Iris data set reader example

iris_reader.scala

import util.control.Exception._
def using[R <: { def close() }, A](resource: R)(f: R => A): A = ultimately {
  ignoring(classOf[Throwable]) apply resource.close()
} apply f(resource)

case class Sepal(length: Double, width: Double)
case class Petal(length: Double, width: Double)
case class Species(name: String)

case class Iris(sepal: Sepal, petal: Petal, species: Species)

def extract(line: String): Option[Iris] = line.split(",") match {
  case Array(sl, sw, pl, pw, s) =>
    Some(Iris(Sepal(sl.toDouble, sw.toDouble), Petal(pl.toDouble, pw.toDouble), Species(s)))
  case _ => None
}

import java.io._

println("---(while)---")
using(new FileReader("iris.csv")) { fr =>
  using(new BufferedReader(fr)) { br =>
    var line: String = null
    while ({line = br.readLine(); line != null}) { println(line) }
  }
}

println("---(foreach)---")
using(new FileReader("iris.csv")) { fr =>
  using(new BufferedReader(fr)) { br =>
    Iterator.continually(br.readLine()).takeWhile(_ != null).foreach { line => println(line) }
  }
}

println("---(map)---")
try {
  using(new FileReader("iris.csv")) { fr =>
    using(new BufferedReader(fr)) { br =>
      Iterator.continually(br.readLine()).takeWhile(_ != null).map { line => extract(line) }
    }.toSeq.flatten
  }.foreach(iris => println(iris))
} catch { case e => e.printStackTrace()
  /* java.io.IOException: Stream closed
        at java.io.BufferedReader.ensureOpen(BufferedReader.java:97)
        at java.io.BufferedReader.readLine(BufferedReader.java:292)
        at java.io.BufferedReader.readLine(BufferedReader.java:362)
        at Main$$anon$1$$anonfun$2$$anonfun$apply$5$$anonfun$apply$6.apply(reader.scala:32) */
}

println("---(foldLeft)---")
using(new FileReader("iris.csv")) { fr =>
  using(new BufferedReader(fr)) { br =>
    Iterator.continually(br.readLine()).takeWhile(_ != null)
      .foldLeft(List[Option[Iris]]()) { case (seq, line) => extract(line) :: seq }
  }.flatten
}.foreach(iris => println(iris))