Generate all possible combinations of letters in scala lazily

lazyletters.scala

 implicit class RichLazyStringList(list: LazyList[String]) {
    def productWith(other: LazyList[String]): LazyList[String] =
      for {
        a <- list
        b <- other
      } yield a + b
  }
 
  LazyList
    .from(1)
    .map(charCount => LazyList.fill(charCount)(LazyList.from('a' to 'z').map(_.toString)))
    .flatMap(_.reduceLeft(_.productWith(_)))