FreeC implementation #1048

nomisRev · 2018-10-14T15:38:05Z

This PR is the starting point of a FS2 port or FS2 inspired stream lib.

In discussion with @raulraja we had the idea to move this to arrow-free as a replacement for the current Free implementation since we can then provide instance up to MonadDefer (and later also Sync).

If we are to move FreeC to arrow-free I'd like to improve the Result and ViewL code. Does any1 know if we could do something with inline classes to create sealed class wrappers without runtime overhead? I am assuming since they're going to be nested that they'll auto-box?

codecov · 2018-10-14T20:40:04Z

Codecov Report

Merging #1048 into master will decrease coverage by 0.11%.
The diff coverage is 36.36%.

@@             Coverage Diff              @@
##             master    #1048      +/-   ##
============================================
- Coverage     42.39%   42.28%   -0.12%     
- Complexity      750      755       +5     
============================================
  Files           360      365       +5     
  Lines          9989    10219     +230     
  Branches       1082     1147      +65     
============================================
+ Hits           4235     4321      +86     
- Misses         5439     5562     +123     
- Partials        315      336      +21

Impacted Files	Coverage Δ	Complexity Δ
...core/arrow-free/src/main/kotlin/arrow/free/Free.kt	`57.14% <ø> (ø)`	`0 <0> (ø)`	⬇️
...-streams/src/main/kotlin/arrow/effects/ExitCode.kt	`0% <0%> (ø)`	`0 <0> (?)`
...re/arrow-core/src/main/kotlin/arrow/core/Option.kt	`59.67% <0%> (ø)`	`22 <0> (ø)`	⬇️
.../src/main/kotlin/arrow/streams/CompositeFailure.kt	`0% <0%> (ø)`	`0 <0> (?)`
...rc/main/kotlin/arrow/streams/internal/instances.kt	`34.78% <34.78%> (ø)`	`0 <0> (?)`
...ms/src/main/kotlin/arrow/streams/internal/FreeC.kt	`39.89% <39.89%> (ø)`	`4 <4> (?)`
...ms/src/main/kotlin/arrow/streams/internal/Token.kt	`50% <50%> (ø)`	`1 <1> (?)`
...ics/src/main/kotlin/arrow/optics/instances/mapk.kt	`86.36% <0%> (-4.55%)`	`0% <0%> (ø)`
... and 6 more

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raulraja · 2018-10-15T17:07:59Z

@nomisRev AFAIK inline classes properties of erasing the wrapper are not applied to any kind of generic container and they only work with primitives but @pakoito may know more.

raulraja

Great start!

raulraja · 2018-10-15T17:08:39Z

modules/core/arrow-core/src/main/kotlin/arrow/core/Option.kt

@@ -191,7 +191,7 @@ fun <T> Option<T>.getOrElse(default: () -> T): T = fold({ default() }, ::identit
 *
 * @param alternative the default option if this is empty.
 */
-inline fun <A, B : A> OptionOf<B>.orElse(alternative: () -> Option<B>): Option<B> = if (fix().isEmpty()) alternative() else fix()
+inline fun <A> OptionOf<A>.orElse(alternative: () -> Option<A>): Option<A> = if (fix().isEmpty()) alternative() else fix()


raulraja · 2018-10-15T17:12:22Z

modules/streams/arrow-streams/src/test/kotlin/arrow/streams/internal/FreeCTest.kt

+}
+
+internal object EitherToTry : FunctionK<EitherPartialOf<Throwable>, ForTry> {
+  override fun <A> invoke(fa: Kind<EitherPartialOf<Throwable>, A>): Kind<ForTry, A> =


We have Try#toEither. Perhaps this implementation can be exposed in the core as Either<Throwable, A>.toTry()

Yeah sure. Btw should we add FunctionK instances like this one to Arrow? Or is there a ticket for this that I missed?

@nomisRev they won't hurt, but it isn't a priority. Only the ones between Try/Either/Option and maybe ListK may be more interesting for now.

@pakoito I could quickly add them in this PR.

Just a friendly reminder that in 0.8.0 the use of ListK and wrappers of one type arguments are rarely seen in user code unless they have polymorphic functions that expect values in the kind hierarchy.

raulraja

Awesome stuff! 👏

raulraja · 2018-10-19T13:01:50Z

modules/streams/arrow-streams/build.gradle

@@ -0,0 +1,14 @@
+dependencies {


🎉 it's alive!

raulraja · 2018-10-19T13:03:54Z

modules/streams/arrow-streams/src/main/kotlin/arrow/streams/internal/FreeC.kt

+import arrow.typeclasses.MonadError
+
+/**
+ * Free Monad with Catch (and Interruption).


