scala.Array.scala Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of scala-library Show documentation
Show all versions of scala-library Show documentation
Standard library for the Scala Programming Language
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2002-2013, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala
import scala.collection.generic._
import scala.collection.{ mutable, immutable }
import mutable.{ ArrayBuilder, ArraySeq }
import scala.compat.Platform.arraycopy
import scala.reflect.ClassTag
import scala.runtime.ScalaRunTime.{ array_apply, array_update }
/** Contains a fallback builder for arrays when the element type
* does not have a class tag. In that case a generic array is built.
*/
class FallbackArrayBuilding {
/** A builder factory that generates a generic array.
* Called instead of `Array.newBuilder` if the element type of an array
* does not have a class tag. Note that fallbackBuilder factory
* needs an implicit parameter (otherwise it would not be dominated in
* implicit search by `Array.canBuildFrom`). We make sure that
* implicit search is always successful.
*/
implicit def fallbackCanBuildFrom[T](implicit m: DummyImplicit): CanBuildFrom[Array[_], T, ArraySeq[T]] =
new CanBuildFrom[Array[_], T, ArraySeq[T]] {
def apply(from: Array[_]) = ArraySeq.newBuilder[T]
def apply() = ArraySeq.newBuilder[T]
}
}
/** Utility methods for operating on arrays.
* For example:
* {{{
* val a = Array(1, 2)
* val b = Array.ofDim[Int](2)
* val c = Array.concat(a, b)
* }}}
* where the array objects `a`, `b` and `c` have respectively the values
* `Array(1, 2)`, `Array(0, 0)` and `Array(1, 2, 0, 0)`.
*
* @author Martin Odersky
* @version 1.0
*/
object Array extends FallbackArrayBuilding {
val emptyBooleanArray = new Array[Boolean](0)
val emptyByteArray = new Array[Byte](0)
val emptyCharArray = new Array[Char](0)
val emptyDoubleArray = new Array[Double](0)
val emptyFloatArray = new Array[Float](0)
val emptyIntArray = new Array[Int](0)
val emptyLongArray = new Array[Long](0)
val emptyShortArray = new Array[Short](0)
val emptyObjectArray = new Array[Object](0)
implicit def canBuildFrom[T](implicit t: ClassTag[T]): CanBuildFrom[Array[_], T, Array[T]] =
new CanBuildFrom[Array[_], T, Array[T]] {
def apply(from: Array[_]) = ArrayBuilder.make[T]()(t)
def apply() = ArrayBuilder.make[T]()(t)
}
/**
* Returns a new [[scala.collection.mutable.ArrayBuilder]].
*/
def newBuilder[T](implicit t: ClassTag[T]): ArrayBuilder[T] = ArrayBuilder.make[T]()(t)
private def slowcopy(src : AnyRef,
srcPos : Int,
dest : AnyRef,
destPos : Int,
length : Int) {
var i = srcPos
var j = destPos
val srcUntil = srcPos + length
while (i < srcUntil) {
array_update(dest, j, array_apply(src, i))
i += 1
j += 1
}
}
/** Copy one array to another.
* Equivalent to Java's
* `System.arraycopy(src, srcPos, dest, destPos, length)`,
* except that this also works for polymorphic and boxed arrays.
*
* Note that the passed-in `dest` array will be modified by this call.
*
* @param src the source array.
* @param srcPos starting position in the source array.
* @param dest destination array.
* @param destPos starting position in the destination array.
* @param length the number of array elements to be copied.
*
* @see `java.lang.System#arraycopy`
*/
def copy(src: AnyRef, srcPos: Int, dest: AnyRef, destPos: Int, length: Int) {
val srcClass = src.getClass
if (srcClass.isArray && dest.getClass.isAssignableFrom(srcClass))
arraycopy(src, srcPos, dest, destPos, length)
else
slowcopy(src, srcPos, dest, destPos, length)
}
/** Returns an array of length 0 */
def empty[T: ClassTag]: Array[T] = new Array[T](0)
/** Creates an array with given elements.
*
* @param xs the elements to put in the array
* @return an array containing all elements from xs.
*/
// Subject to a compiler optimization in Cleanup.
