Quick dirty and recursive implementation of contains string function.

CompareApp.scala

object ContainsApp extends App {

  def contains(substr: String, string: String): Boolean ={

    var bool = false

    def impl(letters: List[Char], word: List[Char], firstPass: Boolean = true): List[Char] ={

      if(letters.isEmpty || word.isEmpty){
         List()

      } else if(firstPass && (letters.head != word.head)) {
        //we want to force until we find a match
        impl(letters, word.tail)

      } else {
        if(letters.head == word.head){

          if(letters.length == 1)
            word
          else
            impl(letters.tail, word.tail, firstPass = false)

        } else {
          List()
        }
      }
    }

    val arr1 = substr.toList
    val arr2 = string.toList

    if (substr.length == 0) {
      false
    } else {
      if(impl(arr1, arr2).isEmpty)
        false
      else
        true
    }
  }


  println(contains("ll", "Hello world").toString)

}