unisonweb/unison

Next generation programming language, currently in development

sfultong

@sfultong

I suppose you could build a mostly-pure OO language that compiled down to Unison Terms

not sure how you'd handle effects

Odomontois

@Odomontois

in Unison, all values, including functions, are serializable

does that mean unison would have something like distributed garbage collector? How could this be implemented?

Rúnar

@runarorama

@Odomontois I'm not sure what you mean by distributed gc or why we'd need that. Can you elaborate? Serialization is just implemented as a function of type forall a. a -> Bytes. We're hoping to constrain this type later on so we don't lose parametricity.

Odomontois

@Odomontois

Tutorial says you have node-level caching for transmitted data. So I assume you won't allocate boxed data that is referenced by several messages, that were sen't from the same source in different transfer s

So my question is: how would this cache be cleared

And how single node GC will interact with caches on other nodes

Chris Gibbs

@atacratic

@Odomontois do you mean the cache of unison terms, indexed by their hash? I guess a simple strategy of kicking elements out of that cache when they get old would work. It's a different thing to the set of terms that are known in the local codebase. And the term for a given hash is immutable.

Rúnar

@runarorama

The cache is just an LRU list and a hash table. It's cleared by removing the least recently used objects. GC is separate and is a local gc process. At the moment we piggy-back on Haskell's garbage collector.

There's not going to be any interaction at that level between nodes.

i.e. Unison does not implement a distributed memory other than that hashes are an address into a kind of "global virtual memory"

Chris Gibbs

@atacratic

https://medium.com/darklang/real-problems-with-functional-languages-efe668c5264a

Type propagation stuff sounds familiar, but would like to know more - is it that each http route handler is treated like its own program? What about state that persists between requests? Error rail sounds cool - would be interesting to compare with Abort ability.

Chris Gibbs

@atacratic

Interesting to think about what the Dark partial type propagation stuff would look like in unison: categorize todos for a patch by which connected component of the term graph they're in; stop and run your program after propagating only through one component.

Chris Gibbs

@atacratic

I guess the 'error rail' is a bit like implicitly inserting

...inserting Optional a ->{Abort} a conversions.

Paul Chiusano

@pchiusano

@atacratic just noticed, prettyprinter inserts () and Pair imports, but I think those probably aren’t needed as the parser converts tuple syntax directly to them… Pair constructor might sometimes be used directly but I’d say a simple fix is to just always use that qualified

Paul Chiusano

@pchiusano

re: type propagation, in Unison, you aren’t forced to propagate a change to “your whole codebase” before you can run anything… only to the dependents you actually want to run :) This comes more or less for free with the codebase model we have.

Chris Gibbs

@atacratic

@pchiusano thing 1: ha, ok, will do simple fix! Thing 2: awesome! 😁

Paul Chiusano

@pchiusano

@atacratic 😎

Tony Morris

@tonymorris_gitlab

Have you considered using lens on e.g. some parts of the syntax tree?

Paul Chiusano

@pchiusano

@atacratic am excited for this PR adding color to the view output :)

Chris Gibbs

@atacratic

@pchiusano yeah, this one has been very gratifying! 😁

Simon Hafner

@reactormonk

With an algebraic effect system (that's what unison has from what I've read (?)) how do you implement sequence?

Rúnar

@runarorama

with algebraic effects, sequence is id

Rúnar

@runarorama

x : '{State Nat} [()]
x = '[put 10, put 11, put 123]

and traverse is just map

Simon Hafner

@reactormonk

Makes sense.

How do you deal with cases where the ordering of effects matters? E.g. State with ExceptT

Rúnar

@runarorama

Those cases don't exist in Unison. {State s, Error e} means that a program can manipulate state of type s or throw an error of type e at any time.

whereas monad transformers represent monad products, you can think of Unison as having monad coproducts.

Rúnar

@runarorama

So I guess {State s, Error e} is essentially ExceptT e (State s)

Whereas to get the semantics of StateT s (Either e), you'd have to handle a State s into Error e.

Stacy Curl

@stacycurl

How do you compose interpreters ? can you perform partial interpretation, i.e. of a subset of the effects ?

Rúnar

@runarorama

interpreters/handlers are just functions

You can handle a subset of the effects, and even just a subset of the constructors of a given effect

so like you could handle State gets, but leave puts alone

Stacy Curl

@stacycurl

ZIO has something similar but it’s implemented (last time I lurked) by deferring until all effects have been handled, you can’t observe anything interesting about a partially evaluated effect type.

I think internally something like `ZIO[State with Error, A].contramap[State](state => state with error): ZIO[State] is happening.

Simon Hafner

@reactormonk

So algebraic effects are more like imperative programming with guard from arbitrary effects via function tags?

... in terms of side effects. Still got immutable structures etc. by default

Rúnar

@runarorama

algebraic effects are semantically like free monads or tagless final monad coproducts or the like

syntactically they're like imperative programming with function tags

you can think of Unison's "abilities" as being syntactic sugar for a free monad coproduct

Paul Chiusano

@pchiusano

Hi folks, everyone here is invited to our Slack: https://join.slack.com/t/unisonlanguage/shared_invite/enQtNzAyMTQ4ODA0MDM4LWYxZTNkMGUxMDEzNTg3NTMxNjMxOGM2Zjg4ODFjM2RhNGY0OGU2NTMzYmQ1YWIwN2Y0YTc1NjQ1NjgzYzEzOWI

Arya Irani

@aryairani

... and in that Slack, we've released an alpha version of Unison to whoever's interested! Come check it out.

Bruno Berisso

@BrunoBerisso

Hi everyone

I'm starting to play around with unison but I'm a bit lost... Is there some docs about the REPL? I was able to get it running without problems but I'm not sure what it does, looking at the commands it doesn't seems to be a "normal" REPL

Maybe I'm missing some of the docs? Is there a basic example-like tuotorial to get something going quickly?
Thanks

Paul Chiusano

@pchiusano

Hi @BrunoBerisso we are moving discussion over to Slack, join link is tiny.cc/unisonslack and if you join the #alphatesting channel there we've got link to documentation for getting started that covers all this! :)

Bruno Berisso

@BrunoBerisso

Awesome thanks

Paul Chiusano

@pchiusano

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