Haskell Gotchas

A book called The Haskell School of Music has this on page 4:

5 ∗ (−0.123456 + 0.123457) :: Float ⇒ 4.991889e − 6
5 ∗ (−0.123456) + 5 ∗ (0.123457) :: Float ⇒ 5.00679e − 6

Floating point rounding errors aren’t unique to Haskell of course, but I still think it’s curious with a sample of how it can go wrong.

Another “gotcha” is Haskell’s default string: they’re (still) linked lists. And you wouldn’t think much of it, until you see the performance. My most efficient optimization for my master’s thesis (which I’ve partially kept on my github profile) was converting input reading to be Data.Text instead of default strings. For large inputs it made a big difference. If you take a gander at the code you’ll also notice that it’s heavy with strict evaluation - as opposed to Haskell’s lazy-by-default design. Generally, when benchmarking I found this to be more efficient and also predictable if I was debugging something else.

Beyond that I’d like to say I love writing Haskell, albeit I devote less time for it now than before. Though, with the advent of AI, I find that it is getting easier. Give it a whirl!