// Array(e0, ..., en) is translated to { val a = new Array(3); a(i) = ei; a }
def apply[T: ClassTag](xs: T*): Array[T] = {
val array = new Array[T](xs.length)
var i = 0
for (x <- xs.iterator) { array(i) = x; i += 1 }
array
}
/** Creates an array of `Boolean` objects */
// Subject to a compiler optimization in Cleanup, see above.
def apply(x: Boolean, xs: Boolean*): Array[Boolean] = {
val array = new Array[Boolean](xs.length + 1)
array(0) = x
var i = 1
for (x <- xs.iterator) { array(i) = x; i += 1 }
array
}
/** Creates an array of `Byte` objects */
// Subject to a compiler optimization in Cleanup, see above.
def apply(x: Byte, xs: Byte*): Array[Byte] = {
val array = new Array[Byte](xs.length + 1)
array(0) = x
var i = 1
for (x <- xs.iterator) { array(i) = x; i += 1 }
array
}
/** Creates an array of `Short` objects */
// Subject to a compiler optimization in Cleanup, see above.
def apply(x: Short, xs: Short*): Array[Short] = {
val array = new Array[Short](xs.length + 1)
array(0) = x
var i = 1
for (x <- xs.iterator) { array(i) = x; i += 1 }
array
}
/** Creates an array of `Char` objects */
// Subject to a compiler optimization in Cleanup, see above.
def apply(x: Char, xs: Char*): Array[Char] = {
val array = new Array[Char](xs.length + 1)
array(0) = x
var i = 1
for (x <- xs.iterator) { array(i) = x; i += 1 }
array
}
/** Creates an array of `Int` objects */
// Subject to a compiler optimization in Cleanup, see above.
def apply(x: Int, xs: Int*): Array[Int] = {
val array = new Array[Int](xs.length + 1)
array(0) = x
var i = 1
for (x <- xs.iterator) { array(i) = x; i += 1 }
array
}
/** Creates an array of `Long` objects */
// Subject to a compiler optimization in Cleanup, see above.
def apply(x: Long, xs: Long*): Array[Long] = {
val array = new Array[Long](xs.length + 1)
array(0) = x
var i = 1
for (x <- xs.iterator) { array(i) = x; i += 1 }
array
}
/** Creates an array of `Float` objects */
// Subject to a compiler optimization in Cleanup, see above.
def apply(x: Float, xs: Float*): Array[Float] = {
val array = new Array[Float](xs.length + 1)
array(0) = x
var i = 1
for (x <- xs.iterator) { array(i) = x; i += 1 }
array
}
/** Creates an array of `Double` objects */
// Subject to a compiler optimization in Cleanup, see above.
def apply(x: Double, xs: Double*): Array[Double] = {
val array = new Array[Double](xs.length + 1)
array(0) = x
var i = 1
for (x <- xs.iterator) { array(i) = x; i += 1 }
array
}
/** Creates an array of `Unit` objects */
def apply(x: Unit, xs: Unit*): Array[Unit] = {
val array = new Array[Unit](xs.length + 1)
array(0) = x
var i = 1
for (x <- xs.iterator) { array(i) = x; i += 1 }
array
}
/** Creates array with given dimensions */
def ofDim[T: ClassTag](n1: Int): Array[T] =
new Array[T](n1)
/** Creates a 2-dimensional array */
def ofDim[T: ClassTag](n1: Int, n2: Int): Array[Array[T]] = {
val arr: Array[Array[T]] = (new Array[Array[T]](n1): Array[Array[T]])
for (i <- 0 until n1) arr(i) = new Array[T](n2)
arr
// tabulate(n1)(_ => ofDim[T](n2))
}
/** Creates a 3-dimensional array */
def ofDim[T: ClassTag](n1: Int, n2: Int, n3: Int): Array[Array[Array[T]]] =
tabulate(n1)(_ => ofDim[T](n2, n3))
/** Creates a 4-dimensional array */
def ofDim[T: ClassTag](n1: Int, n2: Int, n3: Int, n4: Int): Array[Array[Array[Array[T]]]] =
tabulate(n1)(_ => ofDim[T](n2, n3, n4))
/** Creates a 5-dimensional array */
def ofDim[T: ClassTag](n1: Int, n2: Int, n3: Int, n4: Int, n5: Int): Array[Array[Array[Array[Array[T]]]]] =
tabulate(n1)(_ => ofDim[T](n2, n3, n4, n5))
/** Concatenates all arrays into a single array.
