How close can pure functional programming get to C?

How close can pure FP get to C? October 22, 2026 In Why Lean is Faster Than Rust, the author shares an impressive result: a DEFLATE compression library written in Lean 4, a functional programming language and proof assistant, outperforming an equivalent Rust package that crates.io says has been downloaded over a billion times. From the article: lean-zip beats every single compression level miniz_oxide provides, i.e. we're capable of providing the same compression at higher throughput. At its fas