comparing word counting: std vs fs2

main.scala

//> using scala "3.3.1"
//> using lib "co.fs2::fs2-io:3.9.3"

import scala.util.*
import scala.io.Source

def safePrintln(s: Any): Either[Throwable, Unit] =
  try Right(println(s))
  catch case err: Throwable => Left(err)

def countWordsStd(fileName: String): Either[Throwable, Unit] =
  Using(Source.fromFile(fileName)) { source =>
    source.getLines
      .flatMap(_.split("\\s"))
      .map(_ => 1)
      .sum
  }.toEither.flatMap(safePrintln(_))

import fs2.*, Stream.*
import cats.effect.IO
import fs2.io.file.{Files, Path}

def stdout[A]: Pipe[IO, A, Unit] =
  _.evalMap(a => IO(println(a)))

// in the talk:
// io.linesR(fileName)
//   .flatMap(s => emits(s.split("\\s")))
//   .map(_ => 1)
//   .fold(0)(_ + _)
//   .to(stdout)
def countWordsFs2(fileName: String): IO[Unit] =
  Files[IO]
    .readUtf8Lines(Path(fileName))
    .flatMap(s => emits(s.split("\\s")))
    .map(_ => 1)
    .fold(0)(_ + _)
    .through(stdout)
    .compile
    .drain

import cats.effect.unsafe.implicits.global

@main def main =
  println("Using fs2:")
  countWordsFs2("lorem").unsafeRunSync()
  println("Using scala stdlib:")
  countWordsStd("lorem") match
    case Left(err) => println(err)
    case Right(_)  => println("Done")