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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2006-2013, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.collection.immutable
import scala.collection.parallel.immutable.ParRange
/** The `Range` class represents integer values in range
* ''[start;end)'' with non-zero step value `step`.
* It's a special case of an indexed sequence.
* For example:
*
* {{{
* val r1 = 0 until 10
* val r2 = r1.start until r1.end by r1.step + 1
* println(r2.length) // = 5
* }}}
*
* @param start the start of this range.
* @param end the exclusive end of the range.
* @param step the step for the range.
*
* @author Martin Odersky
* @author Paul Phillips
* @version 2.8
* @since 2.5
* @see [[http://docs.scala-lang.org/overviews/collections/concrete-immutable-collection-classes.html#ranges "Scala's Collection Library overview"]]
* section on `Ranges` for more information.
*
* @define coll range
* @define mayNotTerminateInf
* @define willNotTerminateInf
* @define doesNotUseBuilders
* '''Note:''' this method does not use builders to construct a new range,
* and its complexity is O(1).
*/
@SerialVersionUID(7618862778670199309L)
class Range(val start: Int, val end: Int, val step: Int)
extends scala.collection.AbstractSeq[Int]
with IndexedSeq[Int]
with scala.collection.CustomParallelizable[Int, ParRange]
with Serializable
{
override def par = new ParRange(this)
private def gap = end.toLong - start.toLong
private def isExact = gap % step == 0
private def hasStub = isInclusive || !isExact
private def longLength = gap / step + ( if (hasStub) 1 else 0 )
// Check cannot be evaluated eagerly because we have a pattern where
// ranges are constructed like: "x to y by z" The "x to y" piece
// should not trigger an exception. So the calculation is delayed,
// which means it will not fail fast for those cases where failing was
// correct.
override final val isEmpty = (
(start > end && step > 0)
|| (start < end && step < 0)
|| (start == end && !isInclusive)
)
final val numRangeElements: Int = {
if (step == 0) throw new IllegalArgumentException("step cannot be 0.")
else if (isEmpty) 0
else {
val len = longLength
if (len > scala.Int.MaxValue) -1
else len.toInt
}
}
final val lastElement = start + (numRangeElements - 1) * step
final val terminalElement = start + numRangeElements * step
override def last = if (isEmpty) Nil.last else lastElement
override def min[A1 >: Int](implicit ord: Ordering[A1]): Int =
if (ord eq Ordering.Int) {
if (step > 0) start
else last
} else super.min(ord)
override def max[A1 >: Int](implicit ord: Ordering[A1]): Int =
if (ord eq Ordering.Int) {
if (step > 0) last
else start
} else super.max(ord)
protected def copy(start: Int, end: Int, step: Int): Range = new Range(start, end, step)
/** Create a new range with the `start` and `end` values of this range and
* a new `step`.
*
* @return a new range with a different step
*/
def by(step: Int): Range = copy(start, end, step)
def isInclusive = false
override def size = length
override def length = if (numRangeElements < 0) fail() else numRangeElements
private def description = "%d %s %d by %s".format(start, if (isInclusive) "to" else "until", end, step)
private def fail() = throw new IllegalArgumentException(description + ": seqs cannot contain more than Int.MaxValue elements.")
private def validateMaxLength() {
if (numRangeElements < 0)
fail()
}
def validateRangeBoundaries(f: Int => Any): Boolean = {
validateMaxLength()
start != Int.MinValue || end != Int.MinValue || {
var count = 0
var num = start
while (count < numRangeElements) {
f(num)
count += 1
num += step
}
false
}
}
final def apply(idx: Int): Int = {
validateMaxLength()
if (idx < 0 || idx >= numRangeElements) throw new IndexOutOfBoundsException(idx.toString)
else start + (step * idx)
}
@inline final override def foreach[@specialized(Unit) U](f: Int => U) {
if (validateRangeBoundaries(f)) {
var i = start
val terminal = terminalElement
val step = this.step
while (i != terminal) {
f(i)
i += step
}
}
}
/** Creates a new range containing the first `n` elements of this range.
*
* $doesNotUseBuilders
*
* @param n the number of elements to take.
* @return a new range consisting of `n` first elements.
*/
final override def take(n: Int): Range = (
if (n <= 0 || isEmpty) newEmptyRange(start)
else if (n >= numRangeElements) this
else new Range.Inclusive(start, locationAfterN(n - 1), step)
)
/** Creates a new range containing all the elements of this range except the first `n` elements.
