modern C++: initialise a static array inside a class

RE: modern C++: initialise a static array inside a class

Jan Cumps — Sun, 12 Apr 2026 15:36:50 GMT

I'm making a few changes to the nmea lib API and code: let the library return objects, instead of passing them via output parameters

Since C++17, the compiler can directly use the object that receives the return value. So no constructors or copies are called in this mechanism.

Old version:

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:d86aa9d4-9b58-4308-b469-fdadf446b1db:type=csharp&text=void%20nmea%3A%3Atime%28const%20std%3A%3Astring_view%26%20sv%2C%20time_t%26%20t%29%20%7B%0A%09std%3A%3Astring%20s%28sv%29%3B%0A%09t%20%3D%20time_t%7B%0A%09%09std%3A%3Achrono%3A%3Ahours%28std%3A%3Astoi%28s.substr%280%2C%20%202%29%29%29%20%2B%0A%09%09std%3A%3Achrono%3A%3Aminutes%28std%3A%3Astoi%28s.substr%282%2C%20%202%29%29%29%20%2B%0A%09%20%20%20%20std%3A%3Achrono%3A%3Aseconds%28std%3A%3Astoi%28s.substr%284%2C%20%202%29%29%29%20%2B%0A%09%09std%3A%3Achrono%3A%3Amilliseconds%28std%3A%3Astoi%28s.substr%287%29%29%29%0A%09%7D%3B%0A%7D]

New version (uses exactly same amount of resources):

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:4acad8b4-446b-4766-9618-1b9a66d3f265:type=csharp&text=time_t%20nmea%3A%3Atime%28const%20std%3A%3Astring_view%26%20sv%29%20%7B%0A%09std%3A%3Astring%20s%28sv%29%3B%0A%09return%20time_t%7B%0A%09%09std%3A%3Achrono%3A%3Ahours%28std%3A%3Astoi%28s.substr%280%2C%20%202%29%29%29%20%2B%0A%09%09std%3A%3Achrono%3A%3Aminutes%28std%3A%3Astoi%28s.substr%282%2C%20%202%29%29%29%20%2B%0A%09%20%20%20%20std%3A%3Achrono%3A%3Aseconds%28std%3A%3Astoi%28s.substr%284%2C%20%202%29%29%29%20%2B%0A%09%09std%3A%3Achrono%3A%3Amilliseconds%28std%3A%3Astoi%28s.substr%287%29%29%29%0A%09%7D%3B%0A%7D]

All API functions that use an output parameter have been adapted. I'm running tests to see if any regression happened...

RE: modern C++: initialise a static array inside a class

DAB — Fri, 28 Nov 2025 19:53:14 GMT

Nice update Jan.

RE: modern C++: initialise a static array inside a class

vmate — Mon, 24 Nov 2025 21:06:51 GMT

A notable exception is that with constexpr arrays, this can be done pre-c++17:
[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:47de98d5-fed6-4b84-9725-142ddc6d2327:type=c_cpp&text=class%20myclass%20%7B%0Apublic%3A%0A%20%20%20%20static%20constexpr%20uint32_t%20myarray%5B4%5D%20%3D%20%7B1%2C%202%2C%203%2C%204%7D%3B%0A%7D%3B]

Also, in recent versions of C++, std::array should probably be used instead of 'regular' arrays:
[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:b0b6e540-4942-478a-99eb-9bcccb49e685:type=c_cpp&text=class%20myclass%20%7B%0Aprivate%3A%0A%20%20%20%20inline%20static%20std%3A%3Aarray%3Cuint32_t%2C%204%3E%20myarray%20%3D%20%7B0%7D%3B%0A%7D]
Instead of myarray becoming a uint32_t pointer, and then the programmer is responsible for doing everything correctly with it, std::array actually behaves as a proper object, it knows its own size, can be assigned properly to another array, etc. It has a bunch of convenience features like .begin() and .end() too, and it is zero cost.