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Scala example source code file (Predef.scala)

This example Scala source code file (Predef.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

a, annotation, any, array, arrayops, b, boolean, collection, int, io, string, use, wrappedarray

The Predef.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2002-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala

import scala.collection.{ mutable, immutable, generic }
import immutable.StringOps
import mutable.ArrayOps
import generic.CanBuildFrom
import scala.annotation.{ elidable, implicitNotFound }
import scala.annotation.elidable.ASSERTION
import scala.language.{implicitConversions, existentials}
import scala.io.StdIn

/** The `Predef` object provides definitions that are accessible in all Scala
 *  compilation units without explicit qualification.
 *
 *  === Commonly Used Types ===
 *  Predef provides type aliases for types which are commonly used, such as
 *  the immutable collection types [[scala.collection.immutable.Map]],
 *  [[scala.collection.immutable.Set]], and the [[scala.collection.immutable.List]]
 *  constructors ([[scala.collection.immutable.::]] and
 *  [[scala.collection.immutable.Nil]]).
 *
 *  === Console I/O ===
 *  Predef provides a number of simple functions for console I/O, such as
 *  `print`, `println`, `readLine`, `readInt`, etc. These functions are all
 *  aliases of the functions provided by [[scala.Console]].
 *
 *  === Assertions ===
 *
 *  A set of `assert` functions are provided for use as a way to document
 *  and dynamically check invariants in code. `assert` statements can be elided
 *  at runtime by providing the command line argument `-Xdisable-assertions` to
 *  the `scala` command.
 *
 *  Variants of `assert` intended for use with static analysis tools are also
 *  provided: `assume`, `require` and `ensuring`. `require` and `ensuring` are
 *  intended for use as a means of design-by-contract style specification
 *  of pre- and post-conditions on functions, with the intention that these
 *  specifications could be consumed by a static analysis tool. For instance,
 *
 *  {{{
 *  def addNaturals(nats: List[Int]): Int = {
 *    require(nats forall (_ >= 0), "List contains negative numbers")
 *    nats.foldLeft(0)(_ + _)
 *  } ensuring(_ >= 0)
 *  }}}
 *
 *  The declaration of `addNaturals` states that the list of integers passed should
 *  only contain natural numbers (i.e. non-negative), and that the result returned
 *  will also be natural. `require` is distinct from `assert` in that if the
 *  condition fails, then the caller of the function is to blame rather than a
 *  logical error having been made within `addNaturals` itself. `ensures` is a
 *  form of `assert` that declares the guarantee the function is providing with
 *  regards to it's return value.
 *
 *  === Implicit Conversions ===
 *  A number of commonly applied implicit conversions are also defined here, and
 *  in the parent type [[scala.LowPriorityImplicits]]. Implicit conversions
 *  are provided for the "widening" of numeric values, for instance, converting a
 *  Short value to a Long value as required, and to add additional higher-order
 *  functions to Array values. These are described in more detail in the documentation of [[scala.Array]].
 */
object Predef extends LowPriorityImplicits with DeprecatedPredef {
  /**
   * Retrieve the runtime representation of a class type. `classOf[T]` is equivalent to
   * the class literal `T.class` in Java.
   *
   * @example {{{
   * val listClass = classOf[List[_]]
   * // listClass is java.lang.Class[List[_]] = class scala.collection.immutable.List
   *
   * val mapIntString = classOf[Map[Int,String]]
   * // mapIntString is java.lang.Class[Map[Int,String]] = interface scala.collection.immutable.Map
   * }}}
   */
  def classOf[T]: Class[T] = null // This is a stub method. The actual implementation is filled in by the compiler.

  type String        = java.lang.String
  type Class[T]      = java.lang.Class[T]

  // miscelleaneous -----------------------------------------------------
  scala.`package`                         // to force scala package object to be seen.
  scala.collection.immutable.List         // to force Nil, :: to be seen.

  type Function[-A, +B] = Function1[A, B]

  type Map[A, +B] = immutable.Map[A, B]
  type Set[A]     = immutable.Set[A]
  val Map         = immutable.Map
  val Set         = immutable.Set

