Yes that's right, Dave. Coincidentally the sieve technique came up here only three weeks ago when a poster was trying to check a conjecture about Recaman's sequence. In thinking about primes, I did consider XS and C++ funnily enough, until I realised that prime or not is conceptually boolean and can be packed down to bits, so XS and C++ might be less urgent. Nevertheless I totally applaud the work you've done and XS and C++ is a very good choice.