On Sunday, 19 May 2013 at 01:20:31 UTC, Walter Bright wrote:
I understand that. But the rationale you gave for having a default constructor was to be able to disable default construction.
RAII or construction based on template parameters.
I know that some languages have a special syntax for non-null pointers. I disliked this solution for D because non-nullable pointers are just one instance of creating a type with a limited set of values. Why not go for a general solution? Why not create a mechanism where a type can be defined that can only consist of prime numbers, for example? Why not ranged integer types?
Actually most languages does the reverse. They have non nullable type, and provide Nullable/Option/Maybe/whatever to allow for nullable type. It allow to ensure that null don't pops up in unexpected places, and that null must be handled when it is an option.
The current solution is to rely on faith, and I remember someone talking about that at DConf recently.
Now that what other languages does is cleared, let's do some consideration on null.
A pointer point on something. For instance, an int* point on an integer. null doesn't point on a integer. Non nullable pointer aren't a restricted set of values, as, by definition, null isn't a value that point to an int. That doesn't stand either.
D already have thing like Nullable in the standard lib. Introducing Maybe is also pretty easy. Adding NonNullable in addition to Nullable sound like something is not quite right.
The benefit we get from null, ie having a default initialization for everything, is moot if @disable this() is introduced, so it is questionable at this point how useful it really is except as make up over current implementation deficiencies.
Finally it has to be added that null cause holes in @safe in ways that are difficult to impossible to solve.