We should mention and include fs2 here https://github.com/arrow-kt/arrow/blob/master/LICENSE#L20

raulraja · 2018-10-19T13:05:25Z

modules/streams/arrow-streams/src/main/kotlin/arrow/streams/internal/FreeC.kt

+  }
+)
+
+/**  @higherkind doesn't respect access modifier **/


once it is migrated to the meta processor you may be able to get that info

raulraja · 2018-10-19T13:08:13Z

modules/streams/arrow-streams/src/main/kotlin/arrow/streams/internal/instances.kt

+    this.fix().map(f)
+}
+
+internal fun <F> FreeC.Companion.applicative(): Applicative<FreeCPartialOf<F>> = object : FreeCApplicative<F> { }


Are these handwritten because they are internal? After 0.8.0 we should be able to encode internal instances in the ExtensionProcessor so all the syntax they export it's also internal.

raulraja · 2018-10-19T13:09:23Z

modules/streams/arrow-streams/src/test/kotlin/arrow/streams/internal/FreeCTest.kt

+      EQ_EITHER = Eq { a, b -> a.run(Try.monadError()) == b.run(Try.monadError()) }
+    ))
+
+    testLaws(MonadDeferLaws.laws(


I thought the laws where encoded such as if you just test the MonadDeferLaws it will include all others in its hierarchy.

Yes, they're. This is left over from when I was debugging combinators in smaller sets at a time :D

raulraja · 2018-10-19T13:10:00Z

modules/streams/arrow-streams/src/test/kotlin/arrow/streams/internal/FreeCTest.kt

+      }
+    }
+
+    "Running an suspended value"{


raulraja · 2018-10-19T13:12:07Z

modules/streams/arrow-streams/src/test/kotlin/arrow/streams/internal/FreeCTest.kt

+}
+
+internal object EitherToTry : FunctionK<EitherPartialOf<Throwable>, ForTry> {
+  override fun <A> invoke(fa: Kind<EitherPartialOf<Throwable>, A>): Kind<ForTry, A> =


Just a friendly reminder that in 0.8.0 the use of ListK and wrappers of one type arguments are rarely seen in user code unless they have polymorphic functions that expect values in the kind hierarchy.

raulraja · 2018-10-19T18:17:32Z

@nomisRev This is ready to go once you rebase from master

… in matches over GADTs

nomisRev · 2018-11-09T12:33:22Z

@raulraja could you review again? Also API / encoding of FreeC. I think this is about as good as it gets and if everyone agrees I'll move it to arrow-free.

raulraja

This is excellent Simon! Kudos!, Our Free impl is now one step closer to have more superpowers than the scala cats one which had limited us In Freestyle big time

raulraja · 2018-11-09T12:43:19Z

modules/streams/arrow-streams/src/main/kotlin/arrow/streams/internal/FreeC.kt

+      }
+      is Fail<*, R> -> free
+      is Interrupted<*, R, *> -> free
+      else -> throw AssertionError("Unreachable")


In the event that this is ever thrown we should indicate in the exception message that this is potentially caused by a bug and provide a link to report it in the arrow issue tracker.

nomisRev force-pushed the fs2-port-poc branch from 8f3a497 to a991fe9 Compare October 14, 2018 20:14

raulraja approved these changes Oct 15, 2018

View reviewed changes

raulraja approved these changes Oct 19, 2018

View reviewed changes

nomisRev and others added 13 commits October 21, 2018 08:12

There was an attempt

01a3bb9

Emulated sealed interfaces

7acb863

dirty version that compiles with multiple casts due to poor inference…

7802029

… in matches over GADTs

Cleanup FreeC and complete port FS2

222b0b2

Cleanup FreeC and complete port FS2

f791700

Fix infinite loop mk function and some tests

8624e2e

Fix incorrect typeclass implementation

f920695

Add missing methods

de182e2

Add documentation

a1e49dc

infographic

3f869d5

Fix detekt

caafb2c

Added bracketcase

37dc39a

Add FS2 LICENSE

1358942

nomisRev force-pushed the fs2-port-poc branch from 41506b2 to 1358942 Compare October 21, 2018 12:15

nomisRev and others added 6 commits October 21, 2018 08:20

Clean up tests

545dca4

Merge branch 'master' into fs2-port-poc

3bdf812

Fix test

bb2b4b2

Fix visibility of public API

578f2ee

Clean up FreeC & make stack safe

a018b77

Merge branch 'master' into fs2-port-poc

f82dac6

raulraja approved these changes Nov 9, 2018

View reviewed changes

raulraja merged commit 2039fd8 into master Nov 9, 2018

raulraja deleted the fs2-port-poc branch November 9, 2018 16:20

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FreeC implementation #1048

FreeC implementation #1048

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FreeC implementation #1048

FreeC implementation #1048

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