Bring Ring-like structures to ZIO Prelude (#351)

build.sbt

@@ -1,6 +1,7 @@
 import BuildHelper._
 
 Global / onChangedBuildSource := ReloadOnSourceChanges
+Global / concurrentRestrictions += Tags.limit(NativeTags.Link, 1)
 
 inThisBuild(
   List(

core-tests/shared/src/test/scala/zio/prelude/CoherentSpec.scala

@@ -45,9 +45,9 @@ object CoherentSpec extends ZIOBaseSpec {
       test("EqualInverse") {
         val instance = implicitly[EqualInverse[Sum[Int]]]
         assert(Sum(42).inverse(Sum(20)))(equalTo(Sum(22))) &&
-        assert(Sum(2).multiply(5))(equalTo(Sum(10))) &&
-        assert(Sum(2).multiply(0))(equalTo(Sum(0))) &&
-        assert(Sum(2).multiply(-5))(equalTo(Sum(-10))) &&
+        assert(Sum(2).multiplyBy(5))(equalTo(Sum(10))) &&
+        assert(Sum(2).multiplyBy(0))(equalTo(Sum(0))) &&
+        assert(Sum(2).multiplyBy(-5))(equalTo(Sum(-10))) &&
         assert(instance.multiplyOption(5)(Sum(2)))(equalTo[Option[Sum[Int]]](Some(Sum(10)))) &&
         assert(instance.multiplyOption(0)(Sum(2)))(equalTo[Option[Sum[Int]]](Some(Sum(0)))) &&
         assert(instance.multiplyOption(-5)(Sum(2)))(equalTo[Option[Sum[Int]]](Some(Sum(-10))))

core-tests/shared/src/test/scala/zio/prelude/PartialInverseSpec.scala

@@ -0,0 +1,28 @@
+package zio.prelude
+
+import zio.prelude.laws._
+import zio.prelude.newtypes.Prod
+import zio.test._
+import zio.test.laws._
+
+object PartialInverseSpec extends ZIOBaseSpec {
+
+  private implicit val DoubleEqual: Equal[Double] = Equal.DoubleEqualWithEpsilon()
+  private implicit val FloatEqual: Equal[Float]   = Equal.FloatEqualWithEpsilon()
+
+  def spec: Spec[Environment, Any] =
+    suite("PartialInverseSpec")(
+      suite("laws")(
+        test("BigDecimal prod")(
+          checkAllLaws(PartialInverseLaws)(Gen.bigDecimal(BigDecimal(-10), BigDecimal(10)).map(Prod(_)))
+        ),
+        test("byte prod")(checkAllLaws(PartialInverseLaws)(Gen.byte.map(Prod(_)))),
+        test("char prod")(checkAllLaws(PartialInverseLaws)(Gen.char.map(Prod(_)))),
+        test("double prod")(checkAllLaws(PartialInverseLaws)(Gen.double.map(Prod(_)))),
+        test("float prod")(checkAllLaws(PartialInverseLaws)(Gen.float.map(Prod(_)))),
+        test("int prod")(checkAllLaws(PartialInverseLaws)(Gen.int.map(Prod(_)))),
+        test("long prod")(checkAllLaws(PartialInverseLaws)(Gen.long.map(Prod(_)))),
+        test("short prod")(checkAllLaws(PartialInverseLaws)(Gen.short.map(Prod(_))))
+      )
+    )
+}