*
* $doesNotUseBuilders
*
* @param n the number of elements to drop.
* @return a new range consisting of all the elements of this range except `n` first elements.
*/
final override def drop(n: Int): Range = (
if (n <= 0 || isEmpty) this
else if (n >= numRangeElements) newEmptyRange(end)
else copy(locationAfterN(n), end, step)
)
/** Creates a new range containing all the elements of this range except the last one.
*
* $doesNotUseBuilders
*
* @return a new range consisting of all the elements of this range except the last one.
*/
final override def init: Range = {
if (isEmpty)
Nil.init
dropRight(1)
}
/** Creates a new range containing all the elements of this range except the first one.
*
* $doesNotUseBuilders
*
* @return a new range consisting of all the elements of this range except the first one.
*/
final override def tail: Range = {
if (isEmpty)
Nil.tail
drop(1)
}
// Counts how many elements from the start meet the given test.
private def skipCount(p: Int => Boolean): Int = {
var current = start
var counted = 0
while (counted < numRangeElements && p(current)) {
counted += 1
current += step
}
counted
}
// Tests whether a number is within the endpoints, without testing
// whether it is a member of the sequence (i.e. when step > 1.)
private def isWithinBoundaries(elem: Int) = !isEmpty && (
(step > 0 && start <= elem && elem <= last ) ||
(step < 0 && last <= elem && elem <= start)
)
// Methods like apply throw exceptions on invalid n, but methods like take/drop
// are forgiving: therefore the checks are with the methods.
private def locationAfterN(n: Int) = start + (step * n)
// When one drops everything. Can't ever have unchecked operations
// like "end + 1" or "end - 1" because ranges involving Int.{ MinValue, MaxValue }
// will overflow. This creates an exclusive range where start == end
// based on the given value.
private def newEmptyRange(value: Int) = new Range(value, value, step)
final override def takeWhile(p: Int => Boolean): Range = take(skipCount(p))
final override def dropWhile(p: Int => Boolean): Range = drop(skipCount(p))
final override def span(p: Int => Boolean): (Range, Range) = splitAt(skipCount(p))
/** Creates a pair of new ranges, first consisting of elements before `n`, and the second
* of elements after `n`.
*
* $doesNotUseBuilders
*/
final override def splitAt(n: Int) = (take(n), drop(n))
/** Creates a new range consisting of the `length - n` last elements of the range.
*
* $doesNotUseBuilders
*/
final override def takeRight(n: Int): Range = drop(numRangeElements - n)
/** Creates a new range consisting of the initial `length - n` elements of the range.
*
* $doesNotUseBuilders
*/
final override def dropRight(n: Int): Range = take(numRangeElements - n)
/** Returns the reverse of this range.
*
* $doesNotUseBuilders
*/
final override def reverse: Range =
if (isEmpty) this
else new Range.Inclusive(last, start, -step)
/** Make range inclusive.
*/
def inclusive =
if (isInclusive) this
else new Range.Inclusive(start, end, step)
final def contains(x: Int) = isWithinBoundaries(x) && ((x - start) % step == 0)
final override def sum[B >: Int](implicit num: Numeric[B]): Int = {
if (isEmpty) 0
else if (numRangeElements == 1) head
else (numRangeElements.toLong * (head + last) / 2).toInt
}
override def toIterable = this
override def toSeq = this
override def equals(other: Any) = other match {
case x: Range =>
(x canEqual this) && (length == x.length) && (
isEmpty || // all empty sequences are equal
(start == x.start && last == x.last) // same length and same endpoints implies equality
)
case _ =>
super.equals(other)
}
/** Note: hashCode can't be overridden without breaking Seq's
* equals contract.
*/
override def toString() = {
val endStr = if (numRangeElements > Range.MAX_PRINT) ", ... )" else ")"
take(Range.MAX_PRINT).mkString("Range(", ", ", endStr)
}
}
/** A companion object for the `Range` class.
*/
object Range {
private[immutable] val MAX_PRINT = 512 // some arbitrary value
/** Counts the number of range elements.
* @pre step != 0
* If the size of the range exceeds Int.MaxValue, the
* result will be negative.
