"I'm assuming the example is supposed to look like this instead"
Well, that either won't work (it would load the same "library3" in both cases), or it would work with a sufficiently smart lookup algorithm.
Basically, when importing a file, I think it should look for it in this order: the cwd, the folder (and subfolders) where the importee is defined, then lastly the folder where Nulan itself is defined.
In that case, assuming library1 and library2 are in different folders and have different versions of library3 in their path, it would work.
This implies bundling the libraries you use with your app, which you pretty much have to do anyways.
In that case, this has nothing to do with name resolution, it has to do with file resolution: finding which file to import when given a name.
You could argue that's a good case for a package manager like RubyGem, and that may be true, but I consider such a system to be in a layer above the namespace system.
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"This challenge is a case where the library developers are trying to change their code without causing disruption for anyone else."
And Nulan's namespace system handles that just fine.
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"I think the point is that the library has been upgraded, and the library developer would like the upgrade to propagate to all code that uses the library, even though a few library users might actually prefer otherwise. This is a conflict of preferences, and the language might give tools to certain participants to "reconcile" this conflict."
I still don't get the impression they were talking about some sort of package management or version dependency resolution system. It's certainly okay to discuss such things, but I think they're outside the scope of a namespace system. That thread (and post) seemed to me to be talking specifically about resolving naming conflicts.
I think the talk about "multiple libraries" and "multiple versions" was just to create a situation where naming conflicts occur. I don't think it was meant to imply that the goal is to be able to easily change library versions on the fly, like you were discussing.
If I wanted some sort of system like that in Nulan, it wouldn't be particularly hard to do... you'd create a new file, like say... "dependencies.nu" and you'd then put a bunch of imports into it:
(import foo)
(import bar)
(import qux)
That's all it would be: a list of imports. Then all the dependencies are in one place, rather than scattered around in various files. I personally don't see much benefit to that, but you could do it if you wanted to.
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"However, I think Casey McCann is assuming a namespace system built on implicit name prefixes, which may or may not incorporate a way to take a name prefix and find a module that addresses it."
That is quite possible.
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"By "nothing at all," do you mean a late-bound global scope like Arc's?"
Yes. And JavaScript. Basically any language with dynamic scope at the global level by default.
Me: "This challenge is a case where the library developers are trying to change their code without causing disruption for anyone else."
You: "And Nulan's namespace system handles that just fine."
What I meant was that the library developer wants our applications to use their new library version without any involvement of the application developers. I seriously doubt that's what you're claiming to support.
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"You could argue that's a good case for a package manager like RubyGem, and that may be true, but I consider such a system to be in a layer above the namespace system."
I think the only place we really disagree now is that you're content to neglect the "RubyGem" parts of these challenges for the purposes this discussion, while I consider them the hardest parts. I think if you do try to design a package manager, you may very well get most of a namespace system out of the deal, or even a whole programming language.
Unfortunately, package managers and filesystems aren't quite a full layer above the languages they're used with. Program units tend to link together using hardcoded filenames or package names, a practice that ties some of the filesystem or package manager complexity into the complexity of the language proper.
The module system I've been working on recently (ever since [1]) is meant to help resolve that, by making the non-language-specific complexity as simple and universal as possible. It's based on two notions: A program is a multiset of independently maintained extensions, and it exists in the context of an expansive historical record containing all knowledge ever discovered (or at least all knowledge we have on hand).
The extensions and units of background knowledge may ultimately be encoded as files and managed at a "layer above" using traditional package managers and filesystems. However, they may also be manipulated as first-class values in a host program, or even as visual elements in a UI.
"In that case, this has nothing to do with name resolution, it has to do with file resolution: finding which file to import when given a name."
As an argument in favor of this viewpoint, I'll quote the original challenge:
"Now I'm writing a piece of code that uses two libraries, each of which use different, incompatible versions of some third library, causing namespace collisions between the two versions. How does the namespace system handle this?"
The challenge seems to imply that the two incompatible libraries were loaded successfully: it's NOT talking about file resolution. It's assuming the file resolution proceeded successfully, and thus the only issue remaining is resolving the name collisions.
