[fabriceleal]

Probably more about the difference between "echo" and "std::cout << ... << std::endl;" than the recursive function call.

[Sean1708]

I would be very very surprised if printing "2971215073" accounted for more than 1 second of runtime.

[gambler]

Well, I know that printing stuff to console can be ridiculously slow, so this doesn't surprise me much.

[Sean1708]

An entire second to print 10 characters?! How does a terminal that slow even exist?

[VeXocide]

std::endl flushes which isn't cheap, you're generally better off simply steaming in a newline.

[lucozade]

Most of it won't be because the C++ constexpr version has the same IO call and runs in <0.1s.

[syockit]

I think that's because even the std::cout call could be precalculated, so no runtime string concatenation and stream magic is involved.