start_scalaz

example2.scala

import scalaz._, Scalaz._

case class User(id: String, pass: String)

object Main extends App {

  implicit object userShow extends Show[User] {
    def show(u: User) = u.toString.toList
  }

  implicit object userEq extends Equal[User] {
    def equal(u1: User, u2: User) = u1 == u2
  }

  def user(m: Map[String, String]): Option[User] = {
    (m.get("id") |@| m.get("pass")) { (id, pass) =>
      User(id, pass)
    }
  }

  user(Map("id" -> "takahashi", "pass" -> "hogehoge")) assert_=== Some(User("takahashi", "hogehoge"))
  user(Map.empty[String, String]) assert_=== None
}

order.scala

import scalaz._, Scalaz._
import java.util.Date

object JavaUtilDateOrdering {

  implicit object javaUtilDateOrdering extends Order[Date] {
    def order(d1: Date, d2: Date) = {
      if (d1.getTime == d2.getTime) {
        Ordering.EQ
      } else if (d1.getTime < d2.getTime) {
        Ordering.LT
      } else {
        Ordering.GT
      }
    }
  }

}

case class Student(name: String, grade: Int, birthday: Date)
object Student {
  implicit object StudentOrdering extends Order[Student] {
    def order(s1: Student, s2: Student) =
      s1.grade ?|? s2.grade |+| s1.birthday ?|? s2.birthday
  }

  implicit object StudentShow extends Show[Student] {
    def show(s: Student) = s.toString.toList
  }
}


object Main extends App {


  val format = new java.text.SimpleDateFormat("yyyy MM dd")
  val akari = Student("akari", 1, format.parse("1995 07 24"))
  val kyoko = Student("kyoko", 2, format.parse("1995 03 28"))
  val yui = Student("yui", 2, format.parse("1994 04 22"))
  val chinatsu = Student("chinatsu", 1, format.parse("1995 11 06"))

  List(akari, kyoko, yui, chinatsu).sorted(Order[Student].toScalaOrdering) assert_=== List(akari, chinatsu, yui, kyoko)

  println(List(akari, kyoko, yui, chinatsu).sorted(Order[Student].toScalaOrdering).mkString("\n"))

}