Updated pages to be 'Scala 3 Only'

Author: alvinj

_overviews/scala3-book/ca-context-bounds.md

@@ -7,6 +7,7 @@ num: 61
 previous-page: ca-given-using-clauses
 next-page: ca-given-imports
 ---
+<span class="tag tag-inline">Scala 3 only</span>
 
 
 {% comment %}
@@ -22,29 +23,54 @@ In that case you don’t have to define a parameter name, and can just provide t
 
 For example, this `maximum` method takes a _context parameter_ of type `Ord`, only to pass it on as an argument to `max`:
 
+{% tabs context-bounds-max-named-param %}
+
+{% tab 'Scala 3 Only' %}
+
 ```scala
 def maximum[A](xs: List[A])(using ord: Ord[A]): A =
   xs.reduceLeft(max(ord))
 ```
 
+{% endtab %}
+
+{% endtabs %}
+
 In that code the parameter name `ord` isn’t actually required; it can be passed on as an inferred argument to `max`, so you just state that `maximum` uses the type `Ord[A]` without giving it a name:
 
+{% tabs context-bounds-no-param-name %}
+
+{% tab 'Scala 3 Only' %}
+
 ```scala
 def maximum[A](xs: List[A])(using Ord[A]): A =
   xs.reduceLeft(max)
 ```
 
+{% endtab %}
+
+{% endtabs %}
+
 
 ## Context bounds
 
 Given that background, a _context bound_ is a shorthand syntax for expressing the pattern of, “a context parameter that depends on a type parameter.”
 
 Using a context bound, the `maximum` method can be written like this:
 
+{% tabs context-bounds-max-rewritten %}
+
+{% tab 'Scala 3 Only' %}
+
 ```scala
 def maximum[A: Ord](xs: List[A]): A = xs.reduceLeft(max)
 ```
 
+{% endtab %}
+
+{% endtabs %}
+
+
 A bound like `: Ord` on a type parameter `A` of a method or class indicates a context parameter with `Ord[A]`.
 
 For more information about context bounds, see the [“What are context bounds?”](https://docs.scala-lang.org/tutorials/FAQ/context-bounds.html) section of the Scala FAQ.

_overviews/scala3-book/ca-given-imports.md

@@ -7,11 +7,16 @@ num: 62
 previous-page: ca-context-bounds
 next-page: ca-type-classes
 ---
+<span class="tag tag-inline">Scala 3 only</span>
 
 
 To make it more clear where givens in the current scope are coming from, a special form of the `import` statement is used to import `given` instances.
 The basic form is shown in this example:
 
+{% tabs given-imports-basic-form %}
+
+{% tab 'Scala 3 Only' %}
+
 ```scala
 object A:
   class TC
@@ -23,15 +28,27 @@ object B:
   import A.given   // import the given instance
 ```
 
+{% endtab %}
+
+{% endtabs %}
+
 In this code the `import A.*` clause of object `B` imports all members of `A` *except* the `given` instance, `tc`.
 Conversely, the second import, `import A.given`, imports *only* that `given` instance.
 The two `import` clauses can also be merged into one:
 
+{% tabs given-imports-merged %}
+
+{% tab 'Scala 3 Only' %}
+
 ```scala
 object B:
   import A.{given, *}
 ```
 
+{% endtab %}
+
+{% endtabs %}
+
 
 ## Discussion
 

_overviews/scala3-book/ca-multiversal-equality.md

@@ -7,6 +7,7 @@ num: 64
 previous-page: ca-type-classes
 next-page: ca-implicit-conversions
 ---
+<span class="tag tag-inline">Scala 3 only</span>
 
 
 Previously, Scala had *universal equality*: Two values of any types could be compared with each other using `==` and `!=`.
@@ -44,6 +45,10 @@ d == c  // false, but it compiles
 But with Scala 3 you can disable such comparisons.
 By (a) importing `scala.language.strictEquality` or (b) using the `-language:strictEquality` compiler flag, this comparison no longer compiles:
 
+{% tabs multiversal-equality-strictEquality %}
+
+{% tab 'Scala 3 Only' %}
+
 ```scala
 import scala.language.strictEquality
 
@@ -55,25 +60,45 @@ println(rover == fido)   // compiler error
 // Values of types Dog and Dog cannot be compared with == or !=
 ```
 
+{% endtab %}
+
+{% endtabs %}
+
 
 ## Enabling comparisons
 
 There are two ways to enable this comparison using the Scala 3 `CanEqual` type class.
 For simple cases like this, your class can *derive* the `CanEqual` class:
 
+{% tabs multiversal-equality-derives-CanEqual %}
+
+{% tab 'Scala 3 Only' %}
+
 ```scala
 // Option 1
 case class Dog(name: String) derives CanEqual
 ```
 
+{% endtab %}
+
+{% endtabs %}
+
 As you’ll see in a few moments, when you need more flexibility you can also use this syntax:
 
+{% tabs multiversal-equality-given-CanEqual %}
+
+{% tab 'Scala 3 Only' %}
+
 ```scala
 // Option 2
 case class Dog(name: String)
 given CanEqual[Dog, Dog] = CanEqual.derived
 ```
 
+{% endtab %}
+
+{% endtabs %}
+
 Either of those two approaches now let `Dog` instances to be compared to each other.
 
 
@@ -82,11 +107,19 @@ Either of those two approaches now let `Dog` instances to be compared to each ot
 In a more real-world example, imagine you have an online bookstore and want to allow or disallow the comparison of physical, printed books, and audiobooks.
 With Scala 3 you start by enabling multiversal equality as shown in the previous example:
 
+{% tabs multiversal-equality-strictEquality-2 %}
+
+{% tab 'Scala 3 Only' %}
+
 ```scala
 // [1] add this import, or this command line flag: -language:strictEquality
 import scala.language.strictEquality
 ```
 
+{% endtab %}
+
+{% endtabs %}
+
 Then create your domain objects as usual:
 
 ```scala
@@ -113,6 +146,10 @@ case class AudioBook(
 
 Finally, use `CanEqual` to define which comparisons you want to allow:
 
+{% tabs multiversal-equality-CanEqual-allow-comps %}
+
+{% tab 'Scala 3 Only' %}
+
 ```scala
 // [3] create type class instances to define the allowed comparisons.
 //     allow `PrintedBook == PrintedBook`
@@ -131,6 +168,10 @@ val aBook = AudioBook("1984", "George Orwell", 2006, 682)
 println(pBook == aBook)   // compiler error
 ```
 
+{% endtab %}
+
+{% endtabs %}
+
 The last line of code results in this compiler error message:
 
 ````
@@ -145,12 +186,20 @@ This is how multiversal equality catches illegal type comparisons at compile tim
 That works as desired, but in some situations you may want to allow the comparison of physical books to audiobooks.
 When you want this, create these two additional equality comparisons:
 
+{% tabs multiversal-equality-additional-comps %}
+
+{% tab 'Scala 3 Only' %}
+
 ```scala
 // allow `PrintedBook == AudioBook`, and `AudioBook == PrintedBook`
 given CanEqual[PrintedBook, AudioBook] = CanEqual.derived
 given CanEqual[AudioBook, PrintedBook] = CanEqual.derived
 ```
 
+{% endtab %}
+
+{% endtabs %}
+
 Now you can compare physical books to audiobooks without a compiler error:
 
 ```scala