Scala 2 Exercises

file_reader_writer.scala

import java.io.{BufferedReader, BufferedWriter, FileReader, FileWriter}

def withFileWriter(filename: String) (handler: BufferedWriter => Unit): Unit = {
  val writer = new BufferedWriter(new FileWriter(filename))
  try handler(writer)
  finally writer.close()
}

def withFileReader(filename: String) (handler: BufferedReader => Unit): Unit = {
  val reader = new BufferedReader(new FileReader(filename))
  try handler(reader)
  finally reader.close()
}

withFileWriter("Hello.txt") {
  writer => { writer.write("Hello\n"); writer.write("World!") }
}

var result: String = ""

withFileReader("Hello.txt") {
  reader => { result = reader.readLine() + "\n" + reader.readLine() }
}

assert(result == "Hello\nWorld!")

flexible_fizz_buzz.scala

def flexibleFizzBuzz(start: Int, end: Int) (callback: String => Unit): Unit = {
    for (i <- Range(start, end)) {
      var output: String = ""
      if (i % 3 == 0) {
        output += "Fizz"
      }
      if (i % 5 == 0) {
        output += "Buzz"
      }
      if (output.isEmpty) {
        output = s"${i}"
      }
      callback(output)
    }
}

flexibleFizzBuzz(start = 1, end = 50) {
  i => println(i)
}

/*
Output:

1
2
Fizz
4
Buzz
Fizz
7
8
Fizz
Buzz
11
Fizz
13
14
FizzBuzz
16
17
Fizz
19
Buzz
Fizz
22
23
Fizz
Buzz
26
Fizz
28
29
FizzBuzz
31
32
Fizz
34
Buzz
Fizz
37
38
Fizz
Buzz
41
Fizz
43
44
FizzBuzz
46
47
Fizz
49

*/

recursive_messages.scala

class Msg(val id: Int, val parent: Option[Int], val text: String)
def printMessages(messages: Array[Msg]): Unit = {
  for (message <- messages) {
    var indent: Int = 0
    message.parent match {
      case Some(parent) => indent = parent + 2
      case None => indent = 0
    }
    println(" " * indent + s"#${message.id} ${message.text}")
  }
}

printMessages(Array[Msg](
  new Msg(0, None, "Hello"),
  new Msg(1, Some(0), "World"),
  new Msg(2, None, "I am Cow"),
  new Msg(3, Some(2), "Here me moo"),
  new Msg(4, Some(2), "Here I stand"),
  new Msg(5, Some(2), "I am Cow"),
  new Msg(6, Some(5), "Here me moo, moo"),
))

/*
Output: 

#0 Hello
  #1 World
#2 I am Cow
    #3 Here me moo
    #4 Here I stand
    #5 I am Cow
       #6 Here me moo, moo
 */