I recently wrote a small source code counter and as part of the process I naturally ran some benchmarks to compare to the many tools that already exist. The results were somewhat erratic, but I was quite disappointed with Rust.

Results on the Rust repo:

Tool Language Time
polyglot ATS 218.3 ms
loc Rust 139.5 ms
tokei Rust 333.3 ms
enry Go 5.183 s
cloc Perl 16.47 s
linguist Ruby 16.70 s


Functional paradigms really shine here. Streams in ATS are just plain easier than in Rust (which, given the state of ATS documentation, says more about Rust than me). The polyglot example is even compiled with a garbage collector, which puts just how slow Rust is into perspective.

The usual response to this is "you can write slow code in any language". Which is of course not the point - Haskell is far more expressive, easier to refactor, and has more safety guarantees. When you remove speed as a consideration, Rust starts looking a lot less attractive.

Moreover, functional programming in general is vindicated - abstraction is an underrated tool for performance, and here we see just how much we are missing out on in Rust. tokei takes longer on four cores that poly on one, even using rayon and the Rust ecosystem! Not only is "functional programming is slow" false, in fact the opposite is true! I suspect we will see much more use of formal verification and linear types in performant code as we go forward.