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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2009, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id: Map.scala 16884 2009-01-09 16:52:09Z cunei $
package scalax.collection.generic
import collection.immutable.Set
import collection.mutable.ArrayBuffer
import annotation.unchecked.uncheckedVariance
/** <p>
* A map is a collection that maps each key to one or zero values.
* </p>
* <p>
* This trait provides a limited interface, only allowing reading of elements.
* There are two extensions of this trait, in packages
* <code><a href="mutable$content.html" target="contentFrame">
* scala.collection.mutable</a></code>
* and <code><a href="immutable$content.html" target="contentFrame">
* scala.collection.immutable</a></code>, which provide functionality for
* adding new key/value mappings to a map. The trait in the first package is
* for maps that are modified destructively, whereas the trait in
* the second package is for immutable maps which create a new map
* when something is added or removed from them.
* </p>
*
* @author Matthias Zenger
* @author Martin Odersky
* @version 1.2, 31/12/2006
*/
trait MapTemplate[A, B, +CC[A1, B1] <: Map[A1, B1] with MapTemplate[A1, B1, CC]]
extends PartialFunction[A, B]
with SizedIterable[(A, B)]
with Addable[CC[A, B], (A, B)]
with Subtractable[CC[A, B], A] {
self: CC[A, B] =>
def newBuilder[B]: Builder[SizedIterable, B] = new ArrayBuffer[B]
override def thisCC: CC[A, B] = this
/** This method returns a new map instance of the same class
* mapping keys of the same type to values of type <code>C</code>.
*/
def empty[C]: CC[A, C]
/** Compute the number of key-to-value mappings.
*
* @return the number of mappings
*/
def size: Int
/** Check if this map maps <code>key</code> to a value and return the
* value if it exists.
*
* @param key the key of the mapping of interest
* @return the value of the mapping, if it exists
*/
def get(key: A): Option[B]
/** Check if this map maps <code>key</code> to a value.
* Return that value if it exists, otherwise return <code>default</code>.
*/
def getOrElse[B2 >: B](key: A, default: => B2): B2 =
get(key) match {
case Some(v) => v
case None => default
}
/** Is this an empty map?
*
* @return <code>true</code> iff the map is empty.
*/
override def isEmpty: Boolean = size == 0
/** Retrieve the value which is associated with the given key. This
* method throws an exception if there is no mapping from the given
* key to a value.
*
* @param key the key
* @return the value associated with the given key.
*/
def apply(key: A): B = get(key) match {
case None => default(key)
case Some(value) => value
}
/** Is the given key mapped to a value by this map?
*
* @param key the key
* @return <code>true</code> iff there is a mapping for key in this map
*/
def contains(key: A): Boolean = get(key) match {
case None => false
case Some(_) => true
}
/** Does this map contain a mapping from the given key to a value?
*
* @param key the key
* @return <code>true</code> iff there is a mapping for key in this map
*/
def isDefinedAt(key: A) = contains(key)
/** Creates an iterator for all keys.
*
* @return an iterator over all keys.
*/
def keys: Iterator[A] = new Iterator[A] {
val iter = self.elements
def hasNext = iter.hasNext
def next = iter.next._1
}
/** @return the keys of this map as a set.
*/
def keySet: Set[A] = new Set[A] {
def size = self.size
def contains(key : A) = self.contains(key)
def elements = self.elements.map(_._1)
def + (elem: A): Set[A] = immutable.Set[A]() ++ this + elem
def - (elem: A): Set[A] = immutable.Set[A]() ++ this - elem
override def newBuilder[B]: Builder[Set, B] = Set.newBuilder[B]
}
/** Creates an iterator for a contained values.
*
* @return an iterator over all values.
*/
def values: Iterator[B] = new Iterator[B] {
val iter = self.elements
def hasNext = iter.hasNext
def next = iter.next._2
}
/** Creates a string representation for this map.
*
* @return a string showing all mappings
*/
override def toString() =
elements.toList.map(kv => kv._1 + " -> " + kv._2).mkString(stringPrefix + "(", ", ", ")")
/** The default value for the map, returned when a key is not found
* The method implemented here yields an error,
* but it might be overridden in subclasses.
*
* @param key the given key value
* @throws Predef.NoSuchElementException
*/
def default(key: A): B =
throw new NoSuchElementException("key not found: " + key)
/*
override def view: Map.View[A,B] = new Map.View[A, B] {
override def elements = self.elements
override def size = self.size
override def get(key: A): Option[B] = self.get(key)
}
*/
def filterKeys(p: A => Boolean) = new MapView[CC, A, B] {
val origin = self
override def foreach(f: ((A, B)) => Unit): Unit = for (kv <- self) if (p(kv._1)) f(kv)
def elements = self.elements.filter(kv => p(kv._1))
def size = { var sz = 0; foreach(_ => sz += 1); sz }
override def contains(key: A) = self.contains(key) && p(key)
def get(key: A) = if (!p(key)) None else self.get(key)
}
def mapElements[C](f: B => C) = new MapView[CC, A,C] {
val origin = self
override def foreach(g: ((A, C)) => Unit): Unit = for ((k, v) <- self) g((k, f(v)))
def elements = for ((k, v) <- self.elements) yield (k, f(v))
def size = self.size
override def contains(key: A) = self.contains(key)
def get(key: A) = self.get(key).map(f)
}
/** Defines the prefix of this object's <code>toString</code> representation.
*/
override def stringPrefix: String = "Map"
/** Add a key/value pair to this map.
* @param key the key
* @param value the value
* @return A new map with the new binding added to this map
*/
def update (key: A, value: B): CC[A, B]
/** Add a key/value pair to this map.
* @param kv the key/value pair.
* @return A new map with the new binding added to this map
*/
def + (kv: (A, B)): CC[A, B] = update(kv._1, kv._2)
/** Remove a key from this map
* @param key the key to be removed
* @return If the map does not contain a binding for <code>key</code>
* it is returned unchanged. Otherwise, return a new map
* without a binding for <code>key</code>
*/
def - (key: A): CC[A, B]
/** This function transforms all the values of mappings contained
* in this map with function <code>f</code>.
*
* @param f A function over keys and values
* @return the updated map
*/
def transform[C](f: (A, B) => C): CC[A, C] = {
var res = empty[C]
for ((key, value) <- this) res += ((key, f(key, value)))
res
}
/** Builds a new map with all key/value pairs of this map
* for which the predicate <code>p</code> returns <code>true</code>.
*
* @param p A predicate over key-value pairs
* @return the updated map
*/
override def filter(p: ((A, B)) => Boolean): CC[A, B] = {
var res = empty[B]
for (kv <- this)
if (p(kv)) res += kv
res
}
/** Removes all the mappings for which the predicate
* <code>p</code> returns <code>false</code>.
*
* @param p A predicate over key-value pairs
* @return the updated map
*/
override def remove(p: ((A, B)) => Boolean): CC[A, B] = {
var res = this
for (kv <- this)
if (!p(kv)) res -= kv._1
res
}
}
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