Question

What is the meaning of <- clause in below code ?
Is it like an assignment ?

class Nested {

  var filesHere = (new java.io.File(".")).listFiles()

  def fileLines(file: java.io.File) =
    scala.io.Source.fromFile(file).getLines().toList

  def grep(pattern: String) =
    for (
      file <- filesHere 
      if (file.getName.endsWith(".scala"));
      line <- fileLines(file) 
      if line.trim().matches(pattern)
    ) println(file + ": " + line.trim)

}

Answer 1

It’s not quite like an assignment: more like a for-each loop, but better. You can read about it here.

scala> for(i <- List(1,2,3,4)) println(i)
1
2
3
4

So this basically says, for each individual item i in the collection List(1,2,3,4), call println(i).