zio · adamgfraser · Sep 16, 2020 · Sep 13, 2020 · Sep 14, 2020 · Sep 14, 2020
diff --git a/core-tests/shared/src/test/scala/zio/ZIOSpec.scala b/core-tests/shared/src/test/scala/zio/ZIOSpec.scala
@@ -1208,6 +1208,14 @@ object ZIOSpec extends ZIOBaseSpec {
         assertM(task.run)(fails(isSome(equalTo(ex))))
       } @@ zioTag(errors)
     ),
+    suite("negate")(
+      testM("on true returns false") {
+        assertM(ZIO.succeed(true).negate)(equalTo(false))
+      },
+      testM("on false returns true") {
+        assertM(ZIO.succeed(false).negate)(equalTo(true))
+      }
+    ),
     suite("once")(
       testM("returns an effect that will only be executed once") {
         for {

diff --git a/core/shared/src/main/scala/zio/IO.scala b/core/shared/src/main/scala/zio/IO.scala
@@ -675,6 +675,12 @@ object IO {
    */
   val none: UIO[Option[Nothing]] = ZIO.none
 
+  /**
+   *  @see See [[zio.ZIO.not]]
+   */
+  def not[E](effect: IO[E, Boolean]): IO[E, Boolean] =
+    ZIO.not(effect)
+
   /**
    * @see See [[zio.ZIO.partition]]
    */

diff --git a/core/shared/src/main/scala/zio/RIO.scala b/core/shared/src/main/scala/zio/RIO.scala
@@ -709,6 +709,12 @@ object RIO {
    */
   val none: UIO[Option[Nothing]] = ZIO.none
 
+  /**
+   *  @see See [[zio.ZIO.not]]
+   */
+  def not[R](effect: RIO[R, Boolean]): RIO[R, Boolean] =
+    ZIO.not(effect)
+
   /**
    * @see See [[zio.ZIO.partition]]
    */

diff --git a/core/shared/src/main/scala/zio/Task.scala b/core/shared/src/main/scala/zio/Task.scala
@@ -670,6 +670,12 @@ object Task extends TaskPlatformSpecific {
    */
   val none: Task[Option[Nothing]] = ZIO.none
 
+  /**
+   *  @see See [[zio.ZIO.not]]
+   */
+  def not(effect: Task[Boolean]): Task[Boolean] =
+    ZIO.not(effect)
+
   /**
    * @see See [[zio.ZIO.partition]]
    */

diff --git a/core/shared/src/main/scala/zio/UIO.scala b/core/shared/src/main/scala/zio/UIO.scala
@@ -602,6 +602,12 @@ object UIO {
    */
   val never: UIO[Nothing] = ZIO.never
 
+  /**
+   *  @see See [[zio.ZIO.not]]
+   */
+  def not(effect: UIO[Boolean]): UIO[Boolean] =
+    ZIO.not(effect)
+
   /**
    * @see See [[zio.ZIO.raceAll]]
    */

diff --git a/core/shared/src/main/scala/zio/URIO.scala b/core/shared/src/main/scala/zio/URIO.scala
@@ -648,6 +648,12 @@ object URIO {
    */
   val none: UIO[Option[Nothing]] = ZIO.none
 
+  /**
+   *  @see See [[zio.ZIO.not]]
+   */
+  def not[R](effect: URIO[R, Boolean]): URIO[R, Boolean] =
+    ZIO.not(effect)
+
   /**
    * @see [[zio.ZIO.provide]]
    */

diff --git a/core/shared/src/main/scala/zio/ZIO.scala b/core/shared/src/main/scala/zio/ZIO.scala
@@ -909,6 +909,12 @@ sealed trait ZIO[-R, +E, +A] extends Serializable with ZIOPlatformSpecific[R, E,
   final def merge[A1 >: A](implicit ev1: E <:< A1, ev2: CanFail[E]): URIO[R, A1] =
     self.foldM(e => ZIO.succeedNow(ev1(e)), ZIO.succeedNow)
 
+  /**
+   * Returns a new effect where boolean value of this effect is negated.
+   */
+  final def negate(implicit ev: A <:< Boolean): ZIO[R, E, Boolean] =
+    map(result => !result)
+
   /**
    * Requires the option produced by this value to be `None`.
    */
@@ -3291,6 +3297,12 @@ object ZIO extends ZIOCompanionPlatformSpecific {
     if (cont(initial)) body(initial) *> loop_(inc(initial))(cont, inc)(body)
     else ZIO.unit
 
+  /**
+   * Returns a new effect where boolean value of this effect is negated.
+   */
+  def not[R, E](effect: ZIO[R, E, Boolean]): ZIO[R, E, Boolean] =
+    effect.negate
+
   /**
    * Sequentially zips the specified effects. Specialized version of mapN.
    */