Rename Inject to InjectK (#1596)

core/src/main/scala/cats/Inject.scala → core/src/main/scala/cats/InjectK.scala

@@ -4,11 +4,12 @@ import cats.arrow.FunctionK
 import cats.data.EitherK
 
 /**
- * Inject type class as described in "Data types a la carte" (Swierstra 2008).
+ * The injection type class as described in "Data types a la carte"
+ * (Swierstra 2008).
  *
  * @see [[http://www.staff.science.uu.nl/~swier004/publications/2008-jfp.pdf]]
  */
-sealed abstract class Inject[F[_], G[_]] {
+sealed abstract class InjectK[F[_], G[_]] {
   def inj: FunctionK[F, G]
 
   def prj: FunctionK[G, λ[α => Option[F[α]]]]
@@ -18,29 +19,29 @@ sealed abstract class Inject[F[_], G[_]] {
   def unapply[A](ga: G[A]): Option[F[A]] = prj(ga)
 }
 
-private[cats] sealed abstract class InjectInstances {
-  implicit def catsReflexiveInjectInstance[F[_]]: Inject[F, F] =
-    new Inject[F, F] {
+private[cats] sealed abstract class InjectKInstances {
+  implicit def catsReflexiveInjectKInstance[F[_]]: InjectK[F, F] =
+    new InjectK[F, F] {
       val inj = λ[FunctionK[F, F]](identity(_))
 
       val prj = λ[FunctionK[F, λ[α => Option[F[α]]]]](Some(_))
     }
 
-  implicit def catsLeftInjectInstance[F[_], G[_]]: Inject[F, EitherK[F, G, ?]] =
-    new Inject[F, EitherK[F, G, ?]] {
+  implicit def catsLeftInjectKInstance[F[_], G[_]]: InjectK[F, EitherK[F, G, ?]] =
+    new InjectK[F, EitherK[F, G, ?]] {
       val inj = λ[FunctionK[F, EitherK[F, G, ?]]](EitherK.leftc(_))
 
       val prj = λ[FunctionK[EitherK[F, G, ?], λ[α => Option[F[α]]]]](_.run.left.toOption)
     }
 
-  implicit def catsRightInjectInstance[F[_], G[_], H[_]](implicit I: Inject[F, G]): Inject[F, EitherK[H, G, ?]] =
-    new Inject[F, EitherK[H, G, ?]] {
+  implicit def catsRightInjectKInstance[F[_], G[_], H[_]](implicit I: InjectK[F, G]): InjectK[F, EitherK[H, G, ?]] =
+    new InjectK[F, EitherK[H, G, ?]] {
       val inj = λ[FunctionK[G, EitherK[H, G, ?]]](EitherK.rightc(_)) compose I.inj
 
       val prj = λ[FunctionK[EitherK[H, G, ?], λ[α => Option[F[α]]]]](_.run.right.toOption.flatMap(I.prj(_)))
     }
 }
 
-object Inject extends InjectInstances {
-  def apply[F[_], G[_]](implicit I: Inject[F, G]): Inject[F, G] = I
+object InjectK extends InjectKInstances {
+  def apply[F[_], G[_]](implicit I: InjectK[F, G]): InjectK[F, G] = I
 }

core/src/main/scala/cats/package.scala

@@ -10,11 +10,11 @@ package object cats {
   type ⊥ = Nothing
   type ⊤ = Any
 
-  /** [[cats.Inject]][F, G] */
-  type :<:[F[_], G[_]] = Inject[F, G]
+  /** [[cats.InjectK]][F, G] */
+  type :<:[F[_], G[_]] = InjectK[F, G]
 
-  /** [[cats.Inject]][F, G] */
-  type :≺:[F[_], G[_]] = Inject[F, G]
+  /** [[cats.InjectK]][F, G] */
+  type :≺:[F[_], G[_]] = InjectK[F, G]
 
 /**
  * Identity, encoded as `type Id[A] = A`, a convenient alias to make

docs/src/main/tut/datatypes/freemonad.md

@@ -298,15 +298,15 @@ val result: (Map[String, Any], Option[Int]) = program.foldMap(pureCompiler).run(
 ## Composing Free monads ADTs.
 