*
* @param xss the given arrays
* @return the array created from concatenating `xss`
*/
def concat[T: ClassTag](xss: Array[T]*): Array[T] = {
val b = newBuilder[T]
b.sizeHint(xss.map(_.size).sum)
for (xs <- xss) b ++= xs
b.result
}
/** Returns an array that contains the results of some element computation a number
* of times.
*
* Note that this means that `elem` is computed a total of n times:
* {{{
* scala> Array.fill(3){ math.random }
* res3: Array[Double] = Array(0.365461167592537, 1.550395944913685E-4, 0.7907242137333306)
* }}}
*
* @param n the number of elements desired
* @param elem the element computation
* @return an Array of size n, where each element contains the result of computing
* `elem`.
*/
def fill[T: ClassTag](n: Int)(elem: => T): Array[T] = {
val b = newBuilder[T]
b.sizeHint(n)
var i = 0
while (i < n) {
b += elem
i += 1
}
b.result
}
/** Returns a two-dimensional array that contains the results of some element
* computation a number of times.
*
* @param n1 the number of elements in the 1st dimension
* @param n2 the number of elements in the 2nd dimension
* @param elem the element computation
*/
def fill[T: ClassTag](n1: Int, n2: Int)(elem: => T): Array[Array[T]] =
tabulate(n1)(_ => fill(n2)(elem))
/** Returns a three-dimensional array that contains the results of some element
* computation a number of times.
*
* @param n1 the number of elements in the 1st dimension
* @param n2 the number of elements in the 2nd dimension
* @param n3 the number of elements in the 3nd dimension
* @param elem the element computation
*/
def fill[T: ClassTag](n1: Int, n2: Int, n3: Int)(elem: => T): Array[Array[Array[T]]] =
tabulate(n1)(_ => fill(n2, n3)(elem))
/** Returns a four-dimensional array that contains the results of some element
* computation a number of times.
*
* @param n1 the number of elements in the 1st dimension
* @param n2 the number of elements in the 2nd dimension
* @param n3 the number of elements in the 3nd dimension
* @param n4 the number of elements in the 4th dimension
* @param elem the element computation
*/
def fill[T: ClassTag](n1: Int, n2: Int, n3: Int, n4: Int)(elem: => T): Array[Array[Array[Array[T]]]] =
tabulate(n1)(_ => fill(n2, n3, n4)(elem))
/** Returns a five-dimensional array that contains the results of some element
* computation a number of times.
*
* @param n1 the number of elements in the 1st dimension
* @param n2 the number of elements in the 2nd dimension
* @param n3 the number of elements in the 3nd dimension
* @param n4 the number of elements in the 4th dimension
* @param n5 the number of elements in the 5th dimension
* @param elem the element computation
*/
def fill[T: ClassTag](n1: Int, n2: Int, n3: Int, n4: Int, n5: Int)(elem: => T): Array[Array[Array[Array[Array[T]]]]] =
tabulate(n1)(_ => fill(n2, n3, n4, n5)(elem))
/** Returns an array containing values of a given function over a range of integer
* values starting from 0.
*
* @param n The number of elements in the array
* @param f The function computing element values
* @return A traversable consisting of elements `f(0),f(1), ..., f(n - 1)`
*/
def tabulate[T: ClassTag](n: Int)(f: Int => T): Array[T] = {
val b = newBuilder[T]
b.sizeHint(n)
var i = 0
while (i < n) {
b += f(i)
i += 1
}
b.result
}
/** Returns a two-dimensional array containing values of a given function
* over ranges of integer values starting from `0`.
