Agfdhyk

I am very new to Scala and I am not even sure how to describe my question properly, but I will do my best to explain with examples.
I want to filter a list of strings with a condition but that list contains a lot of commas. The list contains userID, artID and ratings. eg)

val lst = List("1,1,4", "1,1060,2", "3,123,5", "4,1210,5", "4,1213,4")

With 3,123,5 as an example, 3 is the userID, 123 is the artID and 5 is the rating.
What I want to do is take the ratings that is above 4 and return a list of (userID, artID) only (return as List[(String, String)]). I've been trying various ways but kept failing and I have no idea how to begin now.

You say you want to filter a "list of strings." So I take it your input might look like this.

val lst = List("1,1,4", "1,1060,2", "3,123,5", "4,1210,5", "4,1213,4")

That being the case there is the problem of making numeric comparisons of String elements.

"4"  < "5"  //true

"14" > "5"  //false

You can cast the String to an Int before comparison, but that should also include tests for casting failure.

Here's a slightly different approach that simply passes all rating strings, numeric or otherwise, that evaluates as greater than "4". Strings that don't split() into the correct number of sub-strings are filtered out.

lst.map(_.split(",")).collect{

  case Array(uID,aID,r) if r.length > 1 || r > "4" => (uID,aID)

}

//res0: List[(String,String)] = List((3, 123), (4, 1210))

Check this out:

scala> val lst = List("1,1,4", "1,1060,2", "3,123,5", "4,1210,5", "4,1213,4")

lst: List[String] = List(1,1,4, 1,1060,2, 3,123,5, 4,1210,5, 4,1213,4)



scala> lst.filter(x=> { val y=x.split(",").map(_.toInt); y(2)>4}).map(x=>{val y = x.split(","); (y(0),y(1))} )

res16: List[(String, String)] = List((3,123), (4,1210))



scala>

val lst = List("1,1,4", "1,1060,2", "3,123,5", "4,1210,5", "4,1213,4")



val res = lst

  .map(_.split(","))

  .collect {

    case Array(a,b,c) if c.toInt>4 => (a,b)

  }



println(res)

you can do that in various ways:

val lst = List("1,1,4", "1,1060,2", "3,123,5", "4,1210,5", "4,1213,4")



  val ans: List[(String, String)] = lst.filter(elem => elem.split(",")(2).toInt > 4).map { e =>

    val s = e.split(",")

    (s(0), s(1))

  }



  val ans2: List[(String, String)] = lst.map {

    _.split(",")

  } collect {

    case Array(a, b, c) if c.toInt > 4 => (a, b)

  }



  val ans3: List[(String, String)] = lst.foldLeft(List[(String, String)]()) {

    (a, b) => {

      val sp = b.split(",")

      if (sp(2).toInt > 4) {

        (sp(0), sp(1)) :: a

      } else a

    }

  }



  println(ans) //List((3,123), (4,1210))

  println(ans2) //List((3,123), (4,1210))

  println(ans3) //List((4,1210), (3,123))