*/
def count(start: Int, end: Int, step: Int, isInclusive: Boolean): Int = {
if (step == 0)
throw new IllegalArgumentException("step cannot be 0.")
val isEmpty = (
if (start == end) !isInclusive
else if (start < end) step < 0
else step > 0
)
if (isEmpty) 0
else {
// Counts with Longs so we can recognize too-large ranges.
val gap: Long = end.toLong - start.toLong
val jumps: Long = gap / step
// Whether the size of this range is one larger than the
// number of full-sized jumps.
val hasStub = isInclusive || (gap % step != 0)
val result: Long = jumps + ( if (hasStub) 1 else 0 )
if (result > scala.Int.MaxValue) -1
else result.toInt
}
}
def count(start: Int, end: Int, step: Int): Int =
count(start, end, step, false)
class Inclusive(start: Int, end: Int, step: Int) extends Range(start, end, step) {
// override def par = new ParRange(this)
override def isInclusive = true
override protected def copy(start: Int, end: Int, step: Int): Range = new Inclusive(start, end, step)
}
/** Make a range from `start` until `end` (exclusive) with given step value.
* @note step != 0
*/
def apply(start: Int, end: Int, step: Int): Range = new Range(start, end, step)
/** Make a range from `start` until `end` (exclusive) with step value 1.
*/
def apply(start: Int, end: Int): Range = new Range(start, end, 1)
/** Make an inclusive range from `start` to `end` with given step value.
* @note step != 0
*/
def inclusive(start: Int, end: Int, step: Int): Range.Inclusive = new Inclusive(start, end, step)
/** Make an inclusive range from `start` to `end` with step value 1.
*/
def inclusive(start: Int, end: Int): Range.Inclusive = new Inclusive(start, end, 1)
// BigInt and Long are straightforward generic ranges.
object BigInt {
def apply(start: BigInt, end: BigInt, step: BigInt) = NumericRange(start, end, step)
def inclusive(start: BigInt, end: BigInt, step: BigInt) = NumericRange.inclusive(start, end, step)
}
object Long {
def apply(start: Long, end: Long, step: Long) = NumericRange(start, end, step)
def inclusive(start: Long, end: Long, step: Long) = NumericRange.inclusive(start, end, step)
}
// BigDecimal uses an alternative implementation of Numeric in which
// it pretends to be Integral[T] instead of Fractional[T]. See Numeric for
// details. The intention is for it to throw an exception anytime
// imprecision or surprises might result from anything, although this may
// not yet be fully implemented.
object BigDecimal {
implicit val bigDecAsIntegral = scala.math.Numeric.BigDecimalAsIfIntegral
def apply(start: BigDecimal, end: BigDecimal, step: BigDecimal) =
NumericRange(start, end, step)
def inclusive(start: BigDecimal, end: BigDecimal, step: BigDecimal) =
NumericRange.inclusive(start, end, step)
}
// Double works by using a BigDecimal under the hood for precise
// stepping, but mapping the sequence values back to doubles with
// .doubleValue. This constructs the BigDecimals by way of the
// String constructor (valueOf) instead of the Double one, which
// is necessary to keep 0.3d at 0.3 as opposed to
// 0.299999999999999988897769753748434595763683319091796875 or so.
object Double {
implicit val bigDecAsIntegral = scala.math.Numeric.BigDecimalAsIfIntegral
implicit val doubleAsIntegral = scala.math.Numeric.DoubleAsIfIntegral
def toBD(x: Double): BigDecimal = scala.math.BigDecimal valueOf x
def apply(start: Double, end: Double, step: Double) =
BigDecimal(toBD(start), toBD(end), toBD(step)) mapRange (_.doubleValue)
def inclusive(start: Double, end: Double, step: Double) =
BigDecimal.inclusive(toBD(start), toBD(end), toBD(step)) mapRange (_.doubleValue)
}
// As there is no appealing default step size for not-really-integral ranges,
// we offer a partially constructed object.
class Partial[T, U](f: T => U) {
def by(x: T): U = f(x)
}
// Illustrating genericity with Int Range, which should have the same behavior
// as the original Range class. However we leave the original Range
// indefinitely, for performance and because the compiler seems to bootstrap
// off it and won't do so with our parameterized version without modifications.
object Int {
def apply(start: Int, end: Int, step: Int) = NumericRange(start, end, step)
def inclusive(start: Int, end: Int, step: Int) = NumericRange.inclusive(start, end, step)
}
}
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