feat(c++): Use C++17's nested namespaces

[acezen]

Describe the enhancement requested

Clang-tidy prefers it. It is more compact and now that we are on C++ 17 I don't see any reason we shouldn't move everything over.

Before:

namespace graphar {
namespace util {

After:

namespace graphar::util {

Component(s)

C++

[ywh555hhh]

Hello, I'm interested in taking on this issue. I understand it involves implementing cleaner code. Could you please assign it to me? Thank you.

[lixueclaire]

Hello, I'm interested in taking on this issue. I understand it involves implementing cleaner code. Could you please assign it to me? Thank you.

Sure, the issue has been assigned to you. Thank you for your interest, and we are looking forward to your contribution.

[ywh555hhh]

Hello, I have a question. In the case where we have code in the graphar namespace but not in any nested namespace (like the Status class functions), should we still modify the namespace to use the C++17 nested namespace syntax? From my understanding, using the new syntax wouldn't reduce the nesting in this case. Could you please clarify this? Thank you.

here

[lixueclaire]

Hello, I have a question. In the case where we have code in the graphar namespace but not in any nested namespace (like the Status class functions), should we still modify the namespace to use the C++17 nested namespace syntax? From my understanding, using the new syntax wouldn't reduce the nesting in this case. Could you please clarify this? Thank you.

here

Hi, I think you could separate the code and re-org them using the new style, like:

namespace graphar::util {
...
}

namespace graphar {
...
}

[ywh555hhh]

Can this issue be closed?

[acezen]

yes, thanks for @ywh555hhh 's work, the issue has been resolved.