Scala: drop elements in Sequence

Question

Can I reduce the loop inside my method with map or is there a shorter implementation of this code that's dropping elements in sequence?

// Method that drops one element in sequence
def drop_Val_In_List[String](ls: Seq[String], value: String): Seq[String] = {
 val index = ls.indexOf(value) //index is -1 if there is no matc
 if (index < 0) {
 ls
 } else if (index == 0) {
 ls.tail
 } else {
 // splitAt keeps the matching element in the second group
 val (a, b) = ls.splitAt(index)
 a ++ b.tail
 }
}
val KeepCols = Seq("id", "type", "month", "car", "road")
// Generalization of the above method to drop multiple elements
def drop_Val_List_In_List[String](ls: Seq[String], in_ls: Seq[String]): Seq[String] = {
 var tmp_ = ls
 //println(tmp.getClass)
 for(x <- in_ls ){ // should work without var x
 tmp_ = drop_Val_In_List(tmp_, x)
 }
 tmp_;
}
val tmp = drop_Val_List_In_List(KeepCols, List("id", "type", "month"))
```

• pacmaninbw: Welcome to the Code Review site where we review working code and provide suggestions on how to improve that code. Code that is not working as expected is considered off-topic and the question may be closed by the community. This type of question is more appropriate on stack overflow, but please read their guidelines for asking a good question first.
• Sᴀᴍ Onᴇᴌᴀ: Welcome to Code Review. It appears that you updated the code in revision 2 and removed the text about an error in revision 3. However, trying the code in multiple online tools shows there is still an error on that line that calls drop_Val_In_List() i.e.: type mismatch; found : java.lang.String; required: String(in method drop_Val_List_In_List)
• James Flash: I appreciate your observation. Now it should work

Answer 1

Follow the naming convention of the language

For scala, this is here. Spell methods and variables in lower camel case:

drop_Val_In_List
drop_Val_List_In_List
in_ls

Use the most appropriate data structure

To me, it seems like you want a set, not a sequence/list. Set also has the method you want:

val KeepCols = Set("id", "type", "month", "car", "road")
val tmp = KeepCols.diff(Set("id", "type", "month"))

If you don't want to use a set, Seq also has diff.