Created
August 5, 2012 08:37
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Dateに対するOrderのインスタンス無くても動くらしい
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import scalaz._, Scalaz._ | |
import java.util.Date | |
case class Student(name: String, grade: Int, birthday: Date) | |
object Student { | |
implicit object StudentInstance extends Show[Student] with Order[Student] { | |
def show(s: Student) = s.toString.toList | |
def order(s1: Student, s2: Student) = | |
s1.grade ?|? s2.grade |+| s1.birthday ?|? s2.birthday | |
} | |
} | |
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) |
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