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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2006, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id$
package scala;
object Seq {
/** builds a singleton sequence
* @author buraq
*/
def single[A](x:A) = new Seq[A] {
def length = 1;
def elements = Iterator.single(x);
override def isDefinedAt(x: Int): Boolean = (x == 0);
def apply(i:Int) = x; // caller's responsibility to check isDefinedAt
}
def view[A <% Ordered[A]](xs: Seq[A]): Ordered[Seq[A]] = new Ordered[Seq[A]] with Proxy {
def self: Any = xs;
def compareTo[B >: Seq[A] <% Ordered[B]](that: B): Int = that match {
case ys: Seq[A] =>
var res = 0;
val xsit = xs.elements;
val ysit = ys.elements;
while (xsit.hasNext && ysit.hasNext && (res == 0)) {
res = xsit.next compareTo ysit.next;
}
if (res != 0) res else if (xsit.hasNext) 1 else -1
case _ =>
-(that compareTo xs)
}
}
}
/** Class <code>Seq[A]</code> represents finite sequences of elements
* of type <code>A</code>.
*
* @author Martin Odersky
* @author Matthias Zenger
* @version 1.0, 16/07/2003
*/
mixin class Seq[+A] extends AnyRef with PartialFunction[Int, A] with Iterable[A] {
/** Returns the length of the sequence.
*
* @return the sequence length.
*/
def length: Int;
/** Returns the concatenation of two sequences.
*
* @return concatenation of this sequence with argument
* @author buraq
*/
def concat[B >: A](that:Seq[B]): Seq[B] = new Seq[B] {
def length = Seq.this.length + that.length;
def elements: Iterator[B] = Seq.this.elements.append(that.elements);
def apply(i:Int) = {
if(Seq.this.isDefinedAt(i))
Seq.this.apply(i)
else
that.apply(i - Seq.this.length);
}
}
/** Is this partial function defined for the index <code>x</code>?
*
* @return true, iff <code>x</code> is a legal sequence index.
*/
def isDefinedAt(x: Int): Boolean = (x >= 0) && (x < length);
/** Returns the index of the first occurence of the specified
* object in this sequence.
*
* @param elem element to search for.
* @return the index in this sequence of the first occurence of the specified
* element, or -1 if the sequence does not contain this element.
*/
def indexOf[B >: A](elem: B): Int = {
val it = elements;
var i = 0;
var found = false;
while (!found && it.hasNext) {
if (it.next == elem) {
found = true;
} else {
i = i + 1
}
}
if (found) i else -1;
}
/** Returns the index of the last occurence of the specified
* element in this sequence, or -1 if the sequence does not
* contain this element.
*
* @param elem element to search for.
* @return the index in this sequence of the last occurence of the
* specified element, or -1 if the sequence does not contain
* this element.
*/
def lastIndexOf[B >: A](elem: B): Int = {
var i = length;
var found = false;
while (!found && (i > 0)) {
i = i - 1;
if (this(i) == elem) {
found = true;
}
}
if (found) i else -1;
}
/** Returns the sub-sequence starting from index <code>n</code>.
*/
def take(n: Int): Seq[A] = subseq(0, n);
/** Returns a new sub-sequence that drops the first <code>n</code>
* elements of this sequence.
*/
def drop(n: Int): Seq[A] = subseq(n, length - n);
/** Returns a subsequence starting from index <code>from</code>
* consisting of <code>len</code> elements.
*/
def subseq(from: Int, len: Int): Seq[A] =
if ((from + len) <= length) new Seq[A] {
def apply(n: Int): A = Seq.this.apply(n + from);
def length: Int = len;
def elements: Iterator[A] = new Iterator[A] {
var i = from;
def hasNext = (i < (from + len));
def next = {
val res = Seq.this.apply(i);
i = i + 1;
res
}
}
} else
Predef.error("cannot create subsequence");
/** Fills the given array <code>xs</code> with the elements of
* this sequence starting at position <code>start</code>.
*
* @param xs the array to fill.
* @param start starting index.
* @return the given array <code>xs</code> filled with this list.
*/
def copyToArray[B >: A](xs: Array[B], start: Int): Array[B] = {
val it = elements;
var i = start;
while (it.hasNext) {
xs(i) = it.next;
i = i + 1;
}
xs
}
/** Transform this sequence into a list of all elements.
*
* @return a list which enumerates all elements of this sequence.
*/
def toList: List[A] = elements.toList;
/** Customizes the <code>toString</code> method.
*
* @return a string representation of this sequence.
*/
override def toString() = mkString(stringPrefix+"(", ",", ")")
/** Returns a string representation of this sequence. The resulting string
* begins with the string <code>start</code> and is finished by the string
* <code>end</code>. Inside, the string representations of elements (w.r.t.
* the method <code>toString()</code>) are separated by the string
* <code>sep</code>.
* <p/>
* Ex: <br/>
* <code>List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"</code>
*
* @param start starting string.
* @param sep separator string.
* @param end ending string.
* @return a string representation of this sequence.
*/
def mkString(start: String, sep: String, end: String): String = {
val buf = new StringBuffer()
buf.append(start)
val elems = elements
if (elems.hasNext) buf.append(elems.next)
while (elems.hasNext) {
buf.append(sep); buf.append(elems.next)
}
buf.append(end)
buf.toString
}
/** Defines the prefix of the string representation.
*/
protected def stringPrefix: String = "Seq";
}
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