Scala Library: scala.math.Ordering.String Feb 15, 2016 scala.math.Ordering.String implicit object String extends StringOrdering Source Ordering.scala - Blame Ordering.scala - History Type Members class Ops extends AnyRef This inner class defines comparison operators available for T . Definition Classes Ordering Value Members From java.util.Comparator def reversed(): Comparator[String] Definition Classes Comparator (defined at java.util.Comparator) def thenComparing(arg0: Comparator[_ >: String]): Comparator[String] Definition Classes Comparator (defined at java.util.Comparator) def thenComparingDouble(arg0: ToDoubleFunction[_ >: String]): Comparator[String] Definition Classes Comparator (defined at java.util.Comparator) def thenComparingInt(arg0: ToIntFunction[_ >: String]): Comparator[String] Definition Classes Comparator (defined at java.util.Comparator) def thenComparingLong(arg0: ToLongFunction[_ >: String]): Comparator[String] Definition Classes Comparator (defined at java.util.Comparator) def thenComparing[U <: Comparable[_ >: U]](arg0: java.util.function.Function[_ >: String, _ <: U]): Comparator[String] Definition Classes Comparator (defined at java.util.Comparator) def thenComparing[U](arg0: java.util.function.Function[_ >: String, _ <: U], arg1: Comparator[_ >: U]): Comparator[String] Definition Classes Comparator (defined at java.util.Comparator) Value Members From scala.math.Ordering def equiv(x: String, y: String): Boolean Return true if x == y in the ordering. Definition Classes Ordering → PartialOrdering → Equiv (defined at scala.math.Ordering) def gt(x: String, y: String): Boolean Return true if x > y in the ordering. Definition Classes Ordering → PartialOrdering (defined at scala.math.Ordering) def gteq(x: String, y: String): Boolean Return true if x >= y in the ordering. Definition Classes Ordering → PartialOrdering (defined at scala.math.Ordering) def lt(x: String, y: String): Boolean Return true if x < y in the ordering. Definition Classes Ordering → PartialOrdering (defined at scala.math.Ordering) def lteq(x: String, y: String): Boolean Return true if x <= y in the ordering. Definition Classes Ordering → PartialOrdering (defined at scala.math.Ordering) def max(x: String, y: String): String Return x if x >= y , otherwise y . Definition Classes Ordering (defined at scala.math.Ordering) def min(x: String, y: String): String Return x if x <= y , otherwise y . Definition Classes Ordering (defined at scala.math.Ordering) implicit def mkOrderingOps(lhs: String): Ops This implicit method augments T with the comparison operators defined in scala.math.Ordering.Ops . Definition Classes Ordering (defined at scala.math.Ordering) def on[U](f: (U) ⇒ String): Ordering[U] Given f, a function from U into T, creates an Ordering[U] whose compare function is equivalent to: def compare(x:U, y:U) = Ordering[T].compare(f(x), f(y)) Definition Classes Ordering (defined at scala.math.Ordering) def reverse: Ordering[String] Return the opposite ordering of this one. Definition Classes Ordering → PartialOrdering (defined at scala.math.Ordering) def tryCompare(x: String, y: String): Some[Int] Returns whether a comparison between x and y is defined, and if so the result of compare(x, y) . Definition Classes Ordering → PartialOrdering (defined at scala.math.Ordering) Value Members From scala.math.Ordering.StringOrdering def compare(x: String, y: String): Int Returns an integer whose sign communicates how x compares to y. The result sign has the following meaning: negative if x < y positive if x > y zero otherwise (if x == y) Definition Classes StringOrdering → Ordering → Comparator (defined at scala.math.Ordering.StringOrdering) Full Source: /* __ *\ ** ________ ___ / / ___ Scala API ** ** / __/ __// _ | / / / _ | (c) 2003-2013, LAMP/EPFL ** ** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ ** ** /____/\___/_/ |_/____/_/ | | ** ** |/ ** \* */ package scala package math import java.util.Comparator import scala.language.