core/shared/src/main/scala/zio/prelude/Associative.scala

@@ -183,19 +183,25 @@ object Associative extends AssociativeLowPriority {
     }
 
   /**
-   * The `Commutative`, `Idempotent` instance for the product of `BigDecimal` values
+   * The `Commutative`, `PartialInverse` instance for the product of `BigDecimal` values
    */
-  implicit val BigDecimalProdCommutativeIdempotent: Commutative[Prod[BigDecimal]] with Idempotent[Prod[BigDecimal]] =
-    new Commutative[Prod[BigDecimal]] with Idempotent[Prod[BigDecimal]] {
-      override def combine(l: => Prod[BigDecimal], r: => Prod[BigDecimal]): Prod[BigDecimal] = Prod(l * r)
+  implicit val BigDecimalProdCommutativePartialInverse
+    : Commutative[Prod[BigDecimal]] with PartialInverse[Prod[BigDecimal]] =
+    new Commutative[Prod[BigDecimal]] with PartialInverse[Prod[BigDecimal]] {
+      def combine(l: => Prod[BigDecimal], r: => Prod[BigDecimal]): Prod[BigDecimal]               = Prod(l * r)
+      val identity: Prod[BigDecimal]                                                              = Prod(BigDecimal(1))
+      def inverseOption(l: => Prod[BigDecimal], r: => Prod[BigDecimal]): Option[Prod[BigDecimal]] =
+        if (r != BigDecimal(0)) Some(Prod(l / r)) else None
     }
 
   /**
    * The `Commutative`, `Idempotent` instance for the sum of `BigDecimal` values
    */
-  implicit val BigDecimalSumCommutativeIdempotent: Commutative[Sum[BigDecimal]] with Idempotent[Sum[BigDecimal]] =
-    new Commutative[Sum[BigDecimal]] with Idempotent[Sum[BigDecimal]] {
-      override def combine(l: => Sum[BigDecimal], r: => Sum[BigDecimal]): Sum[BigDecimal] = Sum(l + r)
+  implicit val BigDecimalSumCommutativeInverse: Commutative[Sum[BigDecimal]] with Inverse[Sum[BigDecimal]] =
+    new Commutative[Sum[BigDecimal]] with Inverse[Sum[BigDecimal]] {
+      def combine(l: => Sum[BigDecimal], r: => Sum[BigDecimal]): Sum[BigDecimal] = Sum(l + r)
+      val identity: Sum[BigDecimal]                                              = Sum(BigDecimal(0))
+      def inverse(l: => Sum[BigDecimal], r: => Sum[BigDecimal]): Sum[BigDecimal] = Sum(l - r)
     }
 
   /**
@@ -255,13 +261,15 @@ object Associative extends AssociativeLowPriority {
     }
 
   /**
-   * The `Commutative` and `Identity` instance for the product of `Byte`
+   * The `Commutative` and `PartialInverse` instance for the product of `Byte`
    * values.
    */
-  implicit val ByteProdCommutativeIdentity: Commutative[Prod[Byte]] with Identity[Prod[Byte]] =
-    new Commutative[Prod[Byte]] with Identity[Prod[Byte]] {
-      def combine(l: => Prod[Byte], r: => Prod[Byte]): Prod[Byte] = Prod((l * r).toByte)
-      val identity: Prod[Byte]                                    = Prod(1)
+  implicit val ByteProdCommutativePartialInverse: Commutative[Prod[Byte]] with PartialInverse[Prod[Byte]] =
+    new Commutative[Prod[Byte]] with PartialInverse[Prod[Byte]] {
+      def combine(l: => Prod[Byte], r: => Prod[Byte]): Prod[Byte]               = Prod((l * r).toByte)
+      val identity: Prod[Byte]                                                  = Prod(1)
+      def inverseOption(l: => Prod[Byte], r: => Prod[Byte]): Option[Prod[Byte]] =
+        if (r != 0) Some(Prod((l / r).toByte)) else None
     }
 
   /**
@@ -291,13 +299,15 @@ object Associative extends AssociativeLowPriority {
     }
 
   /**
-   * The `Commutative` and `Identity` instance for the product of `Char`
+   * The `Commutative` and `PartialInverse` instance for the product of `Char`
    * values.
    */
-  implicit val CharProdCommutativeIdentity: Commutative[Prod[Char]] with Identity[Prod[Char]] =
-    new Commutative[Prod[Char]] with Identity[Prod[Char]] {
-      def combine(l: => Prod[Char], r: => Prod[Char]): Prod[Char] = Prod((l * r).toChar)
-      val identity: Prod[Char]                                    = Prod(1)
+  implicit val CharProdCommutativePartialInverse: Commutative[Prod[Char]] with PartialInverse[Prod[Char]] =
+    new Commutative[Prod[Char]] with PartialInverse[Prod[Char]] {
+      def combine(l: => Prod[Char], r: => Prod[Char]): Prod[Char]                        = Prod((l * r).toChar)
+      val identity: Prod[Char]                                                           = Prod(1)
+      override def inverseOption(l: => Prod[Char], r: => Prod[Char]): Option[Prod[Char]] =
+        if (r != 0) Some(Prod((l / r).toChar)) else None
     }
 