*
* @param n1 the number of elements in the 1st dimension
* @param n2 the number of elements in the 2nd dimension
* @param f The function computing element values
*/
def tabulate[T: ClassTag](n1: Int, n2: Int)(f: (Int, Int) => T): Array[Array[T]] =
tabulate(n1)(i1 => tabulate(n2)(f(i1, _)))
/** Returns a three-dimensional array containing values of a given function
* over ranges of integer values starting from `0`.
*
* @param n1 the number of elements in the 1st dimension
* @param n2 the number of elements in the 2nd dimension
* @param n3 the number of elements in the 3rd dimension
* @param f The function computing element values
*/
def tabulate[T: ClassTag](n1: Int, n2: Int, n3: Int)(f: (Int, Int, Int) => T): Array[Array[Array[T]]] =
tabulate(n1)(i1 => tabulate(n2, n3)(f(i1, _, _)))
/** Returns a four-dimensional array containing values of a given function
* over ranges of integer values starting from `0`.
*
* @param n1 the number of elements in the 1st dimension
* @param n2 the number of elements in the 2nd dimension
* @param n3 the number of elements in the 3rd dimension
* @param n4 the number of elements in the 4th dimension
* @param f The function computing element values
*/
def tabulate[T: ClassTag](n1: Int, n2: Int, n3: Int, n4: Int)(f: (Int, Int, Int, Int) => T): Array[Array[Array[Array[T]]]] =
tabulate(n1)(i1 => tabulate(n2, n3, n4)(f(i1, _, _, _)))
/** Returns a five-dimensional array containing values of a given function
* over ranges of integer values starting from `0`.
*
* @param n1 the number of elements in the 1st dimension
* @param n2 the number of elements in the 2nd dimension
* @param n3 the number of elements in the 3rd dimension
* @param n4 the number of elements in the 4th dimension
* @param n5 the number of elements in the 5th dimension
* @param f The function computing element values
*/
def tabulate[T: ClassTag](n1: Int, n2: Int, n3: Int, n4: Int, n5: Int)(f: (Int, Int, Int, Int, Int) => T): Array[Array[Array[Array[Array[T]]]]] =
tabulate(n1)(i1 => tabulate(n2, n3, n4, n5)(f(i1, _, _, _, _)))
/** Returns an array containing a sequence of increasing integers in a range.
*
* @param start the start value of the array
* @param end the end value of the array, exclusive (in other words, this is the first value '''not''' returned)
* @return the array with values in range `start, start + 1, ..., end - 1`
* up to, but excluding, `end`.
*/
def range(start: Int, end: Int): Array[Int] = range(start, end, 1)
/** Returns an array containing equally spaced values in some integer interval.
*
* @param start the start value of the array
* @param end the end value of the array, exclusive (in other words, this is the first value '''not''' returned)
* @param step the increment value of the array (may not be zero)
* @return the array with values in `start, start + step, ...` up to, but excluding `end`
*/
def range(start: Int, end: Int, step: Int): Array[Int] = {
if (step == 0) throw new IllegalArgumentException("zero step")
val b = newBuilder[Int]
b.sizeHint(immutable.Range.count(start, end, step, false))
var i = start
while (if (step < 0) end < i else i < end) {
b += i
i += step
}
b.result
}
/** Returns an array containing repeated applications of a function to a start value.
*
* @param start the start value of the array
* @param len the number of elements returned by the array
* @param f the function that is repeatedly applied
* @return the array returning `len` values in the sequence `start, f(start), f(f(start)), ...`
*/
def iterate[T: ClassTag](start: T, len: Int)(f: T => T): Array[T] = {
val b = newBuilder[T]
if (len > 0) {
b.sizeHint(len)
var acc = start
var i = 1
b += acc
while (i < len) {
acc = f(acc)
i += 1
b += acc
}
}
b.result
}
/** Called in a pattern match like `{ case Array(x,y,z) => println('3 elements')}`.
*
* @param x the selector value
* @return sequence wrapped in a [[scala.Some]], if `x` is a Seq, otherwise `None`
*/
def unapplySeq[T](x: Array[T]): Option[IndexedSeq[T]] =
if (x == null) None else Some(x.toIndexedSeq)
// !!! the null check should to be necessary, but without it 2241 fails. Seems to be a bug
// in pattern matcher. @PP: I noted in #4364 I think the behavior is correct.