  // Manifest types, companions, and incantations for summoning
  @annotation.implicitNotFound(msg = "No ClassManifest available for ${T}.")
  @deprecated("Use `scala.reflect.ClassTag` instead", "2.10.0")
  type ClassManifest[T] = scala.reflect.ClassManifest[T]
  // TODO undeprecated until Scala reflection becomes non-experimental
  // @deprecated("This notion doesn't have a corresponding concept in 2.10, because scala.reflect.runtime.universe.TypeTag can capture arbitrary types. Use type tags instead of manifests, and there will be no need in opt manifests.", "2.10.0")
  type OptManifest[T]   = scala.reflect.OptManifest[T]
  @annotation.implicitNotFound(msg = "No Manifest available for ${T}.")
  // TODO undeprecated until Scala reflection becomes non-experimental
  // @deprecated("Use `scala.reflect.ClassTag` (to capture erasures) or scala.reflect.runtime.universe.TypeTag (to capture types) or both instead", "2.10.0")
  type Manifest[T]      = scala.reflect.Manifest[T]
  @deprecated("Use `scala.reflect.ClassTag` instead", "2.10.0")
  val ClassManifest     = scala.reflect.ClassManifest
  // TODO undeprecated until Scala reflection becomes non-experimental
  // @deprecated("Use `scala.reflect.ClassTag` (to capture erasures) or scala.reflect.runtime.universe.TypeTag (to capture types) or both instead", "2.10.0")
  val Manifest          = scala.reflect.Manifest
  // TODO undeprecated until Scala reflection becomes non-experimental
  // @deprecated("This notion doesn't have a corresponding concept in 2.10, because scala.reflect.runtime.universe.TypeTag can capture arbitrary types. Use type tags instead of manifests, and there will be no need in opt manifests.", "2.10.0")
  val NoManifest        = scala.reflect.NoManifest

  // TODO undeprecated until Scala reflection becomes non-experimental
  // @deprecated("Use scala.reflect.classTag[T] and scala.reflect.runtime.universe.typeTag[T] instead", "2.10.0")
  def manifest[T](implicit m: Manifest[T])           = m
  @deprecated("Use scala.reflect.classTag[T] instead", "2.10.0")
  def classManifest[T](implicit m: ClassManifest[T]) = m
  // TODO undeprecated until Scala reflection becomes non-experimental
  // @deprecated("This notion doesn't have a corresponding concept in 2.10, because scala.reflect.runtime.universe.TypeTag can capture arbitrary types. Use type tags instead of manifests, and there will be no need in opt manifests.", "2.10.0")
  def optManifest[T](implicit m: OptManifest[T])     = m

  // Minor variations on identity functions
  def identity[A](x: A): A         = x    // @see `conforms` for the implicit version
  @inline def implicitly[T](implicit e: T) = e    // for summoning implicit values from the nether world -- TODO: when dependent method types are on by default, give this result type `e.type`, so that inliner has better chance of knowing which method to inline in calls like `implicitly[MatchingStrategy[Option]].zero`
  @inline def locally[T](x: T): T  = x    // to communicate intent and avoid unmoored statements

  // errors and asserts -------------------------------------------------

  // !!! Remove this when possible - ideally for 2.11.
  // We are stuck with it a while longer because sbt's compiler interface
  // still calls it as of 0.12.2.
  @deprecated("Use `sys.error(message)` instead", "2.9.0")
  def error(message: String): Nothing = sys.error(message)

  /** Tests an expression, throwing an `AssertionError` if false.
   *  Calls to this method will not be generated if `-Xelide-below`
   *  is at least `ASSERTION`.
   *
   *  @see elidable
   *  @param assertion   the expression to test
   */
  @elidable(ASSERTION)
  def assert(assertion: Boolean) {
    if (!assertion)
      throw new java.lang.AssertionError("assertion failed")
  }

  /** Tests an expression, throwing an `AssertionError` if false.
   *  Calls to this method will not be generated if `-Xelide-below`
   *  is at least `ASSERTION`.
   *
   *  @see elidable
   *  @param assertion   the expression to test
   *  @param message     a String to include in the failure message
   */
  @elidable(ASSERTION) @inline
  final def assert(assertion: Boolean, message: => Any) {
    if (!assertion)
      throw new java.lang.AssertionError("assertion failed: "+ message)
  }

