Count lines of scala code (omitting empty lines) in a directory, traversing any subdirectories

Question

I need to simply count lines of Scala code in a project, which includes some package(i.e. directory) hierarchy.

I'm not sure about the performance of the code below. Can you help improve it, if possible?

Also, in Java, we have reduce() in the Stream API, and I didn't find its counterpart in the Scala library, so ended with foldLeft().

import java.io.File
import scala.io.Source

object CountLoc {
  def main(args: Array[String]): Unit = {
    val parentDir: File = new File(System.getProperty("user.dir"))

    def traverse(dir: File): Int = {
      val all = dir.list().map(f => new File(dir.getAbsolutePath + "/" + f))
      val srcs = all.filter(!_.isDirectory).filter(_.getName.endsWith(".scala"))
      val dirs = all.filter(_.isDirectory)
      srcs.foldLeft(0)((i, f) => i + Source.fromFile(f).getLines().filterNot(_.isEmpty).toList.size) +
        dirs.toList.foldLeft(0)((i,d) => i + traverse(d))
    }

    println("LOC: " + traverse(parentDir))
  }
}

Why are you defining a function inside of a function? That's not a good idea for performance. — FreezePhoenix
– FreezePhoenix, Commented Aug 14, 2018 at 19:26

jwvh · Accepted Answer · 2018-08-14 21:06:51Z

1

Instead of collecting all the source files in one sweep, and all the sub-directories in another sweep, you could move the foldLeft() to the top level and deal with each element as it is encountered.

def traverse(dir :File) :Int =
  dir.listFiles().foldLeft(0){ case (sum,file) =>
    if (file.isDirectory)
      sum + traverse(file)
    else if (file.getName.endsWith(".scala"))
      sum + io.Source.fromFile(file).getLines().count(_.nonEmpty)
    else
      sum
  }

answered Aug 14, 2018 at 21:06

jwvh

1,4738 silver badges10 bronze badges

\$\begingroup\$ A cool one! Great minimalistic approach. ( to get it running, I've added import java.io.File and changed io.Source.fromFile to scala.io.Source.fromFile ) \$\endgroup\$

hartmut27
– hartmut27

2021-10-23 14:29:33 +00:00
Commented Oct 23, 2021 at 14:29
\$\begingroup\$ and replaced _.nonEmpty with _.trim.nonEmpty \$\endgroup\$

hartmut27
– hartmut27

2021-10-23 14:38:34 +00:00
Commented Oct 23, 2021 at 14:38

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