}
/** Arrays are mutable, indexed collections of values. `Array[T]` is Scala's representation
* for Java's `T[]`.
*
* {{{
* val numbers = Array(1, 2, 3, 4)
* val first = numbers(0) // read the first element
* numbers(3) = 100 // replace the 4th array element with 100
* val biggerNumbers = numbers.map(_ * 2) // multiply all numbers by two
* }}}
*
* Arrays make use of two common pieces of Scala syntactic sugar, shown on lines 2 and 3 of the above
* example code.
* Line 2 is translated into a call to `apply(Int)`, while line 3 is translated into a call to
* `update(Int, T)`.
*
* Two implicit conversions exist in [[scala.Predef]] that are frequently applied to arrays: a conversion
* to [[scala.collection.mutable.ArrayOps]] (shown on line 4 of the example above) and a conversion
* to [[scala.collection.mutable.WrappedArray]] (a subtype of [[scala.collection.Seq]]).
* Both types make available many of the standard operations found in the Scala collections API.
* The conversion to `ArrayOps` is temporary, as all operations defined on `ArrayOps` return an `Array`,
* while the conversion to `WrappedArray` is permanent as all operations return a `WrappedArray`.
*
* The conversion to `ArrayOps` takes priority over the conversion to `WrappedArray`. For instance,
* consider the following code:
*
* {{{
* val arr = Array(1, 2, 3)
* val arrReversed = arr.reverse
* val seqReversed : Seq[Int] = arr.reverse
* }}}
*
* Value `arrReversed` will be of type `Array[Int]`, with an implicit conversion to `ArrayOps` occurring
* to perform the `reverse` operation. The value of `seqReversed`, on the other hand, will be computed
* by converting to `WrappedArray` first and invoking the variant of `reverse` that returns another
* `WrappedArray`.
*
* @author Martin Odersky
* @version 1.0
* @see [[http://www.scala-lang.org/docu/files/ScalaReference.pdf Scala Language Specification]], for in-depth information on the transformations the Scala compiler makes on Arrays (Sections 6.6 and 6.15 respectively.)
* @see [[http://docs.scala-lang.org/sips/completed/scala-2-8-arrays.html "Scala 2.8 Arrays"]] the Scala Improvement Document detailing arrays since Scala 2.8.
* @see [[http://docs.scala-lang.org/overviews/collections/arrays.html "The Scala 2.8 Collections' API"]] section on `Array` by Martin Odersky for more information.
* @define coll array
* @define Coll `Array`
* @define orderDependent
* @define orderDependentFold
* @define mayNotTerminateInf
* @define willNotTerminateInf
* @define collectExample
* @define undefinedorder
* @define thatinfo the class of the returned collection. In the standard library configuration,
* `That` is either `Array[B]` if an ClassTag is available for B or `ArraySeq[B]` otherwise.
* @define zipthatinfo $thatinfo
* @define bfinfo an implicit value of class `CanBuildFrom` which determines the result class `That` from the current
* representation type `Repr` and the new element type `B`.
*/
final class Array[T](_length: Int) extends java.io.Serializable with java.lang.Cloneable {
/** The length of the array */
def length: Int = throw new Error()
/** The element at given index.
*
* Indices start at `0`; `xs.apply(0)` is the first element of array `xs`.
* Note the indexing syntax `xs(i)` is a shorthand for `xs.apply(i)`.
*
* @param i the index
* @return the element at the given index
* @throws ArrayIndexOutOfBoundsException if `i < 0` or `length <= i`
*/
def apply(i: Int): T = throw new Error()
/** Update the element at given index.
*
* Indices start at `0`; `xs.update(i, x)` replaces the i^th^ element in the array.
* Note the syntax `xs(i) = x` is a shorthand for `xs.update(i, x)`.
*
* @param i the index
* @param x the value to be written at index `i`
* @throws ArrayIndexOutOfBoundsException if `i < 0` or `length <= i`
*/
def update(i: Int, x: T) { throw new Error() }
/** Clone the Array.
*
* @return A clone of the Array.
*/
override def clone(): Array[T] = throw new Error()
}