{implicitConversions, higherKinds} /** Ordering is a trait whose instances each represent a strategy for sorting * instances of a type. * * Ordering's companion object defines many implicit objects to deal with * subtypes of AnyVal (e.g. Int, Double), String, and others. * * To sort instances by one or more member variables, you can take advantage * of these built-in orderings using Ordering.by and Ordering.on: * * {{{ * import scala.util.Sorting * val pairs = Array(("a", 5, 2), ("c", 3, 1), ("b", 1, 3)) * * // sort by 2nd element * Sorting.quickSort(pairs)(Ordering.by[(String, Int, Int), Int](_._2)) * * // sort by the 3rd element, then 1st * Sorting.quickSort(pairs)(Ordering[(Int, String)].on(x => (x._3, x._1))) * }}} * * An Ordering[T] is implemented by specifying compare(a:T, b:T), which * decides how to order two instances a and b. Instances of Ordering[T] can be * used by things like scala.util.Sorting to sort collections like Array[T]. * * For example: * * {{{ * import scala.util.Sorting * * case class Person(name:String, age:Int) * val people = Array(Person("bob", 30), Person("ann", 32), Person("carl", 19)) * * // sort by age * object AgeOrdering extends Ordering[Person] { * def compare(a:Person, b:Person) = a.age compare b.age * } * Sorting.quickSort(people)(AgeOrdering) * }}} * * This trait and scala.math.Ordered both provide this same functionality, but * in different ways. A type T can be given a single way to order itself by * extending Ordered. Using Ordering, this same type may be sorted in many * other ways. Ordered and Ordering both provide implicits allowing them to be * used interchangeably. * * You can import scala.math.Ordering.Implicits to gain access to other * implicit orderings. * * @author Geoffrey Washburn * @version 0.9.5, 2008-04-15 * @since 2.7 * @see [[scala.math.Ordered]], [[scala.util.Sorting]] */ @annotation.implicitNotFound(msg = "No implicit Ordering defined for ${T}.") trait Ordering[T] extends Comparator[T] with PartialOrdering[T] with Serializable { outer => /** Returns whether a comparison between `x` and `y` is defined, and if so * the result of `compare(x, y)`. */ def tryCompare(x: T, y: T) = Some(compare(x, y)) /** Returns an integer whose sign communicates how x compares to y. * * The result sign has the following meaning: * * - negative if x < y * - positive if x > y * - zero otherwise (if x == y) */ def compare(x: T, y: T): Int /** Return true if `x` <= `y` in the ordering. */ override def lteq(x: T, y: T): Boolean = compare(x, y) <= 0 /** Return true if `x` >= `y` in the ordering. */ override def gteq(x: T, y: T): Boolean = compare(x, y) >= 0 /** Return true if `x` < `y` in the ordering. */ override def lt(x: T, y: T): Boolean = compare(x, y) < 0 /** Return true if `x` > `y` in the ordering. */ override def gt(x: T, y: T): Boolean = compare(x, y) > 0 /** Return true if `x` == `y` in the ordering. */ override def equiv(x: T, y: T): Boolean = compare(x, y) == 0 /** Return `x` if `x` >= `y`, otherwise `y`. */ def max(x: T, y: T): T = if (gteq(x, y)) x else y /** Return `x` if `x` <= `y`, otherwise `y`. */ def min(x: T, y: T): T = if (lteq(x, y)) x