Merge pull request #2462 from byyue/dev-2452

Elaborate Regular Expression Patterns

Author: SethTisue

_tour/regular-expression-patterns.md

@@ -58,3 +58,35 @@ key: margin value: 0
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 ```
+
+Moreover, regular expressions can be used as patterns (in `match` expressions) to conveniently extract the matched groups:
+
+```scala mdoc
+def saveContactInfomation(contact: String): Unit = {
+  import scala.util.matching.Regex
+
+  val emailPattern: Regex = """^(\w+)@(\w+(.\w+)+)$""".r
+  val phonePattern: Regex = """^(\d{3}-\d{3}-\d{4})$""".r
+
+  contact match {
+    case emailPattern(localPart, domainName, _) => 
+      println(s"Hi $localPart, we have saved your email address.")
+    case phonePattern(phoneNumber) => 
+      println(s"Hi, we have saved your phone number $phoneNumber.")
+    case _ => 
+      println("Invalid contact information, neither an email address nor phone number.")
+  }
+}
+
+saveContactInfomation("123-456-7890")
+saveContactInfomation("[email protected]")
+saveContactInfomation("2 Franklin St, Mars, Milky Way")
+```
+
+The output would be:
+
+```
+Hi, we have saved your phone number 123-456-7890.
+Hi JohnSmith, we have saved your email address.
+Invalid contact information, neither an email address nor phone number.
+```