   /**
@@ -369,13 +379,15 @@ object Associative extends AssociativeLowPriority {
     }
 
   /**
-   * The `Commutative` and `Identity` instance for the product of `Double`
+   * The `Commutative` and `PartialInverse` instance for the product of `Double`
    * values.
    */
-  implicit val DoubleProdCommutativeIdentity: Commutative[Prod[Double]] with Identity[Prod[Double]] =
-    new Commutative[Prod[Double]] with Identity[Prod[Double]] {
-      def combine(l: => Prod[Double], r: => Prod[Double]): Prod[Double] = Prod(l * r)
-      val identity: Prod[Double]                                        = Prod(1)
+  implicit val DoubleProdCommutativePartialInverse: Commutative[Prod[Double]] with PartialInverse[Prod[Double]] =
+    new Commutative[Prod[Double]] with PartialInverse[Prod[Double]] {
+      def combine(l: => Prod[Double], r: => Prod[Double]): Prod[Double]               = Prod(l * r)
+      val identity: Prod[Double]                                                      = Prod(1)
+      def inverseOption(l: => Prod[Double], r: => Prod[Double]): Option[Prod[Double]] =
+        if (r != 0) Some(Prod(l / r)) else None
     }
 
   /**
@@ -431,13 +443,15 @@ object Associative extends AssociativeLowPriority {
     }
 
   /**
-   * The `Commutative` and `Identity` instance for the product of `Float`
+   * The `Commutative` and `PartialInverse` instance for the product of `Float`
    * values.
    */
-  implicit val FloatProdCommutativeIdentity: Commutative[Prod[Float]] with Identity[Prod[Float]] =
-    new Commutative[Prod[Float]] with Identity[Prod[Float]] {
-      def combine(l: => Prod[Float], r: => Prod[Float]): Prod[Float] = Prod(l * r)
-      val identity: Prod[Float]                                      = Prod(1)
+  implicit val FloatProdCommutativePartialInverse: Commutative[Prod[Float]] with PartialInverse[Prod[Float]] =
+    new Commutative[Prod[Float]] with PartialInverse[Prod[Float]] {
+      def combine(l: => Prod[Float], r: => Prod[Float]): Prod[Float]               = Prod(l * r)
+      val identity: Prod[Float]                                                    = Prod(1)
+      def inverseOption(l: => Prod[Float], r: => Prod[Float]): Option[Prod[Float]] =
+        if (r != 0) Some(Prod(l / r)) else None
     }
 
   /**
@@ -501,13 +515,15 @@ object Associative extends AssociativeLowPriority {
     }
 
   /**
-   * The `Commutative` and `Identity` instance for the product of `Long`
+   * The `Commutative` and `PartialInverse` instance for the product of `Long`
    * values.
    */
-  implicit val LongProdCommutativeIdentity: Commutative[Prod[Long]] with Identity[Prod[Long]] =
-    new Commutative[Prod[Long]] with Identity[Prod[Long]] {
-      def combine(l: => Prod[Long], r: => Prod[Long]): Prod[Long] = Prod(l * r)
-      val identity: Prod[Long]                                    = Prod(1)
+  implicit val LongProdCommutativePartialInverse: Commutative[Prod[Long]] with PartialInverse[Prod[Long]] =
+    new Commutative[Prod[Long]] with PartialInverse[Prod[Long]] {
+      def combine(l: => Prod[Long], r: => Prod[Long]): Prod[Long]               = Prod(l * r)
+      val identity: Prod[Long]                                                  = Prod(1)
+      def inverseOption(l: => Prod[Long], r: => Prod[Long]): Option[Prod[Long]] =
+        if (r != 0) Some(Prod(l / r)) else None
     }
 