  /** Tests an expression, throwing an `AssertionError` if false.
   *  This method differs from assert only in the intent expressed:
   *  assert contains a predicate which needs to be proven, while
   *  assume contains an axiom for a static checker.  Calls to this method
   *  will not be generated if `-Xelide-below` is at least `ASSERTION`.
   *
   *  @see elidable
   *  @param assumption   the expression to test
   */
  @elidable(ASSERTION)
  def assume(assumption: Boolean) {
    if (!assumption)
      throw new java.lang.AssertionError("assumption failed")
  }

  /** Tests an expression, throwing an `AssertionError` if false.
   *  This method differs from assert only in the intent expressed:
   *  assert contains a predicate which needs to be proven, while
   *  assume contains an axiom for a static checker.  Calls to this method
   *  will not be generated if `-Xelide-below` is at least `ASSERTION`.
   *
   *  @see elidable
   *  @param assumption   the expression to test
   *  @param message      a String to include in the failure message
   */
  @elidable(ASSERTION) @inline
  final def assume(assumption: Boolean, message: => Any) {
    if (!assumption)
      throw new java.lang.AssertionError("assumption failed: "+ message)
  }

  /** Tests an expression, throwing an `IllegalArgumentException` if false.
   *  This method is similar to `assert`, but blames the caller of the method
   *  for violating the condition.
   *
   *  @param requirement   the expression to test
   */
  def require(requirement: Boolean) {
    if (!requirement)
      throw new IllegalArgumentException("requirement failed")
  }

  /** Tests an expression, throwing an `IllegalArgumentException` if false.
   *  This method is similar to `assert`, but blames the caller of the method
   *  for violating the condition.
   *
   *  @param requirement   the expression to test
   *  @param message       a String to include in the failure message
   */
  @inline final def require(requirement: Boolean, message: => Any) {
    if (!requirement)
      throw new IllegalArgumentException("requirement failed: "+ message)
  }

  /** `???` can be used for marking methods that remain to be implemented.
   *  @throws  A `NotImplementedError`
   */
  def ??? : Nothing = throw new NotImplementedError

  // tupling ------------------------------------------------------------

  @deprecated("Use built-in tuple syntax or Tuple2 instead", "2.11.0")
  type Pair[+A, +B] = Tuple2[A, B]
  @deprecated("Use built-in tuple syntax or Tuple2 instead", "2.11.0")
  object Pair {
    def apply[A, B](x: A, y: B) = Tuple2(x, y)
    def unapply[A, B](x: Tuple2[A, B]): Option[Tuple2[A, B]] = Some(x)
  }

  @deprecated("Use built-in tuple syntax or Tuple3 instead", "2.11.0")
  type Triple[+A, +B, +C] = Tuple3[A, B, C]
  @deprecated("Use built-in tuple syntax or Tuple3 instead", "2.11.0")
  object Triple {
    def apply[A, B, C](x: A, y: B, z: C) = Tuple3(x, y, z)
    def unapply[A, B, C](x: Tuple3[A, B, C]): Option[Tuple3[A, B, C]] = Some(x)
  }

  // implicit classes -----------------------------------------------------

  implicit final class ArrowAssoc[A](private val self: A) extends AnyVal {
    @inline def -> [B](y: B): Tuple2[A, B] = Tuple2(self, y)
    def →[B](y: B): Tuple2[A, B] = ->(y)
  }

  implicit final class Ensuring[A](private val self: A) extends AnyVal {
    def ensuring(cond: Boolean): A = { assert(cond); self }
    def ensuring(cond: Boolean, msg: => Any): A = { assert(cond, msg); self }
    def ensuring(cond: A => Boolean): A = { assert(cond(self)); self }
    def ensuring(cond: A => Boolean, msg: => Any): A = { assert(cond(self), msg); self }
  }

  implicit final class StringFormat[A](private val self: A) extends AnyVal {
    /** Returns string formatted according to given `format` string.
     *  Format strings are as for `String.format`
     *  (@see java.lang.String.format).
     */
    @inline def formatted(fmtstr: String): String = fmtstr format self
  }