You keep talking about things like dependency resolution systems, swapping in different libraries, etc. That's fine, but that does not seem to be what the challenges are talking about. I'd rather see some challenges specifically geared toward dependency resolution and file loading rather than trying to hijack namespace challenges, since I see these two issues as being orthogonal, with maybe a little overlap.
"The challenge seems to imply that the two incompatible libraries were loaded successfully: it's NOT talking about file resolution. It's assuming the file resolution proceeded successfully, and thus the only issue remaining is resolving the name collisions."
From what you quoted, technically that could be true.
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"You keep talking about things like dependency resolution systems, swapping in different libraries, etc. That's fine, but that does not seem to be what the challenges are talking about."
Objection! :)
The challenge we're talking about puts the words "different, incompatible versions" in italics. If direct substitution were unimportant, the challenge would not even need to use the word "version"; it could just say there were two separate libraries with name collisions. And yet that's precisely the scenario of the previous challenge.
"What I meant was that the library developer wants our applications to use their new library version without any involvement of the application developers. I seriously doubt that's what you're claiming to support."
I don't get the impression they're saying, "we release this new library and all the users of the existing libraries automatically switch to it". I think what they're saying is, "this library can be used by existing applications, but they still need to choose to use it". That's how I interpreted the "drop-in replacement" phrase.
Technically speaking Nulan can support that... you would change library1 and library2 to just import library3:
Then the applications don't need to change at all. That's assuming of course that the developers of library3 can change library1 and library2. If they can't, then oh well, my solution is for the applications to manually update to use library3 if they so wish. In that semi-contrived example it doesn't matter because library3 is a superset of library1 and library2, so applications can just keep using library1/2 just fine.
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"I think the only place we really disagree now is that you're content to neglect the "RubyGem" parts of these challenges for the purposes this discussion, while I consider them the hardest parts. I think if you do try to design a package manager, you may very well get most of a namespace system out of the deal, or even a whole programming language."
They are the hardest parts, I just don't think it has to do with namespace support, which that entire topic was devoted to. Nor am I particularly interested in designing a package manager.
So my suggestion still stands: if you feel this strongly about package managers, make up your own semi-contrived challenges that try to demonstrate what a package manager should be capable of doing. I'm sure it will include all kinds of stuff that was left out of the namespace challenges, because package managers are much more complex and involved than namespaces.
Then you can point to those challenges and I can say, "Nulan doesn't support that stuff" rather than trying to insist that Nulan is failing the namespace challenges because you're interpreting them far larger than what they actually said. I think it's useful to have "package manager challenges", but I think it's also useful to have "namespace challenges". I don't see why we need to throw out the namespace challenges just because you view it as "not as hard" as package managers.
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"The challenge we're talking about puts the words "different, incompatible versions" in italics. If direct substitution were unimportant, the challenge would not even need to use the word "version"; it could just say there were two separate libraries with name collisions. And yet that's precisely the scenario of the previous challenge."
Like I said, I don't get the impression they're talking about package managers. I think they used the phrase "different incompatible versions" because that's a situation that can actually occur in real life. They're using it as an example, that's all.
It's obvious that you want to think in terms of package managers, and that's fine, but I really do not get the impression that's what they're talking about. Ultimately, it seems the only way to resolve this is to actually ask them what they meant.
Oh, I can understand that point of view. Just because there were multiple examples doesn't mean each one introduced new requirements.
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"It's obvious that you want to think in terms of package managers, and that's fine, but I really do not get the impression that's what they're talking about."
I just wanted to help you elaborate on the claims you're making about Nulan's namespace system. You originally quoted Casey McCann's examples, but I perceived them differently than you did, and I had trouble understanding your perception from your terse example code.
Now this seems to be resolved. We may not agree in our interpretations, but now I understand your claims relative to both of them. Thanks for your patience with me. ^_^
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"Ultimately, it seems the only way to resolve this is to actually ask them what they meant."
I don't think that's necessary, but it would be interesting to know.
