Scala performance: when you should betray your functional programming principles

*The 6 first minutes are missing, we apologise for it 🙏*

Functional programming is great! Immutability and an effects system make programs safer, better, stronger − but not always faster. Today, we’ll gleefully betray our functional principles, and look at how (and when!) you should consider committing such despicable acts as: - making your classes mutable and exposing their internals. - using while-loops instead of for-loops. - preferring arrays to lists or maps.

Of course, I’ll bring a few benchmarks to show the differences. And while we’re there, we’ll talk a bit about benchmarks, performance in general, and why the ‘Big O’ notation is lying to you.

[Jankoekepannekoek]

Project Valhalla should make it so the clean code will be as fast as the UGLY code.