  // TODO: remove, only needed for binary compatibility of 2.11.0-RC1 with 2.11.0-M8
  // note that `private[scala]` becomes `public` in bytecode
  private[scala] final class StringAdd[A](private val self: A) extends AnyVal {
    def +(other: String): String = String.valueOf(self) + other
  }
  private[scala] def StringAdd(x: Any): Any = new StringAdd(x)

  // SI-8229 retaining the pre 2.11 name for source compatibility in shadowing this implicit
  implicit final class any2stringadd[A](private val self: A) extends AnyVal {
    def +(other: String): String = String.valueOf(self) + other
  }

  implicit final class RichException(private val self: Throwable) extends AnyVal {
    import scala.compat.Platform.EOL
    @deprecated("Use Throwable#getStackTrace", "2.11.0") def getStackTraceString = self.getStackTrace().mkString("", EOL, EOL)
  }

  implicit final class SeqCharSequence(val __sequenceOfChars: scala.collection.IndexedSeq[Char]) extends CharSequence {
    def length: Int                                     = __sequenceOfChars.length
    def charAt(index: Int): Char                        = __sequenceOfChars(index)
    def subSequence(start: Int, end: Int): CharSequence = new SeqCharSequence(__sequenceOfChars.slice(start, end))
    override def toString                               = __sequenceOfChars mkString ""
  }

  implicit final class ArrayCharSequence(val __arrayOfChars: Array[Char]) extends CharSequence {
    def length: Int                                     = __arrayOfChars.length
    def charAt(index: Int): Char                        = __arrayOfChars(index)
    def subSequence(start: Int, end: Int): CharSequence = new runtime.ArrayCharSequence(__arrayOfChars, start, end)
    override def toString                               = __arrayOfChars mkString ""
  }

  implicit val StringCanBuildFrom: CanBuildFrom[String, Char, String] = new CanBuildFrom[String, Char, String] {
    def apply(from: String) = apply()
    def apply()             = mutable.StringBuilder.newBuilder
  }

  @inline implicit def augmentString(x: String): StringOps = new StringOps(x)
  @inline implicit def unaugmentString(x: StringOps): String = x.repr

  // printing and reading -----------------------------------------------

  def print(x: Any) = Console.print(x)
  def println() = Console.println()
  def println(x: Any) = Console.println(x)
  def printf(text: String, xs: Any*) = Console.print(text.format(xs: _*))

  // views --------------------------------------------------------------

  implicit def tuple2ToZippedOps[T1, T2](x: (T1, T2))                           = new runtime.Tuple2Zipped.Ops(x)
  implicit def tuple3ToZippedOps[T1, T2, T3](x: (T1, T2, T3))                   = new runtime.Tuple3Zipped.Ops(x)

  implicit def genericArrayOps[T](xs: Array[T]): ArrayOps[T] = (xs match {
    case x: Array[AnyRef]  => refArrayOps[AnyRef](x)
    case x: Array[Boolean] => booleanArrayOps(x)
    case x: Array[Byte]    => byteArrayOps(x)
    case x: Array[Char]    => charArrayOps(x)
    case x: Array[Double]  => doubleArrayOps(x)
    case x: Array[Float]   => floatArrayOps(x)
    case x: Array[Int]     => intArrayOps(x)
    case x: Array[Long]    => longArrayOps(x)
    case x: Array[Short]   => shortArrayOps(x)
    case x: Array[Unit]    => unitArrayOps(x)
    case null              => null
  }).asInstanceOf[ArrayOps[T]]