 Real world applications often time combine different algebras.
-The `Inject` type class described by Swierstra in [Data types à la carte](http://www.staff.science.uu.nl/~swier004/publications/2008-jfp.pdf)
+The injection type class described by Swierstra in [Data types à la carte](http://www.staff.science.uu.nl/~swier004/publications/2008-jfp.pdf)
 lets us compose different algebras in the context of `Free`.
 
 Let's see a trivial example of unrelated ADT's getting composed as a `EitherK` that can form a more complex program.
 
 ```tut:silent
 import cats.data.EitherK
 import cats.free.Free
-import cats.{Id, Inject, ~>}
+import cats.{Id, InjectK, ~>}
 import scala.collection.mutable.ListBuffer
 ```
 
@@ -331,22 +331,22 @@ type CatsApp[A] = EitherK[DataOp, Interact, A]
 In order to take advantage of monadic composition we use smart constructors to lift our Algebra to the `Free` context.
 
 ```tut:silent
-class Interacts[F[_]](implicit I: Inject[Interact, F]) {
+class Interacts[F[_]](implicit I: InjectK[Interact, F]) {
   def tell(msg: String): Free[F, Unit] = Free.inject[Interact, F](Tell(msg))
   def ask(prompt: String): Free[F, String] = Free.inject[Interact, F](Ask(prompt))
 }
 
 object Interacts {
-  implicit def interacts[F[_]](implicit I: Inject[Interact, F]): Interacts[F] = new Interacts[F]
+  implicit def interacts[F[_]](implicit I: InjectK[Interact, F]): Interacts[F] = new Interacts[F]
 }
 
-class DataSource[F[_]](implicit I: Inject[DataOp, F]) {
+class DataSource[F[_]](implicit I: InjectK[DataOp, F]) {
   def addCat(a: String): Free[F, Unit] = Free.inject[DataOp, F](AddCat(a))
   def getAllCats: Free[F, List[String]] = Free.inject[DataOp, F](GetAllCats())
 }
 
 object DataSource {
-  implicit def dataSource[F[_]](implicit I: Inject[DataOp, F]): DataSource[F] = new DataSource[F]
+  implicit def dataSource[F[_]](implicit I: InjectK[DataOp, F]): DataSource[F] = new DataSource[F]
 }
 ```
 
@@ -495,9 +495,9 @@ right-associated structure not subject to quadratic complexity.
 
 ## FreeT
 
-Often times we want to interleave the syntax tree when building a Free monad 
-with some other effect not declared as part of the ADT. 
-FreeT solves this problem by allowing us to mix building steps of the AST 
+Often times we want to interleave the syntax tree when building a Free monad
+with some other effect not declared as part of the ADT.
+FreeT solves this problem by allowing us to mix building steps of the AST
 with calling action in other base monad.
 
 In the following example a basic console application is shown.
@@ -521,7 +521,7 @@ type TeletypeT[M[_], A] = FreeT[Teletype, M, A]
 type Log = List[String]
 
 /** Smart constructors, notice we are abstracting over any MonadState instance
- *  to potentially support other types beside State 
+ *  to potentially support other types beside State
  */
 class TeletypeOps[M[_]](implicit MS : MonadState[M, Log]) {
   def writeLine(line : String) : TeletypeT[M, Unit] =
@@ -543,11 +543,11 @@ def program(implicit TO : TeletypeOps[TeletypeState]) : TeletypeT[TeletypeState,
 	userSaid <- TO.readLine("what's up?!")
 	_ <- TO.log(s"user said : $userSaid")
 	_ <- TO.writeLine("thanks, see you soon!")
-  } yield () 
+  } yield ()
 }
 
 def interpreter = new (Teletype ~> TeletypeState) {
-  def apply[A](fa : Teletype[A]) : TeletypeState[A] = {  
+  def apply[A](fa : Teletype[A]) : TeletypeState[A] = {
 	fa match {
 	  case ReadLine(prompt) =>
 		println(prompt)

docs/src/main/tut/typeclasses/symbols.md

@@ -1,6 +1,6 @@
 #Symbols
 
-Below is a list of symbols used in cats.  
+Below is a list of symbols used in cats.
 
