Regular expression in compiler design examples

This property is called representation independence. Have seen in the examples in this section that they enable patterns that have nothing to do with the data type of the object thatвЂ™s selected on. Extractors break this link between data representations and patterns. Succeeds, you know that the selector expression is an instance of class C. This means that the name of the class in a constructor pattern corresponds to the concrete representation type of the selector object. 26.6 Extractors versus case classesД®ven though they are very useful, case classes have one shortcoming: they expose the concrete representation of data. These support analogous injections and extractions for arrays. Very similar deп¬Ѓnitions exist in the object scala.Array. It also contains an unapplySeq method that returns all elements of the list as a sequence. ThatвЂ™s what lets you write expressions such as: The List object contains an apply method that takes a variable number of arguments. An extractor that deп¬Ѓnes an unapplySeq method.Listing 26.6 shows the relevant deп¬Ѓnitions:Дef unapplySeq(x: List ): Option] = Some (x) For instance, patterns of the form List(.) are possible because the scala.List companion object is an extractor that deп¬Ѓnes an unapplySeq method. In fact, these sequence patterns are all implemented using extractors in the standard Scala library. You saw in Section 15.2 that you can access the elements of a list or an array using sequence patterns such as: Subdoms: Seq = WrappedArray(epfl, support) 26.5 Extractors and sequence patterns Scala> val s = val ExpandedEMail(name, topdom, subdoms _ *) = s name: String = tom String literals and regular expressionsД®lement is a sequence of names representing the domain.A longer example: Parallel discrete event simulation.Better performance through thread reuse.Conversions between Java and Scala collections.Implicit conversion to an expected type.Selecting mutable versus immutable collections.

Regular expression in compiler design examples