How to reuse `readFile` `writeFile` program with this module trick?
Assuming `IO.readFile` and `IO.writeFile` is replaced by HTTP requests.
I can define `writeFile` and `readFile` in a type class and then implement the effect for HTTP variant, hiding the HTTP client beneath.
Is it just wiring it up in mixins, cabal file?
I think general conclusion is that there's no need for dependency injection, environment objects, or similar tricks if module system is rich enough.
For a long time I questioned why Python needs anything but `async def` or `def` (async should be achievable through module or `yield` usage) and `import` statements, to achieve maximal reuse, given dynamic nature of language and modules. We could ignore all object-oriented features, decorators, replace them with modules. Would be flatter and readable compared to bloated feature set.
And I wouldn't be surprised if there were more retired left handed surgeons in their 50s living in rural Switzerland than people who understand what he's talking about.
Indeed so, but that would require a few months worth of work from the reader, unfortunately.
(I have a t-shirt with a lambda in a circle, reminiscent of the anarchist emblem, and words "no class, no state". It's definitely possible to explain to a passer-by who never studied FP what it refers to, but not in such a way that the joke remained funny. Possibly the same deal is with the bumper sticker saying "my other car is cdr".)
"Humor can be dissected, as a frog can, but the thing dies in the process and the innards are discouraging to any but the pure scientific mind." - E. B. White.
The CS understanding of "No class, no state" is just about at the edge of something Aphex Twin might care about. But the stylized A really isn't that similar to a Lambda
In this case that’s the >>= from Maybe.Monad. As long as you satisfy the signature, it’s happy . do has nothing to do with Monads! Who lied to you?
Could have been a stronger point by using a non-monadic >>=.
I've been doing a lot of parsing lately and I find I don't need to reach all the way for monad (applicative is usually enough). But I guess that's what ApplicativeDo[1] is for.
We’ve got to be explicit now which Functor or Monad we’re importing, and you can’t have do notation for different Monads in the same module.
This is a bit rough for usability (not to mention also undermines the point above).
But overall I like the approach of trying something radically new.
ApplicativeDo can be thought of as a compile-time transformation that turns sequential code into possibly parallel* code just by analyzing the way variables are used. Once I've had that realization I really appreciated it more.
*: By "possibly parallel" I mean the blocks of code are known to be independent from each other. They could be actually executed in parallel if the Applicative instance does so.
The problem is that this is not only about Haskell's fundamentals. It's about them being extended with backpack, an extension that very few people use.
And honestly, I don't see the point there either. I know that backpack is meant to solve some problem everybody has, but I haven't been able to fully understand what that problem is. Specifically on this article, I don't see the gain over using a type class.
even for someone moderately interested in FP, this one goes above my head and the only take-away I can get from it is "maybe use ocaml instead of haskell"
It's more of an experiment: what if we take this beloved feature from OCaml to port it to Haskell (backpack), and see if it can replace a different beloved Haskell feature (type classes).
I'm reasonably versed in Haskell and my response would be that it shouldn't make that much difference to you what they've written in here. I've yet to see any code in the wild using the backpack extension.
> Have you ever seen a Number grazing in the fields? Or a Functor chirping in the trees? No? That’s because they’re LIES. LIES told by the bourgeoisie to keep common folk down.
Grumbling about how typeclasses could just be normal datatypes has been an undercurrent in the Haskell world for a long time, particularly as a way to solve the orphan instances problem. However, the syntactic grease provided by typeclasses is pretty appealing, and in the end I think this may have died down because people developed engineering solutions to the orphan instances problem (mostly "don't") that mitigated the theoretical problems enough that even most Haskellers don't care anymore... but I guess a few do still somewhat, because such things never truly go away.
(And yes, I recognize the quoted sentence as being humorous and labeling the entire article as not entirely serious... my point is that it is not entirely unserious either. The idea has been kicking around seriously for a while.)
There is a really interesting interview with Simon Peyton-Jones referenced on HN yesterday.He talks a lot about why Haskell came about, and some of the thinking behind the design choices that were made.
Assuming `IO.readFile` and `IO.writeFile` is replaced by HTTP requests. I can define `writeFile` and `readFile` in a type class and then implement the effect for HTTP variant, hiding the HTTP client beneath.
Is it just wiring it up in mixins, cabal file?
I think general conclusion is that there's no need for dependency injection, environment objects, or similar tricks if module system is rich enough.
For a long time I questioned why Python needs anything but `async def` or `def` (async should be achievable through module or `yield` usage) and `import` statements, to achieve maximal reuse, given dynamic nature of language and modules. We could ignore all object-oriented features, decorators, replace them with modules. Would be flatter and readable compared to bloated feature set.
And I wouldn't be surprised if there were more retired left handed surgeons in their 50s living in rural Switzerland than people who understand what he's talking about.
(I have a t-shirt with a lambda in a circle, reminiscent of the anarchist emblem, and words "no class, no state". It's definitely possible to explain to a passer-by who never studied FP what it refers to, but not in such a way that the joke remained funny. Possibly the same deal is with the bumper sticker saying "my other car is cdr".)
How often do people think you're a Half-Life fan instead?
I've been doing a lot of parsing lately and I find I don't need to reach all the way for monad (applicative is usually enough). But I guess that's what ApplicativeDo[1] is for.
This is a bit rough for usability (not to mention also undermines the point above).But overall I like the approach of trying something radically new.
[1] https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/appl...
*: By "possibly parallel" I mean the blocks of code are known to be independent from each other. They could be actually executed in parallel if the Applicative instance does so.
That era is now over.
And honestly, I don't see the point there either. I know that backpack is meant to solve some problem everybody has, but I haven't been able to fully understand what that problem is. Specifically on this article, I don't see the gain over using a type class.
> Have you ever seen a Number grazing in the fields? Or a Functor chirping in the trees? No? That’s because they’re LIES. LIES told by the bourgeoisie to keep common folk down.
(And yes, I recognize the quoted sentence as being humorous and labeling the entire article as not entirely serious... my point is that it is not entirely unserious either. The idea has been kicking around seriously for a while.)
https://news.ycombinator.com/item?id=45242530
https://williamcotton.com/articles/a-burrito-is-a-monad