#PureScript is almost the perfect #Haskell replacement. Not only for the things it brings to the table, but also for the things it does *not*.
I mean actual *features* missing from PureScript and not gotchas like *no historical baggage*!
Some examples below. All of them are good for simplicity and newbie friendliness!
1. No laziness.
Laziness makes it harder to reason about performance. There are easy workarounds for most common usecases for laziness, and employing clever laziness tricks is usually not worth the cost of complicating the codebase.
Also, you can approximate thunks with functions when needed. Typeclass trickery even allows call-by-name evaluation (see https://github.com/natefaubion/purescript-call-by-name).
2. Manual recursion is discouraged.
PureScript's TCO only works in special cases. Normally you wouldn't even need to deal with this because existing implementations of functions like map, foldr etc. are already tail recursion safe. For the rare cases when you need to manually recurse, you can use `tailRec` and `tailRecM` to ensure stack safety.
3. No special syntax or support for linked lists. Strings are not simply lists of chars.
This could potentially be put in the "no historical baggage" category. But I feel that a lot of people, especially newbies, view the special treatment of lists and strings as a plus for Haskell.
However, the focus on lists causes massive confusion for newbies when they are encouraged to use types like Vector and Text in production instead. The special inbuilt syntax also is an active impediment for learning (for example, how do you refer to the higher kinded List type when deriving an instance? It's a mental leap to get to `[]` in `instance Foo [] where`).
4. No special syntax for Tuples.
Much of what was said for lists also applies to tuples. The special syntax is confusing to newbies and causes code complications. For example, each length of tuple is a separate type, and typeclasses in Haskell need to derive instances for each separately. They usually derive instances for tuples only up to length 7.
In addition, it's rarely needed. I am yet to find a usecase for tuples where PureScript's wonderful support for records doesn't suffice. I thought one such usecase was case matching on multiple values (`case (v1, v2) of ...`), but PureScript supports multi case match for this exact usecase and avoids unnecessary boxing (In PureScript you would write `case v1, v2 of ...`).
@haskman
Strict-by-default is just asking users do to what a compiler should do.
For the same reason we don’t want to use manual memory management (even with the borrow checker assistance) all the time.
Let me focus on what’s important and let the compiler find a best way to do it.
@haskman what do you mean by complexity here?
@dpwiz Code complexity. Code that exploits laziness is harder to understand and reason about.
@haskman I find the opposite is true. Is that complexity or difficulty an objective thing?
@dpwiz I don't know if your question is rhetorical.
@haskman Either your claim about “laziness (by default) is bad” is objective/universal and one of is wrong (and I, personally, would like to stop being wrong). Or it is subjective and there’s nothing for us to argue about.
@haskman @dpwiz there is already a counterexample I provided: streams. In general, any structures you traverse from inside out are easier to write and understand with laziness. I thought that in another thread we agreed that there are no "natural" evaluation order. (As I side note: I think that cognitively laziness is easier because humans glance, not drill, but that's a topic for behavior scientists to figure out).
@haskman I'm talking about data strucutres, not algorithms. The data structure I'm talking about, namely, is "stream".
In Haskell it's just `Cons a (Stream a)` and you write code (algorithms) over it as normal. In Ocaml it's `type 'Cons of 'a * (unit -> 'a stream)`.
Same goes for zippers.
I'm not smart enough to know fancy algorithms, but if functions over possibly infinite datums, you can imagine how explicit thunking makes things worse.
https://github.com/lurk-lab/straume/blob/main/Straume/Chunk.lean all of this machinery can be avoided entirely with laziness, for example.
@jonn @dpwiz Can you be more specific? What algorithm are you thinking of that's easier to write and understand with laziness?