Introduction to Scala Part2 : Collections

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List Traversable: Size Info Traversable: Element Retrieval Traversable: Addition Traversable: Conversion Traversable: Copying Operations Traversable: Map operations Traversable: Sub-collection retrieval operations Traversable: Folds Traversable: Subdivision operations

Traversable: Map operations

Operations:
- map,
- flatMap,
- collect
- collectFirst
Goal: produce a new collection by applying some function to collection elements.

collect and collectFirst methods will be see in course C#03

Map

def map[B](f: (A) ⇒ B): Traversable[B]

Map is a HOF that builds a new collection by applying a function to all elements of this collection.

Map

> List("John Snow", "Aria Stark", "Tyrion Lannister").flatMap(x => x.split(" "))
res0: List[String] = List(John, Snow, Aria, Stark, Tyrion, Lannister)

Split all the sentences in Lists of words

count the words in l

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package fp101.tp02.collections
object ExerciceMap {
  
  /**
   * Split all the sentences of a list l in lists of words
   * 
   * e.g: splitInWords(List("Hi", "Hello World", "Look who it is"))
   * should gives:
   * List(List(Hi), List(Hello, World), List(Look, who, it, is))
   * 
   * Hint: use Map
   */
  def splitInWords(l: List[String]) = ???
  
  /**
   * 
   * Using flatMap, count the number of Words from a list of sentences, 
   * e.g: countWords(List("Hi", "Hello World", "Look who it is"))
   * gives 7
   * 
   * 
   */
  def countWords(l: List[String]) = ???
}

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