else y /** Return the opposite ordering of this one. */ override def reverse: Ordering[T] = new Ordering[T] { override def reverse = outer def compare(x: T, y: T) = outer.compare(y, x) } /** Given f, a function from U into T, creates an Ordering[U] whose compare * function is equivalent to: * * {{{ * def compare(x:U, y:U) = Ordering[T].compare(f(x), f(y)) * }}} */ def on[U](f: U => T): Ordering[U] = new Ordering[U] { def compare(x: U, y: U) = outer.compare(f(x), f(y)) } /** This inner class defines comparison operators available for `T`. */ class Ops(lhs: T) { def <(rhs: T) = lt(lhs, rhs) def <=(rhs: T) = lteq(lhs, rhs) def >(rhs: T) = gt(lhs, rhs) def >=(rhs: T) = gteq(lhs, rhs) def equiv(rhs: T) = Ordering.this.equiv(lhs, rhs) def max(rhs: T): T = Ordering.this.max(lhs, rhs) def min(rhs: T): T = Ordering.this.min(lhs, rhs) } /** This implicit method augments `T` with the comparison operators defined * in `scala.math.Ordering.Ops`. */ implicit def mkOrderingOps(lhs: T): Ops = new Ops(lhs) } trait LowPriorityOrderingImplicits { /** This would conflict with all the nice implicit Orderings * available, but thanks to the magic of prioritized implicits * via subclassing we can make `Ordered[A] => Ordering[A]` only * turn up if nothing else works. Since `Ordered[A]` extends * `Comparable[A]` anyway, we can throw in some Java interop too. */ implicit def ordered[A <% Comparable[A]]: Ordering[A] = new Ordering[A] { def compare(x: A, y: A): Int = x compareTo y } implicit def comparatorToOrdering[A](implicit cmp: Comparator[A]): Ordering[A] = new Ordering[A] { def compare(x: A, y: A) = cmp.compare(x, y) } } /** This is the companion object for the [[scala.math.Ordering]] trait. * * It contains many implicit orderings as well as well as methods to construct * new orderings. */ object Ordering extends LowPriorityOrderingImplicits { def apply[T](implicit ord: Ordering[T]) = ord trait ExtraImplicits { /** Not in the standard scope due to the potential for divergence: * For instance `implicitly[Ordering[Any]]` diverges in its presence. */ implicit def seqDerivedOrdering[CC[X] <: scala.collection.Seq[X], T](implicit ord: Ordering[T]): Ordering[CC[T]] = new Ordering[CC[T]] { def compare(x: CC[T], y: CC[T]): Int = { val xe = x.iterator val ye = y.iterator while (xe.hasNext && ye.hasNext) { val res = ord.compare(xe.next(), ye.next()) if (res != 0) return res } Ordering.Boolean.compare(xe.hasNext, ye.hasNext) } } /** This implicit creates a conversion from any value for which an * implicit `Ordering` exists to the class which creates infix operations. * With it imported, you can write methods as follows: * * {{{ * def lessThan[T: Ordering](x: T, y: T) = x < y * }}} */ implicit def infixOrderingOps[T](x: T)(implicit ord: Ordering[T]): Ordering[T]#Ops = new ord.Ops(x) } /** An object containing implicits which are not in the default scope. */ object Implicits extends ExtraImplicits { } /** Construct an Ordering[T] given a function `lt`. */ def fromLessThan[T](cmp: (T, T) => Boolean): Ordering[T] = new Ordering[T] { def compare(x: T, y: T) = if (cmp(x, y)) -1 else if (cmp(y, x)) 1 else 0 // overrides to avoid multiple comparisons override def lt(x: T, y: T): Boolean = cmp(x, y) override def gt(x: T, y: T): Boolean = cmp(y, x) override def gteq(x: T, y: T): Boolean = !cmp(x, y) override def lteq(x: T, y: T): Boolean = !cmp(y, x) } /** Given f, a function from T into S, creates an Ordering[T] whose compare * function is equivalent to: * * {{{ * def compare(x:T, y:T) = Ordering[S].compare(f(x), f(y)) * }}} * * This function