Seems like a Clang thing for C++17 and up (which is what Codewars uses). On Compiler Explorer, both GCC and MSVC compile without issue (and Clang C++14 ironically). For whatever reason, Clang seems unable to see the size of your array at compile time(?) No idea why that is. But if you are explicit with it, that should solve it.

I agree.

tribonacci

I'm working fine in VS but it's wrong here, is it my problem?

In file included from main.cpp:7:
./tests.cpp:6:23: error: static_assert expression is not an integral constant expression
        static_assert(Hi::value[0] == 'H' && Hi::value[1] == 'i' && Hi::value[2] == '\0', "");
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./tests.cpp:6:23: note: read of pointer to element of array without known bound is not allowed in a constant expression
1 error generated.

what's this kata want to ask me?

I believe this Kate deserves a higher rank. It took me approximately an hour to engage in mathematical reasoning and resolve precision-related matters.

There will be 'RVO'.

perhaps you can use signature.cbegin()

So how should it pronouce in Italian?

what's this??

cute

WTF

Woah! I just found out you can use boost here！