 The `~>`, `⊥` and `⊤` symbols can be imported with `import cats._`.
 
@@ -25,7 +25,7 @@ A scaladoc generated list is also available on the [Scaladoc symbols page](http:
 | `x |+| y`  | Semigroup combine      | [`Semigroup[A]`]({{ site.sources }}/kernel/src/main/scala/cats/kernel/Semigroup.scala)      | `combine(x: A, y: A): A`               |
 | `x <+> y`  | SemigroupK combine     | [`SemigroupK[F[_]]`]({{ site.sources }}/core/src/main/scala/cats/SemigroupK.scala)          | `combineK(x: F[A], y: F[A]): F[A]`     |
 | `F ~> G`   | natural transformation | [`FunctionK[F[_], G[_]]`]({{ site.sources }}/core/src/main/scala/cats/arrow/FunctionK.scala)| `FunctionK` alias                      |
-| `F :<: G`  | inject                 | [`Inject[F[_], G[_]]`]({{ site.sources }}/free/src/main/scala/cats/free/package.scala)      | `Inject` alias                         |
-| `F :≺: G`  | inject                 | [`Inject[F[_], G[_]]`]({{ site.sources }}/free/src/main/scala/cats/free/package.scala)      | `Inject` alias                         |
+| `F :<: G`  | inject                 | [`InjectK[F[_], G[_]]`]({{ site.sources }}/free/src/main/scala/cats/free/package.scala)     | `InjectK` alias                         |
+| `F :≺: G`  | inject                 | [`InjectK[F[_], G[_]]`]({{ site.sources }}/free/src/main/scala/cats/free/package.scala)     | `InjectK` alias                         |
 | `⊥`        | bottom                 | [N/A]({{ site.sources }}/core/src/main/scala/cats/package.scala)                            | `Nothing`                              |
 | `⊤`        | top                    | [N/A]({{ site.sources }}/core/src/main/scala/cats/package.scala)                            | `Any`                                  |

free/src/main/scala/cats/free/Free.scala

@@ -140,7 +140,7 @@ sealed abstract class Free[S[_], A] extends Product with Serializable {
     }(Free.catsFreeMonadForFree)
 
   /**
-   * Lift into `G` (typically a `EitherK`) given `Inject`. Analogous
+   * Lift into `G` (typically a `EitherK`) given `InjectK`. Analogous
    * to `Free.inject` but lifts programs rather than constructors.
    *
    *{{{
@@ -154,7 +154,7 @@ sealed abstract class Free[S[_], A] extends Product with Serializable {
    *res4: cats.free.Free[Lo,String] = Free(...)
    *}}}
    */
-  final def inject[G[_]](implicit ev: Inject[S, G]): Free[G, A] =
+  final def inject[G[_]](implicit ev: InjectK[S, G]): Free[G, A] =
     compile(λ[S ~> G](ev.inj(_)))
 
   override def toString: String =
@@ -209,28 +209,28 @@ object Free {
     λ[FunctionK[Free[F, ?], M]](f => f.foldMap(fk))
 
   /**
-   * This method is used to defer the application of an Inject[F, G]
+   * This method is used to defer the application of an InjectK[F, G]
    * instance. The actual work happens in
-   * `FreeInjectPartiallyApplied#apply`.
+   * `FreeInjectKPartiallyApplied#apply`.
    *
    * This method exists to allow the `F` and `G` parameters to be
    * bound independently of the `A` parameter below.
    */
-  def inject[F[_], G[_]]: FreeInjectPartiallyApplied[F, G] =
-    new FreeInjectPartiallyApplied
+  def inject[F[_], G[_]]: FreeInjectKPartiallyApplied[F, G] =
+    new FreeInjectKPartiallyApplied
 
