4 ms·

Namespaces are often called for especially by programmers used to C++ but doing C. They seem like such a simple feature to implement. I'm still not sure I like

Namespaces are often called for especially by programmers used to C++ but doing C. They seem like such a simple feature to implement. I'm still not sure I like them: - What is the benefit of using A::B::C versus A_B_C, really, in terms of avoiding name clashes? I can point out one immediate benefit of doing the latter - code is easier to read because line noise is reduced (perhaps subjective but I think it will be hard arguing the other way around). - Is it a good thing that half the code will now refer to A::B::C using only B::C or even only C? Without assistance of a program with good semantic insight (a solid IDE, etc) this only makes identifier search harder. - Namespaces "enforce" discipline in one way - you can be sure that the symbols at the binary level will be properly prefixed. But with only a little discipline programmers can do the prefixing themselves, and in return they can move code between files (/namespaces) more freely, which is good for refactoring. And as a sibling commenter pointed out, one factor why namespaces get called for could be lack of understanding that we can hide the "guts" of any function (or variable) using "static" linkage. There is less discipline (prefixes..) needed for these functions because they are only visible in the current translation unit.

pjmlp 4y ago
Namespaces can be assigned alias to avoid colisions, good luck doing that to A_B_C.
- jstimpfle 4y ago
  Good point, but then again I'm not that sure it's a net benefit because I like everything in a codebase to refer to a given object using the exact same name. I suppose aliasing is useful for widely used libraries, for example if a big software projects wants to include two different versions of the same library. Or Team A wants to rename their module but make it easier for other teams that use their module to follow suit. All that can provide some ease of use in the short term but produces more mess to clean up in the long term. IMHO. Real name clashes between two different libraries are quite unlikely, and namespaces would only solve that problem on the source code level, not on the binary / symbol level.
selfmodruntime 4y ago
Namespaces can enforce good project structure. If you're using A::B::C and A::B::D you can be 100% that both C and D definitely live under B, and your editor can work with that as well.
- jstimpfle 4y ago
  > you can be 100% that both C and D definitely live under B And that brings you what benefit exactly? I've seen a number of projects that are preoccupied about "proper nesting", while it is 99% bureaucratics and all those projects are still a mess. The benefits of "living under this or that" are technically zero, and with respect to human factors are minimal given that 1) you can get most of the organizational benefits of namespaces by doing A_B_C, and 2) you can also add new members to proper namespaces from external files in most languages, including C++, so there really isn't a difference w.r.t "knowing for sure".
  - selfmodruntime 4y ago
    The benefit is a nice mental model of where what function lives (if you don‘t overdo it). This type of packaging also lends itself to module systems, a thing I desperately wish for in C
    - jstimpfle 4y ago
      This type of "packaging" is completely orthogonal to module systems. It's merely a syntactic discipline that adds one more complication to deal with even where it has zero benefit. You could say that the C/C++ systems already has "modules" if you look at object files and header files. Of course, they are a limited kind of modules because they are a bit low-level and C has the preprocessor problem, making it slow to "import" modules. But none of that has to do with namespaces.
- astrange 4y ago
  Well, they enforce having a lot of project structure. Java and C# use their namespaces to ensure that everything useful is under five layers of pointless names like System.Collections.com.net.org.ArrayList. I think not having namespaces may be an effective way to prevent enterprise programming from happening.
lifthrasiir 4y ago
> What is the benefit of using A::B::C versus A_B_C, really, in terms of avoiding name clashes? Many C programs do not use hierarchical names like `A_B_C` as they ideally should. They instead pick a short identifier that is (often incorrectly) believed to be distinct enough. > Is it a good thing that half the code will now refer to A::B::C using only B::C or even only C? Without assistance of a program with good semantic insight (a solid IDE, etc) this only makes identifier search harder. If you meant that the identifier search should be possible with just grep, yeah namespace makes it harder but it's not the only cause and this doesn't explain why many other languages with less overall IDE support than C/C++ have namespaces. And I believe it is possible to design a namespace system that only needs a ctags-level automation for proper identifier search, though I don't know how you feel about ctags.
- jstimpfle 4y ago
  > Many C programs do not use hierarchical names like `A_B_C` as they ideally should. They instead pick a short identifier that is (often incorrectly) believed to be distinct enough. What is your list of name clashes that you experienced? How many real headaches did they give you? Or is it all a non-problem? Not a rhetorical question - I'm mostly working on smaller projects < 100KLOC. > I don't know how you feel about ctags. I use ctags from time to time when I have to, but I still don't like it when there are multiple namespaces that contain the same set of names which confuses navigation operations, even vim with ctags I think. Maybe even IDEs like Visual Studio, I'd have to check though what works and what doesn't.
  - lifthrasiir 4y ago
    > What is your list of name clashes that you experienced? How much real headaches did they give you? Or is it all a non-problem? Not a rhetorical question - I'm mostly working on smaller projects < 100KLOC. I too refrained from using C for that large software so I don't have many examples either, but in one case I was using TweetNaCl where you have to supply `extern void randombytes(unsigned char*, unsigned long long)` for CSPRNG and I had to rename it for some reason I can no longer recall.
  - 4y ago