  implicit def booleanArrayOps(xs: Array[Boolean]): ArrayOps[Boolean] = new ArrayOps.ofBoolean(xs)
  implicit def byteArrayOps(xs: Array[Byte]): ArrayOps[Byte]          = new ArrayOps.ofByte(xs)
  implicit def charArrayOps(xs: Array[Char]): ArrayOps[Char]          = new ArrayOps.ofChar(xs)
  implicit def doubleArrayOps(xs: Array[Double]): ArrayOps[Double]    = new ArrayOps.ofDouble(xs)
  implicit def floatArrayOps(xs: Array[Float]): ArrayOps[Float]       = new ArrayOps.ofFloat(xs)
  implicit def intArrayOps(xs: Array[Int]): ArrayOps[Int]             = new ArrayOps.ofInt(xs)
  implicit def longArrayOps(xs: Array[Long]): ArrayOps[Long]          = new ArrayOps.ofLong(xs)
  implicit def refArrayOps[T <: AnyRef](xs: Array[T]): ArrayOps[T]    = new ArrayOps.ofRef[T](xs)
  implicit def shortArrayOps(xs: Array[Short]): ArrayOps[Short]       = new ArrayOps.ofShort(xs)
  implicit def unitArrayOps(xs: Array[Unit]): ArrayOps[Unit]          = new ArrayOps.ofUnit(xs)

  // "Autoboxing" and "Autounboxing" ---------------------------------------------------

  implicit def byte2Byte(x: Byte)           = java.lang.Byte.valueOf(x)
  implicit def short2Short(x: Short)        = java.lang.Short.valueOf(x)
  implicit def char2Character(x: Char)      = java.lang.Character.valueOf(x)
  implicit def int2Integer(x: Int)          = java.lang.Integer.valueOf(x)
  implicit def long2Long(x: Long)           = java.lang.Long.valueOf(x)
  implicit def float2Float(x: Float)        = java.lang.Float.valueOf(x)
  implicit def double2Double(x: Double)     = java.lang.Double.valueOf(x)
  implicit def boolean2Boolean(x: Boolean)  = java.lang.Boolean.valueOf(x)

  implicit def Byte2byte(x: java.lang.Byte): Byte             = x.byteValue
  implicit def Short2short(x: java.lang.Short): Short         = x.shortValue
  implicit def Character2char(x: java.lang.Character): Char   = x.charValue
  implicit def Integer2int(x: java.lang.Integer): Int         = x.intValue
  implicit def Long2long(x: java.lang.Long): Long             = x.longValue
  implicit def Float2float(x: java.lang.Float): Float         = x.floatValue
  implicit def Double2double(x: java.lang.Double): Double     = x.doubleValue
  implicit def Boolean2boolean(x: java.lang.Boolean): Boolean = x.booleanValue

  // Type Constraints --------------------------------------------------------------

  /**
   * An instance of `A <:< B` witnesses that `A` is a subtype of `B`.
   * Requiring an implicit argument of the type `A <:< B` encodes
   * the generalized constraint `A <: B`.
   *
   * @note we need a new type constructor `<:<` and evidence `conforms`,
   * as reusing `Function1` and `identity` leads to ambiguities in
   * case of type errors (`any2stringadd` is inferred)
   *
   * To constrain any abstract type T that's in scope in a method's
   * argument list (not just the method's own type parameters) simply
   * add an implicit argument of type `T <:< U`, where `U` is the required
   * upper bound; or for lower-bounds, use: `L <:< T`, where `L` is the
   * required lower bound.
   *
   * In part contributed by Jason Zaugg.
   */
  @implicitNotFound(msg = "Cannot prove that ${From} <:< ${To}.")
  sealed abstract class <:<[-From, +To] extends (From => To) with Serializable
  private[this] final val singleton_<:< = new <:<[Any,Any] { def apply(x: Any): Any = x }
  // The dollar prefix is to dodge accidental shadowing of this method
  // by a user-defined method of the same name (SI-7788).
  // The collections rely on this method.
  implicit def $conforms[A]: A <:< A = singleton_<:<.asInstanceOf[A <:< A]

  @deprecated("Use `implicitly[T <:< U]` or `identity` instead.", "2.11.0")
  def conforms[A]: A <:< A = $conforms[A]

