Exactly, for high correctness I like to use F#, which is also reasonably fast (almost C# speed, with a lot of ML goodies). For high correctness & high performa

Exactly, for high correctness I like to use F#, which is also reasonably fast (almost C# speed, with a lot of ML goodies). For high correctness & high performance I think Rust is a great choice, although some of the libraries aren't there yet in terms of maturity. So I usually only use Rust for programs with a small scope where I know that everything I need is available. Or make a DLL with a C interface that I can then call from F#.