   /**
@@ -587,6 +603,21 @@ object Associative extends AssociativeLowPriority {
       }
     )
 
+  implicit def ParSeqProdIdentity[A]: Identity[Prod[ParSeq[Unit, A]]] = new Identity[Prod[ParSeq[Unit, A]]] {
+    def identity: Prod[ParSeq[Unit, A]]                                                          =
+      Prod(ParSeq.empty)
+    def combine(l: => Prod[ParSeq[Unit, A]], r: => Prod[ParSeq[Unit, A]]): Prod[ParSeq[Unit, A]] =
+      Prod(Prod.unwrap(l) ++ Prod.unwrap(r))
+  }
+
+  implicit def ParSeqSumCommutativeIdentity[A]: Commutative[Sum[ParSeq[Unit, A]]] with Identity[Sum[ParSeq[Unit, A]]] =
+    new Commutative[Sum[ParSeq[Unit, A]]] with Identity[Sum[ParSeq[Unit, A]]] {
+      def identity: Sum[ParSeq[Unit, A]]                                                        =
+        Sum(ParSeq.empty)
+      def combine(l: => Sum[ParSeq[Unit, A]], r: => Sum[ParSeq[Unit, A]]): Sum[ParSeq[Unit, A]] =
+        Sum(Sum.unwrap(l) && Sum.unwrap(r))
+    }
+
   /**
    * The `Commutative` and `Idempotent` instance for the intersection of `Set[A]` values.
    */
@@ -623,19 +654,21 @@ object Associative extends AssociativeLowPriority {
     }
 
   /**
-   * The `Commutative` and `Identity` instance for the product of `Short`
+   * The `Commutative` and `PartialInverse` instance for the product of `Short`
    * values.
    */
-  implicit val ShortProdCommutativeIdentity: Commutative[Prod[Short]] with Identity[Prod[Short]] =
-    new Commutative[Prod[Short]] with Identity[Prod[Short]] {
-      def combine(l: => Prod[Short], r: => Prod[Short]): Prod[Short] = Prod((l * r).toShort)
-      val identity: Prod[Short]                                      = Prod(1)
+  implicit val ShortProdCommutativePartialInverse: Commutative[Prod[Short]] with PartialInverse[Prod[Short]] =
+    new Commutative[Prod[Short]] with PartialInverse[Prod[Short]] {
+      def combine(l: => Prod[Short], r: => Prod[Short]): Prod[Short]               = Prod((l * r).toShort)
+      val identity: Prod[Short]                                                    = Prod(1)
+      def inverseOption(l: => Prod[Short], r: => Prod[Short]): Option[Prod[Short]] =
+        if (r != 0) Some(Prod((l / r).toShort)) else None
     }
 
   /**
-   * The `Commutative` and `Identity` instance for the sum of `Short` values.
+   * The `Commutative` and `Inverse` instance for the sum of `Short` values.
    */
-  implicit val ShortSumCommutativeIdentity: Commutative[Sum[Short]] with Inverse[Sum[Short]] =
+  implicit val ShortSumCommutativeInverse: Commutative[Sum[Short]] with Inverse[Sum[Short]] =
     new Commutative[Sum[Short]] with Inverse[Sum[Short]] {
       def combine(l: => Sum[Short], r: => Sum[Short]): Sum[Short] = Sum((l + r).toShort)
       val identity: Sum[Short]                                    = Sum(0)
@@ -1388,17 +1421,44 @@ object Associative extends AssociativeLowPriority {
    */
   implicit def VectorIdentity[A]: Identity[Vector[A]] =
     Identity.make(Vector.empty, _ ++ _)
+
+  implicit def zioCauseProdIdentity[A]: Identity[Prod[zio.Cause[A]]] = new Identity[Prod[zio.Cause[A]]] {
+    def identity: Prod[zio.Cause[A]]                                                    =
+      Prod(zio.Cause.empty)
+    def combine(l: => Prod[zio.Cause[A]], r: => Prod[zio.Cause[A]]): Prod[zio.Cause[A]] =
+      Prod(Prod.unwrap(l) ++ Prod.unwrap(r))
+  }
+
+  implicit def zioCauseSumCommutativeIdentity[A]: Commutative[Sum[zio.Cause[A]]] with Identity[Sum[zio.Cause[A]]] =
+    new Commutative[Sum[zio.Cause[A]]] with Identity[Sum[zio.Cause[A]]] {
+      def identity: Sum[zio.Cause[A]]                                                  =
+        Sum(zio.Cause.empty)
+      def combine(l: => Sum[zio.Cause[A]], r: => Sum[zio.Cause[A]]): Sum[zio.Cause[A]] =
+        Sum(Sum.unwrap(l) && Sum.unwrap(r))
+    }
 }
 
