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Rewrite the pattern matching section
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@ -407,41 +407,55 @@ val otherGeorge = george.copy(phoneNumber = "9876")
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// 6. Pattern Matching
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/////////////////////////////////////////////////
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val me = Person("George", "1234")
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// Pattern matching is a powerful and commonly used feature in Scala. Here's how
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// you pattern match a case class. NB: Unlike other languages, Scala cases do
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// not have breaks.
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me match { case Person(name, number) => {
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"We matched someone : " + name + ", phone : " + number }}
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me match { case Person(name, number) => "Match : " + name; case _ => "Hm..." }
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me match { case Person("George", number) => "Match"; case _ => "Hm..." }
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me match { case Person("Kate", number) => "Match"; case _ => "Hm..." }
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me match { case Person("Kate", _) => "Girl"; case Person("George", _) => "Boy" }
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val kate = Person("Kate", "1234")
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kate match { case Person("Kate", _) => "Girl"; case Person("George", _) => "Boy" }
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// Regular expressions
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val email = "(.*)@(.*)".r // Invoking r on String makes it a Regex
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val serialKey = """(\d{5})-(\d{5})-(\d{5})-(\d{5})""".r // Using verbatim (multiline) syntax
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val matcher = (value: String) => {
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println(value match {
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case email(name, domain) => s"It was an email: $name"
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case serialKey(p1, p2, p3, p4) => s"Serial key: $p1, $p2, $p3, $p4"
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case _ => s"No match on '$value'" // default if no match found
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})
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def matchPerson(person: Person): String = person match {
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// Then you specify the patterns:
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case Person("George", number) => "We found George! His number is " + number
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case Person("Kate", number) => "We found Kate! Her number is " + number
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case Person(name, number) => "We matched someone : " + name + ", phone : " + number
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}
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matcher("mrbean@pyahoo.com") // => "It was an email: mrbean"
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matcher("nope..") // => "No match on 'nope..'"
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matcher("52917") // => "No match on '52917'"
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matcher("52752-16432-22178-47917") // => "Serial key: 52752, 16432, 22178, 47917"
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val email = "(.*)@(.*)".r // Define a regex for the next example.
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// Pattern matching might look familiar to the switch statements in the C family
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// of languages, but this is much more powerful. In Scala, you can match much
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// more:
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def matchEverything(obj: Any): String = obj match {
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// You can match values:
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case "Hello world" => "Got the string Hello world"
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// You can match by type:
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case x: Double => "Got a Double: " + x
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// You can specify conditions:
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case x: Int if x > 10000 => "Got a pretty big number!"
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// You can match case classes as before:
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case Person(name, number) => s"Got contact info for $name!"
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// You can match regular expressions:
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case email(name, domain) => s"Got email address $name@$domain"
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// You can match tuples:
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case (a: Int, b: Double, c: String) => s"Got a tuple: $a, $b, $c"
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// You can match data structures:
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case List(1, b, c) => s"Got a list with three elements and starts with 1: 1, $b, $c"
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// You can nest patterns:
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case List(List((1, 2,"YAY"))) => "Got a list of list of tuple"
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}
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// In fact, you can pattern match any object with an "unapply" method. This
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// feature is so powerful that Scala lets you define whole functions as
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// patterns:
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val patternFunc: Person => String = {
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case Person("George", number") => s"George's number: $number"
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case Person(name, number) => s"Random person's number: $number"
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}
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/////////////////////////////////////////////////
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