  /** An instance of `A =:= B` witnesses that the types `A` and `B` are equal.
   *
   * @see `<:<` for expressing subtyping constraints
   */
  @implicitNotFound(msg = "Cannot prove that ${From} =:= ${To}.")
  sealed abstract class =:=[From, To] extends (From => To) with Serializable
  private[this] final val singleton_=:= = new =:=[Any,Any] { def apply(x: Any): Any = x }
  object =:= {
     implicit def tpEquals[A]: A =:= A = singleton_=:=.asInstanceOf[A =:= A]
  }

  /** A type for which there is always an implicit value.
   *  @see [[scala.Array$]], method `fallbackCanBuildFrom`
   */
  class DummyImplicit

  object DummyImplicit {

    /** An implicit value yielding a `DummyImplicit`.
     *   @see [[scala.Array$]], method `fallbackCanBuildFrom`
     */
    implicit def dummyImplicit: DummyImplicit = new DummyImplicit
  }
}

private[scala] trait DeprecatedPredef {
  self: Predef.type =>

  // Deprecated stubs for any who may have been calling these methods directly.
  @deprecated("Use `ArrowAssoc`", "2.11.0") def any2ArrowAssoc[A](x: A): ArrowAssoc[A]                                      = new ArrowAssoc(x)
  @deprecated("Use `Ensuring`", "2.11.0") def any2Ensuring[A](x: A): Ensuring[A]                                            = new Ensuring(x)
  @deprecated("Use `StringFormat`", "2.11.0") def any2stringfmt(x: Any): StringFormat[Any]                                  = new StringFormat(x)
  @deprecated("Use `Throwable` directly", "2.11.0") def exceptionWrapper(exc: Throwable)                                    = new RichException(exc)
  @deprecated("Use `SeqCharSequence`", "2.11.0") def seqToCharSequence(xs: scala.collection.IndexedSeq[Char]): CharSequence = new SeqCharSequence(xs)
  @deprecated("Use `ArrayCharSequence`", "2.11.0") def arrayToCharSequence(xs: Array[Char]): CharSequence                   = new ArrayCharSequence(xs)

  @deprecated("Use the method in `scala.io.StdIn`", "2.11.0") def readLine(): String                 = StdIn.readLine()
  @deprecated("Use the method in `scala.io.StdIn`", "2.11.0") def readLine(text: String, args: Any*) = StdIn.readLine(text, args: _*)
  @deprecated("Use the method in `scala.io.StdIn`", "2.11.0") def readBoolean()                      = StdIn.readBoolean()
  @deprecated("Use the method in `scala.io.StdIn`", "2.11.0") def readByte()                         = StdIn.readByte()
  @deprecated("Use the method in `scala.io.StdIn`", "2.11.0") def readShort()                        = StdIn.readShort()
  @deprecated("Use the method in `scala.io.StdIn`", "2.11.0") def readChar()                         = StdIn.readChar()
  @deprecated("Use the method in `scala.io.StdIn`", "2.11.0") def readInt()                          = StdIn.readInt()
  @deprecated("Use the method in `scala.io.StdIn`", "2.11.0") def readLong()                         = StdIn.readLong()
  @deprecated("Use the method in `scala.io.StdIn`", "2.11.0") def readFloat()                        = StdIn.readFloat()
  @deprecated("Use the method in `scala.io.StdIn`", "2.11.0") def readDouble()                       = StdIn.readDouble()
  @deprecated("Use the method in `scala.io.StdIn`", "2.11.0") def readf(format: String)              = StdIn.readf(format)
  @deprecated("Use the method in `scala.io.StdIn`", "2.11.0") def readf1(format: String)             = StdIn.readf1(format)
  @deprecated("Use the method in `scala.io.StdIn`", "2.11.0") def readf2(format: String)             = StdIn.readf2(format)
  @deprecated("Use the method in `scala.io.StdIn`", "2.11.0") def readf3(format: String)             = StdIn.readf3(format)
}

/** The `LowPriorityImplicits` class provides implicit values that
*  are valid in all Scala compilation units without explicit qualification,
*  but that are partially overridden by higher-priority conversions in object
*  `Predef`.
*
*  @author  Martin Odersky
*  @since 2.8
*/
// SI-7335 Parents of Predef are defined in the same compilation unit to avoid
// cyclic reference errors compiling the standard library *without* a previously
// compiled copy on the classpath.
private[scala] abstract class LowPriorityImplicits {
  import mutable.WrappedArray
  import immutable.WrappedString

