Add Foldable and Traversable instanced for most common classes #101

pakoito · 2017-05-29T01:38:59Z

This PR adds Foldable and Traversable instances to the following classes:

Validated
Coproduct
EitherT
Either
OptionT
Ior
Try
Id

There is some magic involved in OptionT and EitherT to simulate lambda types. This abstraction doesn't leak outside the package.

…derganger

codecov · 2017-05-29T01:43:39Z

Codecov Report

Merging #101 into master will decrease coverage by 1.74%.
The diff coverage is 55.04%.

@@             Coverage Diff              @@
##             master     #101      +/-   ##
============================================
- Coverage     54.33%   52.58%   -1.75%     
- Complexity      146      164      +18     
============================================
  Files            67       76       +9     
  Lines           935     1025      +90     
  Branches        137      149      +12     
============================================
+ Hits            508      539      +31     
- Misses          372      429      +57     
- Partials         55       57       +2

Impacted Files	Coverage Δ	Complexity Δ
...kotlin/katz/instances/ValidatedApplicativeError.kt	`60% <ø> (-6.67%)`	`2 <0> (ø)`
katz/src/main/kotlin/katz/instances/Traverse.kt	`0% <ø> (ø)`	`0 <0> (ø)`	⬇️
...atz/src/main/kotlin/katz/instances/EitherTMonad.kt	`80% <ø> (-1.25%)`	`4 <0> (-1)`
...atz/src/main/kotlin/katz/instances/OptionTMonad.kt	`35.71% <ø> (-4.29%)`	`4 <0> (+1)`
katz/src/main/kotlin/katz/instances/IorMonad.kt	`17.64% <ø> (-4.58%)`	`3 <0> (ø)`
...tz/src/main/kotlin/katz/instances/TryMonadError.kt	`44.44% <ø> (-5.56%)`	`0 <0> (ø)`
katz/src/main/kotlin/katz/instances/EitherMonad.kt	`33.33% <ø> (ø)`	`2 <0> (ø)`	⬇️
...atz/src/main/kotlin/katz/instances/WriterTMonad.kt	`75% <ø> (-1.93%)`	`5 <0> (+1)`
katz/src/main/kotlin/katz/instances/OptionMonad.kt	`70% <ø> (-2.73%)`	`0 <0> (ø)`
...rc/main/kotlin/katz/instances/NonEmptyListMonad.kt	`76.92% <ø> (-1.65%)`	`0 <0> (ø)`
... and 40 more

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…ions

pakoito · 2017-05-29T02:51:19Z

I've moved all ev() methods from the monads into the data classes. They were reused in typeclass instances other than monads. Better have them on a central spot.

ffgiraldez

good job @pakoito 👍 , only a few comments in order to understand better and styles.

ffgiraldez · 2017-05-29T05:55:48Z

katz/src/main/kotlin/katz/data/Coproduct.kt

+    fun <B> foldR(lb: Eval<B>, f: (A, Eval<B>) -> Eval<B>, FF: Foldable<F>, FG: Foldable<G>): Eval<B> =
+            run.fold({ FF.foldR(it, lb, f) }, { FG.foldR(it, lb, f) })
+
+    fun <H, B> traverse(f: (A) -> HK<H, B>, GA: Applicative<H>, FT: Traverse<F>, GT: Traverse<G>) =


IMO It's better for a library POV always specify the returning type instead of infer it.

ffgiraldez · 2017-05-29T05:57:13Z

katz/src/main/kotlin/katz/data/Cokleisli.kt

@@ -7,6 +7,8 @@ typealias CokleisiFun<F, A, B> = (HK<F, A>) -> B

 typealias CoreaderT<F, A, B> = Cokleisli<F, A, B>

+fun <F, A, B> CokleisiTKind<F, A, B>.ev(): Cokleisli<F, A, B> = this as Cokleisli<F, A, B>


why moving it to top instead of leave it at bottom?

For consistency. At the moment the ev() is available for all HK types. If it's at the bottom you have to make sure to add methods right before it, which it's a practice that may not be followed.

With this change, just from opening the file you know your alias and casts without having to scroll.

ffgiraldez · 2017-05-29T06:02:45Z

katz/src/main/kotlin/katz/instances/Composed.kt

+package katz
+
+/**
+ * https://www.youtube.com/watch?v=wvSP5qYiz4Y


Really 😄

I've been know to comment worse :D

ffgiraldez · 2017-05-29T06:08:43Z

katz/src/main/kotlin/katz/instances/Composed.kt

+    }
+}
+
+inline fun <F, reified G> Foldable<F>.compose(GT: Foldable<G> = foldable<G>()) =


just style could be in the same line

also please specify the return type

I'm following the practice of breaking to the next line to separate signature and content. You can see the implementation at a glance even for short methods, rather than scrolling horizontally.

I may have not been super consistent for shorter methods. I'll try to from now on.

ffgiraldez · 2017-05-29T06:16:51Z

katz/src/main/kotlin/katz/instances/Composed.kt

+inline fun <F, reified G> Foldable<F>.compose(GT: Foldable<G> = foldable<G>()) =
+        ComposedFoldable(this, GT)
+
+data class ComposedTraverse<F, G>(val FT: Traverse<F>, val GT: Traverse<G>, val GA: Applicative<G>, val CF: ComposedFoldable<F, G> = ComposedFoldable(FT, GT))


Please @pakoito could you explain why ComposeFoldable is open but not a data class and ComposedTraverse is not open but a data class?

