Question

I want to create a structure Degrees for a GPX library. In the XSD for GPX (GPX 1.1 Schema) degreesType is defined as minInclusive = 0 and maxExclusive = 360. The structure now shall have two public static fields MinValue = 0 and MaxValue = x:

public struct Degrees : IFormattable, IComparable, IComparable<Degrees>, IEquatable<Degrees>
{
    private decimal value;

    public static Degrees MinValue = 0M;
    //public static Degrees MaxValue = x;
}

What is the best way to specify the value of x? 360D-1 would be to inaccurate, 360D-0.001 would be an assumption that no one ever wants a better accuracy than 1/1000 degree.

Answer 1

I can think of two approaches:

• Have your struct faithfully represent
  the fact that the range is specified
  with an inclusive minimum and an
  exclusive maximum; ie, give your
  struct MinInclusive and MaxExclusive
  members. This might be regarded as
  teaching your struct too much about
  the implementation detail of the XSD,
  though

• Define MaxValue as the highest representable decimal value less than 360. Since decimal is a decimal floating point type, we have to be a little careful here, but I think I’m right in saying that since the smallest possible value is 10^-28, and with 360 we have two powers of ten to the left of the decimal point, the relevant value is 360 - 10^-26, or

  const decimal MaxValue = 359.99999999999999999999999999m;
  

  I assume you’re taking care of the conversion from decimal to Degree. Note that the type declaration character for decimal is m or M – d or D is for double.