add a simple NotNull struct #477
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| takesNotNull(notNull(test)); // test is null now, so this should throw an assert failure | ||
| assert(0, "it let us pass a null value to a NotNull function"); |
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Isn't this going to be caught by the catch clause as well? See assertThrown and friends.
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Oh, you're right! Duh. Changed to assertThrown!AssertError
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Shouldn't |
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I was thinking of the not null as being similar to a contract; it looks for usage errors in the program rather than something like user input, so assert is the thing. I think assert is right. |
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FWIW, I agree that we should use assert for this. |
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| /// A convenience function to construct a NotNull value. If you pass it null, it will throw. |
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Maybe an |
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How about adding an Also, this type does not work for all possible types T, thus it should have a template constraint. |
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I actually had the opAssign before, but removed it in tonight's commit. The reason is you might want the type system to catch an accidental assignment so you can make a decision - check null or assume null - at that time and write it explicitly. The same logic could apply to the constructor, but the fact that you can't use auto is annoying enough as it is, and having to do NotNull!T t = assumeNotNull(new T()); is probably just too far. |
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I agree, the transition from nullable to non-nullable should be explicit when possible, it just seemed a little out of sync with the constructor. I suppose construction isn't a problem because the name of the type, NotNull, will always be explicit at least once. |
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| /// A convenience function to construct a NotNull value from something you know isn't null. | ||
| NotNull!T assumeNotNull(T)(T t) |
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I think this function should contain an assert(t !is null)
| // have used a regular int*, but with the assurance that | ||
| // it never stored null. | ||
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| */ |
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This seems to be languishing. @adamdruppe, still there? |
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I've been very busy the last couple months with a lot of Going to be settling down again soon; moving this week On Sun, Jul 01, 2012 at 07:02:27PM -0700, Andrei Alexandrescu wrote:
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waiting |
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Will close this for now, please reopen as fit. Thanks! |
I've talked about implementing these a lot of times on the newsgroup, but I don't see one in Phobos yet!
This is my latest idea on how to implement a NotNull type with tests and documentation, added
to std.typecons (right below Nullable).
I haven't actually used any NotNull in practice, but from the attached tests, it looks like it will work well - hence, the pull request.
I'm open to any comments, however.