From 07a0c4674e72ad76202929062949e7ba7f62eb03 Mon Sep 17 00:00:00 2001
From: gkepka <gkepka@virtuslab.com>
Date: Sun, 8 Sep 2024 13:00:11 +0200
Subject: [PATCH 1/2] Examples for binding patterns to variables

---
 _overviews/scala3-book/control-structures.md | 47 ++++++++++++++++++++
 _tour/pattern-matching.md                    | 37 +++++++++++++++
 2 files changed, 84 insertions(+)

diff --git a/_overviews/scala3-book/control-structures.md b/_overviews/scala3-book/control-structures.md
index 6598cb604..b982cf654 100644
--- a/_overviews/scala3-book/control-structures.md
+++ b/_overviews/scala3-book/control-structures.md
@@ -810,6 +810,53 @@ speak(Person("Bam Bam"))   // "Bam Bam says, Bam bam!"
 {% endtab %}
 {% endtabs %}
 
+#### Binding matched patterns to variables
+
+You can bind the matched pattern to a variable to use type-specific behavior.
+
+{% tabs pattern-binding class=tabs-scala-version %}
+{% tab 'Scala 2' for=pattern-binding %}
+```scala
+trait Animal {
+  val name: String
+}
+case class Cat(name: String) extends Animal {
+  def meow: String = "Meow"
+}
+case class Dog(name: String) extends Animal {
+  def bark: String = "Bark"
+}
+
+def speak(animal: Animal) = animal match {
+  case c @ Cat(name) if name == "Felix" => println(s"$name says, ${c.meow}!")
+  case d @ Dog(name) if name == "Rex" => println(s"$name says, ${d.bark}!")
+  case _ => println("I don't know you!")
+}
+
+speak(Cat("Felix")) // "Felix says, Meow!"
+speak(Dog("Rex"))   // "Rex says, Bark!"
+```
+{% endtab %}
+{% tab 'Scala 3' for=pattern-binding %}
+```scala
+trait Animal:
+  val name: String
+case class Cat(name: String) extends Animal:
+  def meow: String = "Meow"
+case class Dog(name: String) extends Animal:
+  def bark: String = "Bark"
+
+def speak(animal: Animal) = animal match
+  case c @ Cat(name) if name == "Felix" => println(s"$name says, ${c.meow}!")
+  case d @ Dog(name) if name == "Rex" => println(s"$name says, ${d.bark}!")
+  case _ => println("I don't know you!")
+
+speak(Cat("Felix")) // "Felix says, Meow!"
+speak(Dog("Rex"))   // "Rex says, Bark!"
+```
+{% endtab %}
+{% endtabs %}
+
 ### Using a `match` expression as the body of a method
 
 Because `match` expressions return a value, they can be used as the body of a method.
diff --git a/_tour/pattern-matching.md b/_tour/pattern-matching.md
index 1038e6be1..bca07f089 100644
--- a/_tour/pattern-matching.md
+++ b/_tour/pattern-matching.md
@@ -236,6 +236,43 @@ def goIdle(device: Device): String = device match
 
 `def goIdle` has a different behavior depending on the type of `Device`. This is useful when the case needs to call a method on the pattern. It is a convention to use the first letter of the type as the case identifier (`p` and `c` in this case).
 
+## Binding matched patterns to variables
+You can use variable binding to get type-dependent behavior while simultaneously extracting fields from the matched pattern.
+
+{% tabs pattern-matching-variable-binding class=tabs-scala-version %}
+{% tab 'Scala 2' for=pattern-matching-variable-binding %}
+```scala mdoc
+sealed trait Device
+case class Phone(model: String) extends Device {
+  def screenOff = "Turning screen off"
+}
+case class Computer(model: String) extends Device {
+  def screenSaverOn = "Turning screen saver on..."
+}
+
+def goIdle(device: Device): String = device match {
+  case p @ Phone(model) => s"$model: ${p.screenOff}" 
+  case c @ Computer(model) => s"$model: ${c.screenSaverOn}"
+}
+```
+{% endtab %}
+{% tab 'Scala 3' for=pattern-matching-variable-binding %}
+```scala
+sealed trait Device
+case class Phone(model: String) extends Device:
+  def screenOff = "Turning screen off"
+
+case class Computer(model: String) extends Device:
+  def screenSaverOn = "Turning screen saver on..."
+
+
+def goIdle(device: Device): String = device match
+  case p @ Phone(model) => s"$model: ${p.screenOff}"
+  case c @ Computer(model) => s"$model: ${c.screenSaverOn}"
+```
+{% endtab %}
+{% endtabs %}
+
 ## Sealed types
 
 You may have noticed that in the examples above the base types are qualified

From 8ec1d34527adb813140a26254b47510ffddcf3aa Mon Sep 17 00:00:00 2001
From: gkepka <gkepka@virtuslab.com>
Date: Sun, 15 Sep 2024 21:20:41 +0200
Subject: [PATCH 2/2] Fix double declaration of classes and functions

---
 _tour/pattern-matching.md | 20 ++------------------
 1 file changed, 2 insertions(+), 18 deletions(-)

diff --git a/_tour/pattern-matching.md b/_tour/pattern-matching.md
index bca07f089..a89c16775 100644
--- a/_tour/pattern-matching.md
+++ b/_tour/pattern-matching.md
@@ -242,15 +242,7 @@ You can use variable binding to get type-dependent behavior while simultaneously
 {% tabs pattern-matching-variable-binding class=tabs-scala-version %}
 {% tab 'Scala 2' for=pattern-matching-variable-binding %}
 ```scala mdoc
-sealed trait Device
-case class Phone(model: String) extends Device {
-  def screenOff = "Turning screen off"
-}
-case class Computer(model: String) extends Device {
-  def screenSaverOn = "Turning screen saver on..."
-}
-
-def goIdle(device: Device): String = device match {
+def goIdleWithModel(device: Device): String = device match {
   case p @ Phone(model) => s"$model: ${p.screenOff}" 
   case c @ Computer(model) => s"$model: ${c.screenSaverOn}"
 }
@@ -258,15 +250,7 @@ def goIdle(device: Device): String = device match {
 {% endtab %}
 {% tab 'Scala 3' for=pattern-matching-variable-binding %}
 ```scala
-sealed trait Device
-case class Phone(model: String) extends Device:
-  def screenOff = "Turning screen off"
-
-case class Computer(model: String) extends Device:
-  def screenSaverOn = "Turning screen saver on..."
-
-
-def goIdle(device: Device): String = device match
+def goIdleWithModel(device: Device): String = device match
   case p @ Phone(model) => s"$model: ${p.screenOff}"
   case c @ Computer(model) => s"$model: ${c.screenSaverOn}"
 ```