceLookup = new Dictionary<string, double>()
{
  {"mile", 1609.344},
  {"furlong", 201.168},
  {"yard", 0.9144},
  {"inch", 0.0254},
  {"foot", 0.3048},
  {"feet", 0.3048},
  {"kilometer", 1000},
  {"kilometre", 1000},
  {"metre", 1},
  {"meter", 1},
  {"centimeter", 0.01},
  {"centimetre", 0.01},
  {"millimeter", 0.001},
  {"millimetre", 0.001},
};

private static double ConvertFraction(string fraction)
{
  double value = 0;
  if (fraction.Contains('/'))
  {
    // If the value contains /, we need to work out the fraction
    string[] splitVal = fraction.Split('/');
    if (splitVal.Length != 2)
    {
      ScrewUp(fraction, "splitVal.Length");
    }

    // Turn the fraction into decimal
    value = double.Parse(splitVal[0]) / double.Parse(splitVal[1]);
  }
  else
  {
    // Otherwise it's a simple parse
    value = double.Parse(fraction);
  }
  return value;
}

public static double ExtractDistance(string distAsString)
{
  double distanceInMeters = 0;
  /* This will have a match per unit type.
   * e.g., the string "1 1/16 Miles 3/4 Yards" would have 2 matches
   * being "1 1/16 Miles", "3/4 Yards".  Each match will then have 4
   * groups in total, with group 3 being the raw value and 4 being the
   * raw unit
   */
  var matches = Regex.Matches(distAsString, @"(([\d]+[\d\s\.,/]*)\s([A-Za-z]+[^\s\d]))");
  foreach (Match match in matches)
  {
    // If groups != 4 something went wrong, we need to rethink our regex
    if (match.Groups.Count != 4)
    {
      ScrewUp(distAsString, "match.Groups.Count");
    }
    string valueRaw = match.Groups[2].Value;
    string unitRaw = match.Groups[3].Value;

    // Firstly get the value
    double value = 0;
    if (valueRaw.Contains(' '))
    {
      // If the value contains /, we need to work out the fraction
      string[] splitVal = valueRaw.Split(' ');
      if (splitVal.Length != 2)
      {
        ScrewUp(distAsString, "splitVal.Length");
      }

      // Turn the fraction into decimal
      value = ConvertFraction(splitVal[0]) + ConvertFraction(splitVal[1]);
    }
    else
    {
      value = ConvertFraction(valueRaw);
    }

    // Now work out based on the unit type
    // Clean up the raw unit string
    unitRaw = unitRaw.ToLower().Trim().TrimEnd('s');

    if (!_DistanceLookup.ContainsKey(unitRaw))
    {
      ScrewUp(distAsString, "unitRaw");
    }
    distanceInMeters += value * _DistanceLookup[unitRaw];
  }
  return distanceInMeters;
}

private static void ScrewUp(string val, string prop)
{
  throw new ArgumentException("Extract distance screwed up on string [" + val + "] (bad " + prop + ")");
}

Enjoy! I hope someone out there finds this useful. Please leave comments/suggestions.

EDIT: added a , to the regex string to handle 1,300 meters style format