Add laws for Foldable instances #128
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## master #128 +/- ##
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Coverage ? 55.65%
Complexity ? 211
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Files ? 90
Lines ? 1335
Branches ? 174
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Hits ? 743
Misses ? 518
Partials ? 74
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| fun <G, A, B> foldM(MG: Monad<G>, fa: HK<F, A>, z: B, f: (B, A) -> HK<G, B>): HK<G, B> { | ||
| return foldL(fa, MG.pure(z), { gb, a -> MG.flatMap(gb) { f(it, a) } }) | ||
| } | ||
| fun <G, A, B> foldM(MG: Monad<G>, fa: HK<F, A>, z: B, f: (B, A) -> HK<G, B>): HK<G, B> = |
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should this contain the default param value = monad()?
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what if it is expressed as an extension function?
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That might work. I'm starting to seriously consider that we'd remove several headaches if we were to express all functions bar the pure virtual ones as extensions.
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I've added them to this PR #129
| fun <G, A, B> foldMapM(MG: Monad<G>, bb: Monoid<B>, fa: HK<F, A>, f: (A) -> HK<G, B>) : HK<G, B> { | ||
| return foldM(MG, fa, bb.empty(), { b, a -> MG.map(f(a)) { bb.combine(b, it) } }) | ||
| } | ||
| fun <G, A, B> foldMapM(MG: Monad<G>, bb: Monoid<B>, fa: HK<F, A>, f: (A) -> HK<G, B>) : HK<G, B> = |
Working towards #103
In this PR the test for all Foldable laws are added. I'll add the last for Traverse on the next PR, so we can have both reviewed separately.
Reference: https://github.com/typelevel/cats/blob/master/laws/src/main/scala/cats/laws/TraverseLaws.scala
I have tested them with Id and Coproduct, which will get Traverse laws on the next PR instead.