This kind of procedural array-based numerical code, would be easier to rewrite in Fortran than in Rust. Fortran syntax is closer to the original Python syntax,

This kind of procedural array-based numerical code, would be easier to rewrite in Fortran than in Rust. Fortran syntax is closer to the original Python syntax, than Rust is. And Fortran is easier to learn than Rust. But the author already knows Rust, so.