  /** We prefer the java.lang.* boxed types to these wrappers in
   *  any potential conflicts.  Conflicts do exist because the wrappers
   *  need to implement ScalaNumber in order to have a symmetric equals
   *  method, but that implies implementing java.lang.Number as well.
   *
   *  Note - these are inlined because they are value classes, but
   *  the call to xxxWrapper is not eliminated even though it does nothing.
   *  Even inlined, every call site does a no-op retrieval of Predef's MODULE$
   *  because maybe loading Predef has side effects!
   */
  @inline implicit def byteWrapper(x: Byte)       = new runtime.RichByte(x)
  @inline implicit def shortWrapper(x: Short)     = new runtime.RichShort(x)
  @inline implicit def intWrapper(x: Int)         = new runtime.RichInt(x)
  @inline implicit def charWrapper(c: Char)       = new runtime.RichChar(c)
  @inline implicit def longWrapper(x: Long)       = new runtime.RichLong(x)
  @inline implicit def floatWrapper(x: Float)     = new runtime.RichFloat(x)
  @inline implicit def doubleWrapper(x: Double)   = new runtime.RichDouble(x)
  @inline implicit def booleanWrapper(x: Boolean) = new runtime.RichBoolean(x)

  implicit def genericWrapArray[T](xs: Array[T]): WrappedArray[T] =
    if (xs eq null) null
    else WrappedArray.make(xs)

  // Since the JVM thinks arrays are covariant, one 0-length Array[AnyRef]
  // is as good as another for all T <: AnyRef.  Instead of creating 100,000,000
  // unique ones by way of this implicit, let's share one.
  implicit def wrapRefArray[T <: AnyRef](xs: Array[T]): WrappedArray[T] = {
    if (xs eq null) null
    else if (xs.length == 0) WrappedArray.empty[T]
    else new WrappedArray.ofRef[T](xs)
  }

  implicit def wrapIntArray(xs: Array[Int]): WrappedArray[Int] = if (xs ne null) new WrappedArray.ofInt(xs) else null
  implicit def wrapDoubleArray(xs: Array[Double]): WrappedArray[Double] = if (xs ne null) new WrappedArray.ofDouble(xs) else null
  implicit def wrapLongArray(xs: Array[Long]): WrappedArray[Long] = if (xs ne null) new WrappedArray.ofLong(xs) else null
  implicit def wrapFloatArray(xs: Array[Float]): WrappedArray[Float] = if (xs ne null) new WrappedArray.ofFloat(xs) else null
  implicit def wrapCharArray(xs: Array[Char]): WrappedArray[Char] = if (xs ne null) new WrappedArray.ofChar(xs) else null
  implicit def wrapByteArray(xs: Array[Byte]): WrappedArray[Byte] = if (xs ne null) new WrappedArray.ofByte(xs) else null
  implicit def wrapShortArray(xs: Array[Short]): WrappedArray[Short] = if (xs ne null) new WrappedArray.ofShort(xs) else null
  implicit def wrapBooleanArray(xs: Array[Boolean]): WrappedArray[Boolean] = if (xs ne null) new WrappedArray.ofBoolean(xs) else null
  implicit def wrapUnitArray(xs: Array[Unit]): WrappedArray[Unit] = if (xs ne null) new WrappedArray.ofUnit(xs) else null

  implicit def wrapString(s: String): WrappedString = if (s ne null) new WrappedString(s) else null
  implicit def unwrapString(ws: WrappedString): String = if (ws ne null) ws.self else null

  implicit def fallbackStringCanBuildFrom[T]: CanBuildFrom[String, T, immutable.IndexedSeq[T]] =
    new CanBuildFrom[String, T, immutable.IndexedSeq[T]] {
      def apply(from: String) = immutable.IndexedSeq.newBuilder[T]
      def apply() = immutable.IndexedSeq.newBuilder[T]
    }
}

Other Scala source code examples

Here is a short list of links related to this Scala Predef.scala source code file:

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