   /**
    * Pre-application of an injection to a `F[A]` value.
    */
-  final class FreeInjectPartiallyApplied[F[_], G[_]] private[free] {
-    def apply[A](fa: F[A])(implicit I: Inject[F, G]): Free[G, A] =
+  final class FreeInjectKPartiallyApplied[F[_], G[_]] private[free] {
+    def apply[A](fa: F[A])(implicit I: InjectK[F, G]): Free[G, A] =
       Free.liftF(I.inj(fa))
   }
 
-  def injectRoll[F[_], G[_], A](ga: G[Free[F, A]])(implicit I: Inject[G, F]): Free[F, A] =
+  def injectRoll[F[_], G[_], A](ga: G[Free[F, A]])(implicit I: InjectK[G, F]): Free[F, A] =
     Free.roll(I.inj(ga))
 
-  def match_[F[_], G[_], A](fa: Free[F, A])(implicit F: Functor[F], I: Inject[G, F]): Option[G[Free[F, A]]] =
+  def match_[F[_], G[_], A](fa: Free[F, A])(implicit F: Functor[F], I: InjectK[G, F]): Option[G[Free[F, A]]] =
     fa.resume.fold(I.prj(_), _ => None)
 
   /**

tests/src/test/scala/cats/tests/InjectTests.scala → tests/src/test/scala/cats/tests/InjectKTests.scala

@@ -4,7 +4,7 @@ import cats.data.EitherK
 import cats.tests.CatsSuite
 import org.scalacheck._
 
-class InjectTests extends CatsSuite {
+class InjectKTests extends CatsSuite {
 
   sealed trait Test1Algebra[A]
 
@@ -52,8 +52,8 @@ class InjectTests extends CatsSuite {
       } yield x + y
 
     forAll { (x: Int, y: Int) =>
-      val expr1: T[Int] = Inject[Test1Algebra, T].inj(Test1(x, _ + 1))
-      val expr2: T[Int] = Inject[Test2Algebra, T].inj(Test2(y, _ * 2))
+      val expr1: T[Int] = InjectK[Test1Algebra, T].inj(Test1(x, _ + 1))
+      val expr2: T[Int] = InjectK[Test2Algebra, T].inj(Test2(y, _ * 2))
       val res = distr[T, Int](expr1, expr2)
       res should ===(Some(x + y))
     }
@@ -71,29 +71,29 @@ class InjectTests extends CatsSuite {
       } yield x + y
 
     forAll { (x: Int, y: Int) =>
-      val expr1: T[Int] = Inject[Test1Algebra, T].apply(Test1(x, _ + 1))
-      val expr2: T[Int] = Inject[Test2Algebra, T].apply(Test2(y, _ * 2))
+      val expr1: T[Int] = InjectK[Test1Algebra, T].apply(Test1(x, _ + 1))
+      val expr2: T[Int] = InjectK[Test2Algebra, T].apply(Test2(y, _ * 2))
       val res = distr[T, Int](expr1, expr2)
       res should ===(Some(x + y))
     }
   }
 
   test("apply in left") {
     forAll { (y: Test1Algebra[Int]) =>
-      Inject[Test1Algebra, T].inj(y) == EitherK(Left(y)) should ===(true)
+      InjectK[Test1Algebra, T].inj(y) == EitherK(Left(y)) should ===(true)
     }
   }
 
   test("apply in right") {
     forAll { (y: Test2Algebra[Int]) =>
-      Inject[Test2Algebra, T].inj(y) == EitherK(Right(y)) should ===(true)
+      InjectK[Test2Algebra, T].inj(y) == EitherK(Right(y)) should ===(true)
     }
   }
 
   test("null identity") {
     val listIntNull = null.asInstanceOf[List[Int]]
-    Inject.catsReflexiveInjectInstance[List].inj[Int](listIntNull) should ===(listIntNull)
-    Inject.catsReflexiveInjectInstance[List].prj[Int](listIntNull) should ===(Some(listIntNull))
+    InjectK.catsReflexiveInjectKInstance[List].inj[Int](listIntNull) should ===(listIntNull)
+    InjectK.catsReflexiveInjectKInstance[List].prj[Int](listIntNull) should ===(Some(listIntNull))
   }
 
 }