Merge pull request #2552 from flomebul/compound-types

Add code tabs for _tour/compound-types

Author: bishabosha

_tour/compound-types.md

@@ -1,6 +1,6 @@
 ---
 layout: tour
-title: Compound Types
+title: Intersection Types, aka Compound Types
 partof: scala-tour
 
 num: 26
@@ -10,42 +10,86 @@ previous-page: abstract-type-members
 redirect_from: "/tutorials/tour/compound-types.html"
 ---
 
-Sometimes it is necessary to express that the type of an object is a subtype of several other types. In Scala this can be expressed with the help of *compound types*, which are intersections of object types.
+Sometimes it is necessary to express that the type of an object is a subtype of several other types.
+
+In Scala this can be expressed with the help of *intersection types*, (or *compound types* in
+Scala 2) which are types that behave like any part of the intersection.
 
 Suppose we have two traits `Cloneable` and `Resetable`:
 
+{% tabs compound-types_1 class=tabs-scala-version %}
+{% tab 'Scala 2' for=compound-types_1 %}
 ```scala mdoc
 trait Cloneable extends java.lang.Cloneable {
-  override def clone(): Cloneable = {
+  override def clone(): Cloneable = { // makes clone public
     super.clone().asInstanceOf[Cloneable]
   }
 }
 trait Resetable {
   def reset: Unit
 }
 ```
+{% endtab %}
+{% tab 'Scala 3' for=compound-types_1 %}
+```scala
+trait Cloneable extends java.lang.Cloneable:
+  override def clone(): Cloneable =  // makes clone public
+    super.clone().asInstanceOf[Cloneable]
+trait Resetable:
+  def reset: Unit
+```
+{% endtab %}
+{% endtabs %}
 
 Now suppose we want to write a function `cloneAndReset` which takes an object, clones it and resets the original object:
 
-```
+{% tabs compound-types_2 class=tabs-scala-version %}
+{% tab 'Scala 2' for=compound-types_2 %}
+```scala mdoc:fail
 def cloneAndReset(obj: ?): Cloneable = {
   val cloned = obj.clone()
   obj.reset
   cloned
 }
 ```
+{% endtab %}
+{% tab 'Scala 3' for=compound-types_2 %}
+```scala
+def cloneAndReset(obj: ?): Cloneable =
+  val cloned = obj.clone()
+  obj.reset
+  cloned
+```
+{% endtab %}
+{% endtabs %}
 
-The question arises what the type of the parameter `obj` is. If it's `Cloneable` then the object can be `clone`d, but not `reset`; if it's `Resetable` we can `reset` it, but there is no `clone` operation. To avoid type casts in such a situation, we can specify the type of `obj` to be both `Cloneable` and `Resetable`. This compound type is written like this in Scala: `Cloneable with Resetable`.
+The question arises what the type of the parameter `obj` is. If it's `Cloneable` then the object can be `clone`d, but not `reset`; if it's `Resetable` we can `reset` it, but there is no `clone` operation. To avoid type casts in such a situation, we can specify the type of `obj` to be both `Cloneable` and `Resetable`.
+{% tabs compound-types_3 class=tabs-scala-version %}
+{% tab 'Scala 2' for=compound-types_3 %}
+This compound type is written in Scala as `Cloneable with Resetable`.
 
 Here's the updated function:
-
-```
+```scala mdoc:fail
 def cloneAndReset(obj: Cloneable with Resetable): Cloneable = {
   //...
 }
 ```
+Note that you can have more than two types: `A with B with C with ...`.
+This means the same as thing as `(...(A with B) with C) with ... )`
+{% endtab %}
+{% tab 'Scala 3' for=compound-types_3 %}
+This intersection type is written in Scala as `Cloneable & Resetable`.
 
-Compound types can consist of several object types and they may have a single refinement which can be used to narrow the signature of existing object members.
-The general form is: `A with B with C ... { refinement }`
+Here's the updated function:
+```scala
+def cloneAndReset(obj: Cloneable & Resetable): Cloneable = {
+  //...
+}
+```
+<!-- Compound types can consist of several object types and they may have a single refinement which can be used to narrow the signature of existing object members. -->
+Note that you can have more than two types: `A & B & C & ...`.
+And `&` is associative, so parentheses can be added around any part without changing the meaning.
+{% endtab %}
+{% endtabs %}
 
-An example for the use of refinements is given on the page about [class composition with mixins](mixin-class-composition.html).
+<!-- An example for the use of refinements is given on the page about [class composition with mixins](mixin-class-composition.html). -->