is an analogue to Ordering.on where the Ordering[S] * parameter is passed implicitly. */ def by[T, S](f: T => S)(implicit ord: Ordering[S]): Ordering[T] = fromLessThan((x, y) => ord.lt(f(x), f(y))) trait UnitOrdering extends Ordering[Unit] { def compare(x: Unit, y: Unit) = 0 } implicit object Unit extends UnitOrdering trait BooleanOrdering extends Ordering[Boolean] { def compare(x: Boolean, y: Boolean) = (x, y) match { case (false, true) => -1 case (true, false) => 1 case _ => 0 } } implicit object Boolean extends BooleanOrdering trait ByteOrdering extends Ordering[Byte] { def compare(x: Byte, y: Byte) = x.toInt - y.toInt } implicit object Byte extends ByteOrdering trait CharOrdering extends Ordering[Char] { def compare(x: Char, y: Char) = x.toInt - y.toInt } implicit object Char extends CharOrdering trait ShortOrdering extends Ordering[Short] { def compare(x: Short, y: Short) = x.toInt - y.toInt } implicit object Short extends ShortOrdering trait IntOrdering extends Ordering[Int] { def compare(x: Int, y: Int) = if (x < y) -1 else if (x == y) 0 else 1 } implicit object Int extends IntOrdering trait LongOrdering extends Ordering[Long] { def compare(x: Long, y: Long) = if (x < y) -1 else if (x == y) 0 else 1 } implicit object Long extends LongOrdering trait FloatOrdering extends Ordering[Float] { outer => def compare(x: Float, y: Float) = java.lang.Float.compare(x, y) override def lteq(x: Float, y: Float): Boolean = x <= y override def gteq(x: Float, y: Float): Boolean = x >= y override def lt(x: Float, y: Float): Boolean = x < y override def gt(x: Float, y: Float): Boolean = x > y override def equiv(x: Float, y: Float): Boolean = x == y override def max(x: Float, y: Float): Float = math.max(x, y) override def min(x: Float, y: Float): Float = math.min(x, y) override def reverse: Ordering[Float] = new FloatOrdering { override def reverse = outer override def compare(x: Float, y: Float) = outer.compare(y, x) override def lteq(x: Float, y: Float): Boolean = outer.lteq(y, x) override def gteq(x: Float, y: Float): Boolean = outer.gteq(y, x) override def lt(x: Float, y: Float): Boolean = outer.lt(y, x) override def gt(x: Float, y: Float): Boolean = outer.gt(y, x) override def min(x: Float, y: Float): Float = outer.max(x, y) override def max(x: Float, y: Float): Float = outer.min(x, y) } } implicit object Float extends FloatOrdering trait DoubleOrdering extends Ordering[Double] { outer => def compare(x: Double, y: Double) = java.lang.Double.compare(x, y) override def lteq(x: Double, y: Double): Boolean = x <= y override def gteq(x: Double, y: Double): Boolean = x >= y override def lt(x: Double, y: Double): Boolean = x < y override def gt(x: Double, y: Double): Boolean = x > y override def equiv(x: Double, y: Double): Boolean = x == y override def max(x: Double, y: Double): Double = math.max(x, y) override def min(x: Double, y: Double): Double = math.min(x, y) override def reverse: Ordering[Double] = new DoubleOrdering { override def reverse = outer override def compare(x: Double, y: Double) = outer.compare(y, x) override def lteq(x: Double, y: Double): Boolean = outer.lteq(y, x) override def gteq(x: Double, y: Double): Boolean = outer.gteq(y, x) override def lt(x: Double, y: Double): Boolean = outer.lt(y, x) override def gt(x: Double, y: Double): Boolean = outer.gt(y, x) override def min(x: Double, y: Double): Double = outer.max(x, y) override def max(x: Double, y: Double): Double = outer.min(x, y) } } implicit object Double extends DoubleOrdering trait BigIntOrdering extends Ordering[BigInt] { def compare(x: