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Comment by garrinm | Hacker News Reader

This gets discussed in the Roc community. They are exploring designing a language without higher kinded polymorphism.

Here's a snippet from the Roc FAQ.

> It's impossible for a programming language to be neutral on this. If the language doesn't support HKP, nobody can implement a Monad typeclass (or equivalent) in any way that can be expected to catch on. Advocacy to add HKP to the language will inevitably follow. If the language does support HKP, one or more alternate standard libraries built around monads will inevitably follow, along with corresponding cultural changes. (See Scala for example.) Culturally, to support HKP is to take a side, and to decline to support it is also to take a side.

https://www.roc-lang.org/faq.html#higher-kinded-polymorphism

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I feel like adding HKP isn't "taking a side" nearly as much as not adding HKP to turn people away because you don't like their cultural contribution.

By adding the feature you aren't actually excluding the people who don't want to use it. They are free to avoid it and maintain parallel ecosystems where HKP is avoided.

You are only excluding them if the standard library forces them to interact with HKP code, which arguably Haskell does, and it makes a PITA for teaching it. Haskell however isn't doing it with the intention of exclusion.

On the other hand, not adding the feature because you don't like the culture it brings is intentionally exclusionary. You're intentionally taking a side against certain kinds of people and the certain kinds of code they want to be able to express without repetition... and you're hamstringing the expressibility of your language to do it.

I completely understand wanting to avoid HKP for teaching purposes, but maybe that is a problem that could better be resolved by always providing monomorphic options for standard library functions....

But avoiding HKP to avoid a certain kind of culture? Well now it's personal!

As the FAQ entry notes, one of the "sides" in the design space here is "a fragmented ecosystem is best because there's no other way to accommodate the variety of different styles people want to use" - this is a totally reasonable preference to have!

Still, hopefully it's clear why a language designer might want to go down a different path. After all, it's also totally reasonable to prefer an ecosystem which isn't fragmented along these lines (the way it is in, say, Scala) even though it means fewer different programming styles are supported.

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