Add support for bidirectional effects #29

long-long-float · 2020-10-15T07:33:41Z

This PR adds the feature of bidirectional control flow to the Effekt language. The feature is inspired by the paper

"Handling bidirectional control flow".
Yizhou Zhang, Guido Salvaneschi, and Andrew C. Myers. OOPSLA'20 (PDF).

long-long-float · 2020-10-15T07:39:57Z

I'll rebase to solve conflicts.

b-studios · 2020-10-16T15:14:58Z

Could you maybe add a couple of example files with expected output check files to the examples/pos directory?

b-studios

Looks already pretty good to me. I added a few suggested changes that would be great if you could incorporate them. As already mentioned, it would also be great to have a few examples that illustrate the new feature.

In the changes I propose to reject programs where resume is used in the wrong way. I think that is easiest for now. If you would like to stick with the automatic adaption to the correct kind, I think we need another, consistent way that actually changes the terms.

shared/src/main/scala/effekt/Parser.scala

shared/src/main/scala/effekt/Namer.scala

shared/src/main/scala/effekt/Typer.scala

shared/src/main/scala/effekt/core/Transformer.scala

lib/effekt_runtime.js

long-long-float · 2020-10-30T17:49:11Z

@b-studios I applied suggested changes and added an example. Please review it.

b-studios · 2020-10-30T18:48:40Z

closing and reopening to trigger CI

b-studios · 2020-11-07T11:17:12Z

Thank you @long-long-float for your contributions! As you will see (after fixing my accidental bug missing a brace), there are still a few tests that do not pass and I cannot merge your feature without the CI going through.

The Effekt language has multiple backends and your bidirectionality feature only supports one of them (JavaScript), which is fine. It is expected that your new test fails on all other backends. You can see how the bidirectionality test can be disabled in the other backends here:

effekt/jvm/src/test/scala/effekt/ChezSchemeTests.scala

Lines 18 to 28 in 581b111

    
           lazy val ignored: List[File] = List( 
        
             examplesDir / "pos" / "arrays.effekt", 
        
             examplesDir / "pos" / "maps.effekt", 
        
             // unsafe continuations are not yet supported in our Chez backend 
        
             examplesDir / "pos" / "unsafe_cont.effekt", 
        
             examplesDir / "pos" / "propagators.effekt", 
        
             // the number representations differ in JS and Chez 
        
             examplesDir / "casestudies" / "ad.md" 
        
           )

(If you are interested, you can of course also consider supporting the other backends -- like Chez Scheme, but this is not strictly necessary for now).

However, all other tests that are not concerned with bidirectionality should still pass. Maybe you can look into this? If you have any questions, I am happy to assist.

b-studios · 2020-11-07T11:18:36Z

shared/src/main/scala/effekt/source/Tree.scala

@@ -100,7 +100,7 @@ case class VarDef(id: IdDef, annot: Option[ValueType], binding: Stmt) extends De
 case class EffDef(id: IdDef, ops: List[Operation]) extends Def {
  type symbol = symbols.UserEffect
 }
-case class Operation(id: Id, tparams: List[Id], params: List[ValueParams], ret: Effectful) extends Definition {
+case class Operation(id: IdDef, tparams: List[Id], params: List[ValueParams], ret: Effectful) extends Definition 


Oh.. I forgot the opening brace here, when editing this in the online editor. @long-long-float could you fix this in your branch?

long-long-float · 2020-11-10T04:00:04Z

@b-studios The CI fails and says an error [error] examples/neg/existential_effect_leaks.effekt:22:1: Unhandled effects: GiveInt. My modification may effect this. Should I fix this?

b-studios · 2020-11-10T07:45:14Z

Yes, it should warn about an effect leaving its scope as you can see in the check file. Would be great if you could look into this

long-long-float · 2020-11-15T14:17:09Z

@b-studios I fixed the test case of examples/neg/existential_effect_leaks.effekt, but other cases are faild.

[info]   - unbound_type.effekt (lift) *** FAILED *** (145 milliseconds)
[info]     "... pos: Position): A
[info]     ^[^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^]
[info]     " did not equal "... pos: Position): A
[info]     ^[]
[info]     " (ChezSchemeTests.scala:62)
[info]     Analysis:
[info]     "... pos: Position): A
[info] ^[^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^]
[info] " -> "... pos: Position): A
[info] ^[]

I Investigated the cause and guess that the position of the type of an operator (ret: Effectful) is not set (but I don't know how to set it.)

b-studios · 2020-11-15T15:39:23Z

Update: I just modified Namer in master so you only need to rebase. This should hopefully also solve the problem you described here.

b-studios · 2020-11-15T15:44:04Z

shared/src/main/scala/effekt/Typer.scala

@@ -571,7 +579,13 @@ class Typer extends Phase[Module, Module] { typer =>
      effs = (effs ++ (stmtEffs -- handled))
    }

-    (params zip args) foreach { case (ps, as) => checkArgumentSection(ps, as) }
+    (params zip args) foreach {
+      // Special case - treat 1st param type () => T as T


Maybe you could expand a bit on this comment (and maybe add an example to examples/pos?). This part is really the most tricky bit, I believe.

