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Jon Skeet
Why does SortedSet<T> ignore CompareTo() values of 0 by default?
When I try to AddRange to a SortedSet, it doesn't add values when their compareto result is zero. This doesn't make any sense to me, as it's not a SortedSet of the values that compareTo is comparing, it's a SortedSet of T. I am trying to understand why Microsoft would implement it like this.
- Is there any logical explanation to this that will help me remember in the future?
- Is the correct way to implement IComparable on my type by not returning 0 from CompareTo? What happens if I need CompareTo to determine equality explicitly when I use its IComparable.CompareTo() method elsewhere in my code?
The whole point of the comparison is to say whether one item is greater than, less than or equal to another. A set doesn't allow equal values - and in a sorted set, equality is defined by the comparison. It's as simple as that.
For your second question, it sounds like you want to have two different comparisons - one which returns 0 in certain cases where the other one wouldn't. You can do that by implementing IComparer<T> in a separate class, as the separate comparison. Just bear in mind that you'll still want to return 0 for Compare(x, x) for example, otherwise you'd never be able to find anything in the set other than by iterating over it...
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