pjmlp 4y ago

Namespaces can be assigned alias to avoid colisions, good luck doing that to A_B_C.

jstimpfle 4y ago
Good point, but then again I'm not that sure it's a net benefit because I like everything in a codebase to refer to a given object using the exact same name. I suppose aliasing is useful for widely used libraries, for example if a big software projects wants to include two different versions of the same library. Or Team A wants to rename their module but make it easier for other teams that use their module to follow suit. All that can provide some ease of use in the short term but produces more mess to clean up in the long term. IMHO. Real name clashes between two different libraries are quite unlikely, and namespaces would only solve that problem on the source code level, not on the binary / symbol level.

selfmodruntime 4y ago

Namespaces can enforce good project structure. If you're using A::B::C and A::B::D you can be 100% that both C and D definitely live under B, and your editor can work with that as well.

jstimpfle 4y ago
> you can be 100% that both C and D definitely live under B And that brings you what benefit exactly? I've seen a number of projects that are preoccupied about "proper nesting", while it is 99% bureaucratics and all those projects are still a mess. The benefits of "living under this or that" are technically zero, and with respect to human factors are minimal given that 1) you can get most of the organizational benefits of namespaces by doing A_B_C, and 2) you can also add new members to proper namespaces from external files in most languages, including C++, so there really isn't a difference w.r.t "knowing for sure".
- selfmodruntime 4y ago
  The benefit is a nice mental model of where what function lives (if you don‘t overdo it). This type of packaging also lends itself to module systems, a thing I desperately wish for in C
  - jstimpfle 4y ago
    This type of "packaging" is completely orthogonal to module systems. It's merely a syntactic discipline that adds one more complication to deal with even where it has zero benefit. You could say that the C/C++ systems already has "modules" if you look at object files and header files. Of course, they are a limited kind of modules because they are a bit low-level and C has the preprocessor problem, making it slow to "import" modules. But none of that has to do with namespaces.
astrange 4y ago
Well, they enforce having a lot of project structure. Java and C# use their namespaces to ensure that everything useful is under five layers of pointless names like System.Collections.com.net.org.ArrayList. I think not having namespaces may be an effective way to prevent enterprise programming from happening.

lifthrasiir 4y ago

> What is the benefit of using A::B::C versus A_B_C, really, in terms of avoiding name clashes? Many C programs do not use hierarchical names like `A_B_C` as they ideally should. They instead pick a short identifier that is (often incorrectly) believed to be distinct enough. > Is it a good thing that half the code will now refer to A::B::C using only B::C or even only C? Without assistance of a program with good semantic insight (a solid IDE, etc) this only makes identifier search harder. If you meant that the identifier search should be possible with just grep, yeah namespace makes it harder but it's not the only cause and this doesn't explain why many other languages with less overall IDE support than C/C++ have namespaces. And I believe it is possible to design a namespace system that only needs a ctags-level automation for proper identifier search, though I don't know how you feel about ctags.

jstimpfle 4y ago
> Many C programs do not use hierarchical names like `A_B_C` as they ideally should. They instead pick a short identifier that is (often incorrectly) believed to be distinct enough. What is your list of name clashes that you experienced? How many real headaches did they give you? Or is it all a non-problem? Not a rhetorical question - I'm mostly working on smaller projects < 100KLOC. > I don't know how you feel about ctags. I use ctags from time to time when I have to, but I still don't like it when there are multiple namespaces that contain the same set of names which confuses navigation operations, even vim with ctags I think. Maybe even IDEs like Visual Studio, I'd have to check though what works and what doesn't.
- lifthrasiir 4y ago
  > What is your list of name clashes that you experienced? How much real headaches did they give you? Or is it all a non-problem? Not a rhetorical question - I'm mostly working on smaller projects < 100KLOC. I too refrained from using C for that large software so I don't have many examples either, but in one case I was using TweetNaCl where you have to supply `extern void randombytes(unsigned char*, unsigned long long)` for CSPRNG and I had to rename it for some reason I can no longer recall.
- 4y ago