https://issues.dlang.org/show_bug.cgi?id=14804
--- Comment #2 from monkeywork...@hotmail.com --- I agree opCmp is a little weird to implement for Nullable, but it's really not much different from NaN. If we follow what the floating point numbers do: Nullable!int n1; Nullable!int n2 = 0; assert(!(n1 < n2) && !(n1 == n2) && !(n1 > n2)); Of course the semantics of NaN are somewhat confusing at first and possibly bug-prone, so it may not be something we want to duplicate in another type if possible. Interestingly, this is how the built-in "nullable" types behave when compared: Object o1 = null; Object o2 = new Object(); assert(o1 > o2); //Segfault int* i1 = null; int* i2 = new int(0); assert(i1 <= i2); //One of these will pass assert(i1 > i2); int[] a1 = null; int[] a2 = [0]; assert(a1 <= a2); //I didn't know this was valid code; assert(a1 > a2); //it must compare the array pointers //and thus work similarly to case 2 So it looks like we have our choice of semantics to choose from. Either way, the issue of opCmp is completely separate from opEquals, so I don't agree that this bug should be closed. Every built-in nullable type in D works as I described, and I don't believe that Nullable should be any different. Object o1 = null; Object o2 = new Object(); assert(o1 != o2); //Passes int* i1 = null; int* i2 = new int(0); assert(i1 != i2); //Passes int[] a1 = null; int[] a2 = [0]; assert(a1 != a2); //Passes The fact that these issues pop up when you actually try to use Nullable in any serious way suggest to me that its design is deeply flawed, and that it should be deprecated and replaced at some point. However, until that happens, we should aim to improve it as much as possible without breaking existing code. If you don't want to open a defect for Nullable.opCmp, that's fine with me, but let's not close this one for opEquals. --