haskell-awk VS polysemy

I use a smooth awk-like tool called hawk for similar reasons and it sure is nice, can recommend.

Looking for a few projects that make use of it, I found accelerate, hawk, polysemy and pretty-simple, so I'll be interested to poke around in their code and see how they have things set up.

For easy, rapid development. If I'm processing text at the command-line and I realize that I need a Unix command-line tool which doesn't yet exist, say, one which reverses each line, I can very easily pipe my text into ghc -e 'interact (unlines . reverse . lines)' (or even more easily as hawk -md L.reverse) and move on to the next step of my text manipulation. If I had to open a text editor, create a new Haskell project, write the code which grabs the input, processes the lines, and then outputs the result, then this amount of friction is large enough that it's not worth it for a one time task. I'd probably find a different way to do it which is less expedient than the interact solution but more expedient than creating a new Haskell project.

hint maintainer here! To use dependencies, you need to use unsafeRunInterpreterWithArgs to pass extra -package-db arguments to ghc. In my hawk project, I'm trying hard to use the same package database in which hawk itself was installed, so I wrote a bunch of code to detect which installation method was used and to figure out the package database folder from there.

Thirdly, composing arbitrary effects without losing state is really, really difficult. Things are fine when you limit yourself to State and Reader, sure, but once you start with nondeterminism you’ll discover it’s shockingly easy to produce behaviors that are baffling unless you’ve spent a preposterous amount of time thinking about this stuff. (I’ve been bitten in prod by silent state-dropping bugs, and rarely have I been more flummoxed.) Consider this example, which produces silent changes in the semantics of <|> depending on whether you use it inside or outside of a higher-order effect. Every single effect library (besides the still-unreleased eff) gets certain combinations of effects + nondeterminism wrong. You could make the argument that most people don’t use nondeterministic monads, but eDSLs really shine when you have access to them, as you can turn a concrete interpreter to an abstract one fairly easily.

Looking for a few projects that make use of it, I found accelerate, hawk, polysemy and pretty-simple, so I'll be interested to poke around in their code and see how they have things set up.

Right, I think I'll just give it a shot to see. Polysemy is nice but I'm still having trouble getting what I want out of it (which may very well be entirely a fault of my own understanding)

Languages such as Koka only support algebraic effects, not scoping operations such as catch and listen. The Effect Handlers in Scope paper introduces scoping operations, which lead to the Haskell libraries fused-effects and polysemy, but they turned out to have some weird semantics. eff is her effort to fix that.

Looking at the interpreter for Reader might give some clues if this doesn't work. https://github.com/polysemy-research/polysemy/blob/master/src/Polysemy/Reader.hs#L38-L45

*But I'm not terribly well versed in Scala's other DI offerings. I came from Haskell and didn't find anything in Scala that clicked with me until I found ZIO. It reminded me a lot of my favorite way of writing Haskell programs (https://github.com/polysemy-research/polysemy)—albeit with a completely different implementation.