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Add find operation to FoldableOps #118

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Add find operation to FoldableOps #118

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caa6c34
Add find operation to FoldableOps
bilki Jul 4, 2019
efdb5d3
Merge branch 'master' into basis-find
andyscott Sep 5, 2019
e1f5852
Merge branch 'master' into basis-find
andyscott Oct 28, 2019
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6 changes: 6 additions & 0 deletions modules/core/src/main/scala/higherkindness/droste/basis.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,9 @@ trait Project[F[_], R] { self =>
F: Foldable[F]): U =
Project.collect[F, R, U, B](r)(pf)

def find[B](r: R)(pf: PartialFunction[R, B])(implicit F: Foldable[F]): Option[B] =
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I'd prefer the Boolean variation, as it's more consistent with find methods in the Scala stdlib.

Project.find[F, R, B](r)(pf)

def contains(r: R, c: R)(implicit R: Eq[R], F: Foldable[F]): Boolean =
Project.contains[F, R](r, c)

Expand Down Expand Up @@ -73,6 +76,9 @@ object Project extends FloatingBasisInstances[Project] {
pf.lift(_)
.foldRight[U](U.algebra(NilF))((a, b) => U.algebra(ConsF(a, b))))

def find[F[_], R, B](r: R)(pf: PartialFunction[R, B])(implicit P: Project[F, R], F: Foldable[F]): Option[B] =
foldMap[F, R, Option[B] @@ Tags.First](r)(pf.lift(_).first).unwrap

def contains[F[_], R](
r: R,
c: R)(implicit P: Project[F, R], R: Eq[R], F: Foldable[F]): Boolean =
Expand Down
3 changes: 3 additions & 0 deletions modules/core/src/main/scala/higherkindness/droste/syntax/package.scala
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Expand Up @@ -174,6 +174,9 @@ object ProjectSyntax {
implicit U: Basis[ListF[B, ?], U]): U =
Project.collect[F, T, U, B](self)(pf)

def find[B](pf: PartialFunction[T, B]): Option[B] =
Project.find(self)(pf)

def contains(c: T)(implicit T: Eq[T]): Boolean =
Project.contains(self, c)

Expand Down
11 changes: 11 additions & 0 deletions modules/core/src/main/scala/higherkindness/droste/util/newtypes.scala
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Expand Up @@ -10,6 +10,7 @@ object newtypes {
object Tags {
sealed trait Conjunction
sealed trait Disjunction
sealed trait First
}

implicit class BooleanOps(b: Boolean) {
Expand All @@ -34,4 +35,14 @@ object newtypes {
b: Boolean @@ Tags.Disjunction): Boolean @@ Tags.Disjunction =
@@(a.unwrap || b.unwrap)
}

implicit class OptionOps[B](o: Option[B]) {
def first: Option[B] @@ Tags.First = @@(o)
}

implicit def optionMonoid[B]: Monoid[Option[B] @@ Tags.First] =
new Monoid[Option[B] @@ Tags.First] {
def empty: Option[B] @@ Tags.First = @@(Option.empty[B])
def combine(x: Option[B] @@ Tags.First, y: Option[B] @@ Tags.First): Option[B] @@ Tags.First = @@(x.unwrap.orElse(y.unwrap))
}
}
11 changes: 11 additions & 0 deletions ...les/tests/src/test/scala/higherkindness/droste/examples/foldableOperationsOnProject.scala
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Expand Up @@ -3,6 +3,7 @@ package examples

import cats.instances.list._
import cats.kernel.Eq
import cats.syntax.option._

import org.scalacheck.Properties
import org.scalacheck.Prop._
Expand Down Expand Up @@ -44,6 +45,16 @@ final class FoldableOpsChecks
case Lam(name, _) => name
} ?= List("a", "b", "c", "d", "e", "f")

property("find none") =
tru[LExpr].find {
case v @ Var(name) if name.startsWith("d") => v
} ?= Option.empty[Var]

property("find existing") =
tru[LExpr].find {
case Lam(name, _) if !name.startsWith("a") => name
} ?= "b".some

property("any") =
tru[LExpr].any {
case Var(name) => true
Expand Down