Is there a reason for most members of std::bitset not to be constexpr? For example bitset.none(), all(), any(),count().

Currently this simple program fails to compile.

#include<bitset>


int main()

{

constexpr std::bitset<20> bits{};

constexpr auto is_none = bits.none(); //Fails as none() isn’t constexpr

}


Thanks in advance,  
Henrik