I did a refactor and forgot to fix it. Lemme go through it.

ffgiraldez · 2017-05-29T06:18:09Z

katz/src/main/kotlin/katz/instances/Composed.kt

+    override fun <H, A, B> traverse(fa: HK<ComposedType<F, G>, A>, f: (A) -> HK<H, B>, HA: Applicative<H>): HK<H, HK<ComposedType<F, G>, B>> =
+            HA.map(FT.traverse(fa.lower(), { ga -> GT.traverse(ga, f, HA) }, HA), { it.lift() })
+
+    fun <H, A, B> traverseC(fa: HK<F, HK<G, A>>, f: (A) -> HK<H, B>, HA: Applicative<H>) =


please specify the return type

ffgiraldez · 2017-05-29T06:18:58Z

katz/src/main/kotlin/katz/instances/Composed.kt

+    }
+}
+
+inline fun <F, reified G> Traverse<F>.compose(GT: Traverse<G> = traverse<G>(), GA: Applicative<G> = applicative<G>()) =


please specify the return type

ffgiraldez · 2017-05-29T06:25:45Z

katz/src/main/kotlin/katz/instances/Function0Bimonad.kt

@@ -1,5 +1,9 @@
 package katz

+fun <A> (() -> A).k(): HK<Function0.F, A> = Function0(this)
+
+fun <A> HK<Function0.F, A>.ev() = (this as Function0<A>).f


please specify the return type

ffgiraldez · 2017-05-29T06:31:27Z

katz/src/main/kotlin/katz/instances/Composed.kt

+/**
+ * https://www.youtube.com/watch?v=wvSP5qYiz4Y
+ */
+interface ComposedType<out F, out G>


could it be private or break implicit magic?
My reason it's not expose it when you import kats that would confuse people that use it.

It cannot be private, the compiler marks other instances that expose it like the constructor of the composed types. It also disallows lower(), which is used by the classes that use the composed constructs: https://github.com/FineCinnamon/Katz/blob/c4f790b9dff9201a82d338b9520860427e3289cf/katz/src/main/kotlin/katz/data/EitherT.kt#L72

pakoito added 14 commits May 29, 2017 00:25

Add Composed types

03e8c67

Add Traverse instance for Ior

2eb5336

Add global lookup for Foldable and Traverse

3462421

Add Traverse instance for Try

b222231

Add Traverse instance for OptionT

c0d68c2

Add Traverse instance for Validated

7b36c0a

Add missing Traverse instance for EitherT

37c48c2

Add Traverse instance for Coproduct

5e0e42b

Add Traverse instance for EitherT

644097b

Add Traverse instance for Id

392c45d

Fix an implicit lookup miss

eba936f

Add EitherT tests for traverse and fold

1c5e10f

Cleanup unnecessary parameters

513b9ef

Remove redundant parameters

cfd82fc

pakoito requested review from raulraja, ffgiraldez and JorgeCastilloPrz May 29, 2017 01:38

pakoito and others added 3 commits May 29, 2017 02:39

Merge branch 'master' into paco-folderganger

25c6806

Fix detekt

552be60

Merge remote-tracking branch 'origin/paco-folderganger' into paco-fol…

85a63b5

…derganger

pakoito added 7 commits May 29, 2017 02:49

Remove unnecessary parameter

a4471f8

Remove behaviour leak from EitherT and OptionT

9f7c7bb

Add reified constructors to composed types

271606b

Rename ComposeType API

15ebe54

Refactor Compose API to become an interface tag + two extension funct…

3e1d9f7

…ions

Refactor .ev() to be atop of files

465cf49

Fix remaining ev()

89267c7

Fix extension functions

ae0ef30

Add suppression for safe unchecked cast

c4f790b

ffgiraldez requested changes May 29, 2017

View reviewed changes

pakoito added 2 commits May 29, 2017 13:31

Add format consistency pass for breaking to next line on methods

5c7b546

Add missing format

b5ea191

pakoito mentioned this pull request May 29, 2017

Creating a new data type #102

Closed

raulraja approved these changes May 29, 2017

View reviewed changes

Add missing inference

4be57d3

ffgiraldez approved these changes May 29, 2017

View reviewed changes

ffgiraldez merged commit 092c34c into master May 29, 2017

ffgiraldez deleted the paco-folderganger branch May 29, 2017 17:29

pakoito mentioned this pull request May 29, 2017

Add missing tests and laws for Foldable and Traverse instances #103

Closed

rachelcarmena added a commit that referenced this pull request Feb 24, 2021

Doc: Fix broken links (#101)

a44647f

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Add Foldable and Traversable instanced for most common classes #101

Add Foldable and Traversable instanced for most common classes #101

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pakoito May 29, 2017

		@@ -7,6 +7,8 @@ typealias CokleisiFun<F, A, B> = (HK<F, A>) -> B

		typealias CoreaderT<F, A, B> = Cokleisli<F, A, B>

		fun <F, A, B> CokleisiTKind<F, A, B>.ev(): Cokleisli<F, A, B> = this as Cokleisli<F, A, B>

Add Foldable and Traversable instanced for most common classes #101

Add Foldable and Traversable instanced for most common classes #101

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