 trait AssociativeLowPriority {
 
+  implicit def FxCauseProdAssociative[A]: Associative[Prod[fx.Cause[A]]] = new Associative[Prod[fx.Cause[A]]] {
+    def combine(l: => Prod[fx.Cause[A]], r: => Prod[fx.Cause[A]]): Prod[fx.Cause[A]] =
+      Prod(Prod.unwrap(l) ++ Prod.unwrap(r))
+  }
+
+  implicit def FxCauseSumCommutative[A]: Commutative[Sum[fx.Cause[A]]] = new Commutative[Sum[fx.Cause[A]]] {
+    def combine(l: => Sum[fx.Cause[A]], r: => Sum[fx.Cause[A]]): Sum[fx.Cause[A]] =
+      Sum(Sum.unwrap(l) && Sum.unwrap(r))
+  }
+
   /**
-   * The `Commutative` and `Identity` instance for the product of `Int` values.
+   * The `Commutative` and `PartialInverse` instance for the product of `Int` values.
    */
-  implicit val IntProdCommutativeIdentity: Commutative[Prod[Int]] with Identity[Prod[Int]] =
-    new Commutative[Prod[Int]] with Identity[Prod[Int]] {
-      def combine(l: => Prod[Int], r: => Prod[Int]): Prod[Int] = Prod(l * r)
-      val identity: Prod[Int]                                  = Prod(1)
+  implicit val IntProdCommutativePartialInverse: Commutative[Prod[Int]] with PartialInverse[Prod[Int]] =
+    new Commutative[Prod[Int]] with PartialInverse[Prod[Int]] {
+      def combine(l: => Prod[Int], r: => Prod[Int]): Prod[Int]               = Prod(l * r)
+      val identity: Prod[Int]                                                = Prod(1)
+      def inverseOption(l: => Prod[Int], r: => Prod[Int]): Option[Prod[Int]] =
+        if (r != 0) Some(Prod(l / r)) else None
     }
 
   /**

core/shared/src/main/scala/zio/prelude/Inverse.scala

@@ -34,10 +34,13 @@ import scala.annotation.tailrec
  * natural numbers, since subtracting a number from itself always returns
  * zero.
  */
-trait Inverse[A] extends Identity[A] {
+trait Inverse[A] extends PartialInverse[A] {
+
   def inverse(l: => A, r: => A): A
 
-  def multiply(n: Int)(a: A): A = {
+  final override def inverseOption(l: => A, r: => A): Some[A] = Some(inverse(l, r))
+
+  def multiplyBy(n: Int)(a: A): A = {
     @tailrec
     def multiplyHelper(res: A, n: Int): A =
       if (n == 0) res
@@ -46,8 +49,8 @@ trait Inverse[A] extends Identity[A] {
     multiplyHelper(identity, n)
   }
 
-  override def multiplyOption(n: Int)(a: A): Some[A] =
-    Some(multiply(n)(a))
+  final override def multiplyOption(n: Int)(a: A): Some[A] =
+    Some(multiplyBy(n)(a))
 }
 
 object Inverse {
@@ -903,7 +906,7 @@ trait InverseSyntax {
     /**
      * Multiplies value 'n' times
      */
-    def multiply(n: Int)(implicit inverse: Inverse[A]): A =
-      inverse.multiply(n)(l)
+    def multiplyBy(n: Int)(implicit inverse: Inverse[A]): A =
+      inverse.multiplyBy(n)(l)
   }
 }