Very honest discussion of the results. I liked it.
Would it be possible to use Futhark to rewrite the APL implementation instead of the Haskell one? That would make an interesting comparison.
Would it be possible to use Futhark to rewrite the APL implementation instead of the Haskell one? That would make an interesting comparison.
Sadly, from what I can see, the APL version makes use of so-called nested arrays in the 'words' function, specifically arrays of strings (this is different from multidimensional arrays). Futhark does not directly support nested arrays. A rewrite of the APL implementation would require using a quite different algorithm (or a nontrivial encoding).
But my APL is a bit rusty, so I may be wrong.
My first attempt did some stuff with subtracting items in an array from their neighbor. Now with info I got from [mlochbaum](https://news.ycombinator.com/user?id=mlochbaum) I have another version that uses windowed reductions.
So those are three versions there; after that I just split it up just to see where that leads and that actually ends up feeling a lot like the Haskell / Futhark solution to me.