BigInt, y: BigInt) = x.compare(y) } implicit object BigInt extends BigIntOrdering trait BigDecimalOrdering extends Ordering[BigDecimal] { def compare(x: BigDecimal, y: BigDecimal) = x.compare(y) } implicit object BigDecimal extends BigDecimalOrdering trait StringOrdering extends Ordering[String] { def compare(x: String, y: String) = x.compareTo(y) } implicit object String extends StringOrdering trait OptionOrdering[T] extends Ordering[Option[T]] { def optionOrdering: Ordering[T] def compare(x: Option[T], y: Option[T]) = (x, y) match { case (None, None) => 0 case (None, _) => -1 case (_, None) => 1 case (Some(x), Some(y)) => optionOrdering.compare(x, y) } } implicit def Option[T](implicit ord: Ordering[T]): Ordering[Option[T]] = new OptionOrdering[T] { val optionOrdering = ord } implicit def Iterable[T](implicit ord: Ordering[T]): Ordering[Iterable[T]] = new Ordering[Iterable[T]] { def compare(x: Iterable[T], y: Iterable[T]): Int = { val xe = x.iterator val ye = y.iterator while (xe.hasNext && ye.hasNext) { val res = ord.compare(xe.next(), ye.next()) if (res != 0) return res } Boolean.compare(xe.hasNext, ye.hasNext) } } implicit def Tuple2[T1, T2](implicit ord1: Ordering[T1], ord2: Ordering[T2]): Ordering[(T1, T2)] = new Ordering[(T1, T2)]{ def compare(x: (T1, T2), y: (T1, T2)): Int = { val compare1 = ord1.compare(x._1, y._1) if (compare1 != 0) return compare1 val compare2 = ord2.compare(x._2, y._2) if (compare2 != 0) return compare2 0 } } implicit def Tuple3[T1, T2, T3](implicit ord1: Ordering[T1], ord2: Ordering[T2], ord3: Ordering[T3]) : Ordering[(T1, T2, T3)] = new Ordering[(T1, T2, T3)]{ def compare(x: (T1, T2, T3), y: (T1, T2, T3)): Int = { val compare1 = ord1.compare(x._1, y._1) if (compare1 != 0) return compare1 val compare2 = ord2.compare(x._2, y._2) if (compare2 != 0) return compare2 val compare3 = ord3.compare(x._3, y._3) if (compare3 != 0) return compare3 0 } } implicit def Tuple4[T1, T2, T3, T4](implicit ord1: Ordering[T1], ord2: Ordering[T2], ord3: Ordering[T3], ord4: Ordering[T4]) : Ordering[(T1, T2, T3, T4)] = new Ordering[(T1, T2, T3, T4)]{ def compare(x: (T1, T2, T3, T4), y: (T1, T2, T3, T4)): Int = { val compare1 = ord1.compare(x._1, y._1) if (compare1 != 0) return compare1 val compare2 = ord2.compare(x._2, y._2) if (compare2 != 0) return compare2 val compare3 = ord3.compare(x._3, y._3) if (compare3 != 0) return compare3 val compare4 = ord4.compare(x._4, y._4) if (compare4 != 0) return compare4 0 } } implicit def Tuple5[T1, T2, T3, T4, T5](implicit ord1: Ordering[T1], ord2: Ordering[T2], ord3: Ordering[T3], ord4: Ordering[T4], ord5: Ordering[T5]): Ordering[(T1, T2, T3, T4, T5)] = new Ordering[(T1, T2, T3, T4, T5)]{ def compare(x: (T1, T2, T3, T4, T5), y: Tuple5[T1, T2, T3, T4, T5]): Int = { val compare1 = ord1.compare(x._1, y._1) if (compare1 != 0) return compare1 val compare2 = ord2.compare(x._2, y._2) if (compare2 != 0) return compare2 val compare3 = ord3.compare(x._3, y._3) if (compare3 != 0) return compare3 val compare4 = ord4.compare(x._4, y._4) if (compare4 != 0) return compare4 val compare5 = ord5.compare(x._5, y._5) if (compare5 != 0) return compare5 0 } } implicit def Tuple6[T1, T2, T3, T4, T5, T6](implicit ord1: Ordering[T1], ord2: Ordering[T2], ord3: Ordering[T3], ord4: Ordering[T4], ord5: Ordering[T5], ord6: Ordering[T6]): Ordering[(T1, T2, T3, T4, T5, T6)] = new Ordering[(T1, T2, T3, T4, T5, T6)]{ def compare(x: (T1, T2, T3, T4, T5, T6), y: (T1, T2, T3, T4, T5, T6)): Int = { val compare1 = ord1.compare(x._1, y._1) if (compare1 != 0) return compare1 val compare2 = ord2.compare(x._2, y._2) if (compare2 != 0) return compare2 val compare3 = ord3.compare(x._3, y._3) if (compare3 != 0) return compare3 val compare4 = ord4.compare(x._4, y._4) if (compare4 != 0) return compare4 val compare5 = ord5.compare(x._5, y._5) if (compare5 != 0) return compare5 val compare6 = ord6.compare(x._6, y._6) if (compare6 != 0) return compare6 0 } } implicit def Tuple7[T1, T2, T3, T4, T5, T6, T7](implicit ord1: Ordering[T1], ord2: Ordering[T2], ord3: Ordering[T3], ord4: Ordering[T4], ord5: Ordering[T5], ord6: Ordering[T6], ord7: Ordering[T7]): Ordering[(T1, T2, T3, T4, T5, T6, T7)] = new Ordering[(T1, T2, T3, T4, T5, T6, T7)]{ def compare(x: (T1, T2, T3, T4, T5, T6, T7), y: (T1, T2, T3, T4, T5, T6, T7)): Int = { val compare1 = ord1.compare(x._1, y._1) if (compare1 != 0) return compare1 val compare2 = ord2.compare(x._2, y._2) if (compare2 != 0) return compare2 val compare3 = ord3.compare(x._3, y._3) if (compare3 != 0) return compare3 val compare4 = ord4.compare(x._4, y._4) if (compare4 != 0) return compare4 val compare5 = ord5.compare(x._5, y._5) if (compare5 != 0) return compare5 val compare6 = ord6.compare(x._6, y._6) if (compare6 != 0) return compare6 val compare7 = ord7.compare(x._7, y._7) if (compare7 != 0) return compare7 0 } } implicit def Tuple8[T1, T2, T3, T4, T5, T6, T7, T8](implicit ord1: Ordering[T1], ord2: Ordering[T2], ord3: Ordering[T3], ord4: Ordering[T4], ord5: Ordering[T5], ord6: Ordering[T6], ord7: Ordering[T7], ord8: Ordering[T8]): Ordering[(T1, T2, T3, T4, T5, T6, T7, T8)] = new Ordering[(T1, T2, T3, T4, T5, T6, T7, T8)]{ def compare(x: (T1, T2, T3, T4, T5, T6, T7, T8), y: (T1, T2, T3, T4, T5, T6, T7, T8)): Int = { val compare1 = ord1.compare(x._1, y._1) if (compare1 != 0) return compare1 val compare2 = ord2.compare(x._2, y._2) if (compare2 != 0) return compare2 val compare3 = ord3.compare(x._3, y._3) if (compare3 != 0) return compare3 val compare4 = ord4.compare(x._4, y._4) if (compare4 != 0) return compare4 val compare5 = ord5.compare(x._5, y._5) if (compare5 != 0) return compare5 val compare6 = ord6.compare(x._6, y._6) if (compare6 != 0) return compare6 val compare7 = ord7.compare(x._7, y._7) if (compare7 != 0) return compare7 val compare8 = ord8.compare(x._8, y._8) if (compare8 != 0) return compare8 0 } } implicit def Tuple9[T1, T2, T3, T4, T5, T6, T7, T8, T9](implicit ord1: Ordering[T1], ord2: Ordering[T2], ord3: Ordering[T3], ord4: Ordering[T4], ord5: Ordering[T5], ord6: Ordering[T6], ord7: Ordering[T7], ord8 : Ordering[T8], ord9: Ordering[T9]): Ordering[(T1, T2, T3, T4, T5, T6, T7, T8, T9)] = new Ordering[(T1, T2, T3, T4, T5, T6, T7, T8, T9)]{ def compare(x: (T1, T2, T3, T4, T5, T6, T7, T8, T9), y: (T1, T2, T3, T4, T5, T6, T7, T8, T9)): Int = { val compare1 = ord1.compare(x._1, y._1) if (compare1 != 0) return compare1 val compare2 = ord2.compare(x._2, y._2) if (compare2 != 0) return compare2 val compare3 = ord3.compare(x._3, y._3) if (compare3 != 0) return compare3 val compare4 = ord4.compare(x._4, y._4) if (compare4 != 0) return compare4 val compare5 = ord5.compare(x._5, y._5) if (compare5 != 0) return compare5 val compare6 = ord6.compare(x._6, y._6) if (compare6 != 0) return compare6 val compare7 = ord7.compare(x._7, y._7) if (compare7 != 0) return compare7 val compare8 = ord8.compare(x._8, y._8) if (compare8 != 0) return compare8 val compare9 = ord9.compare(x._9, y._9) if (compare9 != 0) return compare9 0 } } } Interested in Scala?I send out weekly, personalized emails with articles and conference talks. 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