You're describing a performance optimization. Yes, if you write unoptimized code, it often takes some refactoring to support the optimization. Also, Python and

You're describing a performance optimization. Yes, if you write unoptimized code, it often takes some refactoring to support the optimization. Also, Python and Ruby are proof that languages can be tremendously successful at solving a huge array of problems without shared memory parallelism in v1.0. Besides, Crystal is presumably much faster than either of these languages with a single thread, so the relative advantage of (CPU) parallelization is much less.