(the detailed explanation is not necessary for merging into master, but would be nice at some point)

I reconsidered about it, it is unnecessary. So I removed it.

Co-authored-by: Jonathan <jonathan@b-studios.de>

…ctively

long-long-float · 2020-11-16T07:43:38Z

@b-studios All tests are passed! Thanks for your advice.

b-studios · 2020-11-16T08:51:46Z

Thanks for your contributions @long-long-float, which I'll merge now!

If you want, you could add more examples of the feature, potentially translating the examples from the original paper? The paper is presented this week at OOPSLA and having translated their examples could facilitate discussion.

long-long-float · 2020-11-16T09:31:35Z

Of course I'm creating more examples for the paper 😄

b-studios · 2020-11-16T21:42:02Z

@long-long-float Just to be clear: What I meant is: could you take examples from the existing paper by Zhang er al., translate them to Effekt and add them to this repository?

long-long-float · 2020-11-17T01:58:36Z

Yes, I'm translating examples from the existing paper by Zhang er al., to Effekt.

Generators: I'm translating it.
Async-await: I considered that it cannot be because Effekt doesn't have first-class function.
Ping and Pong: I translated it as examples/pos/bidirectional.effekt.

b-studios · 2020-11-17T15:23:13Z

Hey, thanks! I added a quick translation of the iterator example here to talk about it with people at the OOPLSA conference.

long-long-float · 2020-11-18T08:05:32Z

Cool! I have just translated the same example here.

b-studios · 2020-11-18T09:04:54Z

That's great. Since you are the expert on bidirectional effects in the Effekt language, do you want to document it on the website? We have a separate repository for that. I added a quick stub, but there could be much detailed explanation about what bidirectional effects motivates, how they work and how they interact with effect polymorphism:

https://github.com/effekt-lang/effekt-website/blob/master/docs/bidirectional.md

long-long-float · 2020-11-19T03:15:30Z

Sure, I want to do. I'll write it with my master thesis.

Supersedes and closes #29 Co-authored-by: @edding4500

long-long-float force-pushed the bidirectional branch 2 times, most recently from 71ab306 to 5a77660 Compare October 15, 2020 07:59

long-long-float changed the title ~~Supports Bidirectional-effect~~ WIP: Supports Bidirectional-effect Oct 15, 2020

long-long-float force-pushed the bidirectional branch from 5a77660 to a1aab85 Compare October 15, 2020 08:09

long-long-float changed the title ~~WIP: Supports Bidirectional-effect~~ Supports Bidirectional-effect Oct 15, 2020

b-studios requested changes Oct 20, 2020

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b-studios closed this Oct 30, 2020

b-studios reopened this Oct 30, 2020

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b-studios changed the title ~~Supports Bidirectional-effect~~ Add support for bidirectional effects Nov 15, 2020

long-long-float added 8 commits November 16, 2020 16:13

Fix parser

0d94363

wip

9cd3ee7

fix

aa07cfa

Modify to be able resume to take block argument.

5c80077

Remove effects from the block argument of resume

51b011c

Fix the type of resume

e1a3db4

Fix runtime

1f6cd9d

Add desugarer to convert resume (x) to resume {x} (not working)

f7cd88e

long-long-float and others added 9 commits November 16, 2020 16:14

Fix typer to accept resume(x)

f649bb3

Clean up codes

a11ec4a

Remove unused field isEffectful

decd291

Combine rules of resumExpr

06f109b

Co-authored-by: Jonathan <jonathan@b-studios.de>

Apply suggested changes

12710d5

Add an example of bidirectional

1a62194

Change id type of Definitions and References to IdDef and IdRef respe…

0700ab9

…ctively

Ignore a test of bidirectional in ChezScheme

69cf083

Restore the needed line

ff5ea1a

long-long-float force-pushed the bidirectional branch from 47a79b5 to ff5ea1a Compare November 16, 2020 07:16

Remove unnecessary type checking

163ef5e

b-studios approved these changes Nov 16, 2020

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b-studios merged commit d5dcbf6 into effekt-lang:master Nov 16, 2020

b-studios added a commit that referenced this pull request Sep 27, 2022

Homogenize paths for windows

b184cdf

Supersedes and closes #29 Co-authored-by: @edding4500

b-studios mentioned this pull request Sep 27, 2022

Homogenize paths for windows #158

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Add support for bidirectional effects #29

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Add support for bidirectional effects #29

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