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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2006-2009, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id$
package scala
import collection.immutable.Vector
import collection.generic.VectorView
/** <p>
* <code>GenericRange</code> is a generified version of the
* <code>Range</code> class which works with arbitrary types.
* It must be supplied with Integral and Ordering implementations
* of the range type.
*
* Factories for likely types include Range.BigInt and Range.Long.
* Range.Int exists for completeness, but the Int-based scala.Range
* should be more performant.
* </p><pre>
* <b>val</b> r1 = new Range(0, 100, 1)
* <b>val</b> veryBig = Math.MAX_INT.toLong + 1
* <b>val</b> r2 = Range.Long(veryBig, veryBig + 100, 1)
* assert(r1 sameElements r2.map(_ - veryBig))
* </pre>
*
* @author Paul Phillips
* @version 2.8
*/
abstract class GenericRange[T]
(val start: T, val end: T, val step: T)
(implicit num: Integral[T], ord: Ordering[T])
extends VectorView[T, Vector[T]] with RangeToString[T] {
import num._
import ord._
// this lets us pretend all ranges are exclusive
val isInclusive: Boolean
private val trueEnd = if (isInclusive) end + one else end
// todo? - we could lift the length restriction by implementing a range as a sequence of
// subranges and limiting the subranges to MAX_INT. There's no other way around it because
// the generics we inherit assume integer-based indexing (as well they should.)
require(step !== zero)
require(genericLength <= fromInt(Math.MAX_INT), "Implementation restricts ranges to Math.MAX_INT elements.")
protected def underlying = Vector.empty[T]
/** Create a new range with the start and end values of this range and
* a new <code>step</code>.
*/
def by(step: T): GenericRange[T] =
if (isInclusive) GenericRange.inclusive(start, end, step)
else GenericRange(start, end, step)
override def foreach[U](f: T => U) {
var i = start
if (step > zero) {
while (i < trueEnd) {
f(i)
i = i + step
}
} else {
while (i > trueEnd) {
f(i)
i = i + step
}
}
}
lazy val genericLength: T = {
def plen(start: T, end: T, step: T) =
if (trueEnd <= start) zero
else (trueEnd - start - one) / step + one
if (step > zero) plen(start, trueEnd, step)
else plen(trueEnd, start, -step)
}
lazy val length: Int = toInt(genericLength)
// Since apply(Int) already exists, we are not allowed apply(T) since
// they erase to the same thing.
def apply(idx: Int): T = applyAt(fromInt(idx))
def applyAt(idx: T): T = {
if (idx < zero || idx >= genericLength) throw new IndexOutOfBoundsException(idx.toString)
start + idx * step
}
override def contains(_x: Any): Boolean = {
// XXX - can we avoid this cast and still have a contains method?
val x =
try { _x.asInstanceOf[T] }
catch { case _: ClassCastException => return false }
if (step > zero) start <= x && x < trueEnd
else start >= x && x > trueEnd
}
}
private[scala] trait RangeToString[T] extends VectorView[T, Vector[T]] {
// The default toString() tries to print every element and will exhaust memory
// if the Range is unduly large. This interacts poorly with the REPL.
override def toString() = {
val MAX_PRINT = 512 // some arbitrary value
val str = (this take MAX_PRINT).toString
if (length > MAX_PRINT) str.replaceAll("""\)$""", ", ...)")
else str
}
}
object GenericRange {
import Numeric._
import Ordering._
class Inclusive[T](start: T, end: T, step: T)(implicit num: Integral[T], ord: Ordering[T])
extends GenericRange(start, end, step)
{
val isInclusive = true
def exclusive: Exclusive[T] = new Exclusive(start, end, step)
}
class Exclusive[T](start: T, end: T, step: T)(implicit num: Integral[T], ord: Ordering[T])
extends GenericRange(start, end, step)
{
val isInclusive = false
def inclusive: Inclusive[T] = new Inclusive(start, end, step)
}
def apply[T](start: T, end: T, step: T)(implicit num: Integral[T], ord: Ordering[T]) =
new Exclusive(start, end, step)
def inclusive[T](start: T, end: T, step: T)(implicit num: Integral[T], ord: Ordering[T]) =
new Inclusive(start, end, step)
}
/** <p>
* The <code>Range</code> class represents integer values in range
* <code>[start;end)</code> with non-zero step value <code>step</code>.
* Sort of acts like a sequence also (supports length and contains).
* For example:
* </p><pre>
* <b>val</b> r1 = 0 until 10
* <b>val</b> r2 = r1.start until r1.end by r1.step + 1
* println(r2.length) // = 5
* </pre>
*
* @author Martin Odersky
* @version 2.8
*/
class Range(val start: Int, val end: Int, val step: Int)
extends VectorView[Int, Vector[Int]] with RangeToString[Int]
{
require(step != 0)
protected def underlying = Vector.empty[Int]
/** Create a new range with the start and end values of this range and
* a new <code>step</code>.
*/
def by(step: Int): Range = new Range(start, end, step)
final override def foreach[U](f: Int => U) {
var i = start
if (step > 0) {
while (i < end) {
f(i)
i += step
}
} else {
while (i > end) {
f(i)
i += step
}
}
}
lazy val length: Int = {
def plen(start: Int, end: Int, step: Int) =
if (end <= start) 0 else (end - start - 1) / step + 1
if (step > 0) plen(start, end, step)
else plen(end, start, -step)
}
@inline
final def apply(idx: Int): Int = {
if (idx < 0 || idx >= length) throw new IndexOutOfBoundsException(idx.toString)
start + idx * step
}
def contains(x: Int): Boolean =
if (step > 0) start <= x && x < end
else start >= x && x > end
def inclusive = Range.inclusive(start, end, step)
}
object Range {
/** @deprecated use Range.inclusive instead */
final class Inclusive(start: Int, end0: Int, step: Int)
extends Range(start, if (step > 0) end0 + 1 else end0 - 1, step) { self =>
override def by(step: Int): Range = new Inclusive(start, end0, step)
}
def apply(start: Int, end: Int, step: Int) =
new Range(start, end, step)
def inclusive(start: Int, end: Int, step: Int): Range =
new Range.Inclusive(start, end, step)
object BigInt {
def apply(start: BigInt, end: BigInt, step: BigInt) = GenericRange(start, end, step)
def inclusive(start: BigInt, end: BigInt, step: BigInt) = GenericRange.inclusive(start, end, step)
}
object Long {
def apply(start: Long, end: Long, step: Long) = GenericRange(start, end, step)
def inclusive(start: Long, end: Long, step: Long) = GenericRange.inclusive(start, end, step)
}
// 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) = GenericRange(start, end, step)
def inclusive(start: Int, end: Int, step: Int) = GenericRange.inclusive(start, end, step)
}
}
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