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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2010, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.collection
package immutable
import generic._
/**
* A generic template for immutable maps from keys of type `A`
* to values of type `B`.
* To implement a concrete map, you need to provide implementations of the
* following methods (where `This` is the type of the actual map implementation):
*
* {{{
* def get(key: A): Option[B]
* def iterator: Iterator[(A, B)]
* def + [B1 >: B](kv: (A, B)): Map[A, B1]
* def - (key: A): This
* }}}
*
* If you wish that transformer methods like `take`, `drop`, `filter` return the
* same kind of map, you should also override:
*
* {{{
* def empty: This
* }}}
*
* It is also good idea to override methods `foreach` and
* `size` for efficiency.
*
* @param A the type of the keys contained in this collection.
* @param B the type of the values associated with the keys.
* @param This The type of the actual map implementation.
*
* @author Martin Odersky
* @version 2.8
* @since 2.8
* @define Coll immutable.Map
* @define coll immutable map
*/
trait MapLike[A, +B, +This <: MapLike[A, B, This] with Map[A, B]]
extends scala.collection.MapLike[A, B, This]
{ self =>
import scala.collection.Traversable
/** A new immutable map containing updating this map with a given key/value mapping.
* @param key the key
* @param value the value
* @return A new map with the new key/value mapping
*/
override def updated [B1 >: B](key: A, value: B1): immutable.Map[A, B1] = this + ((key, value))
/** Add a key/value pair to this map, returning a new map.
* @param kv the key/value pair.
* @return A new map with the new binding added to this map.
*/
def + [B1 >: B] (kv: (A, B1)): immutable.Map[A, B1]
/** Adds two or more elements to this collection and returns
* a new collection.
*
* @param elem1 the first element to add.
* @param elem2 the second element to add.
* @param elems the remaining elements to add.
* @return A new map with the new bindings added to this map.
*/
override def + [B1 >: B] (elem1: (A, B1), elem2: (A, B1), elems: (A, B1) *): immutable.Map[A, B1] =
this + elem1 + elem2 ++ elems
/** Adds a number of elements provided by a traversable object
* and returns a new collection with the added elements.
*
* @param xs the traversable object consisting of key-value pairs.
* @return a new immutable map with the bindings of this map and those from `xs`.
*/
override def ++[B1 >: B](xs: TraversableOnce[(A, B1)]): immutable.Map[A, B1] =
((repr: immutable.Map[A, B1]) /: xs) (_ + _)
/** Filters this map by retaining only keys satisfying a predicate.
* @param p the predicate used to test keys
* @return an immutable map consisting only of those key value pairs of this map where the key satisfies
* the predicate `p`. The resulting map wraps the original map without copying any elements.
*/
override def filterKeys(p: A => Boolean): Map[A, B] = new DefaultMap[A, B] {
override def foreach[C](f: ((A, B)) => C): Unit = for (kv <- self) if (p(kv._1)) f(kv)
def iterator = self.iterator.filter(kv => p(kv._1))
override def contains(key: A) = self.contains(key) && p(key)
def get(key: A) = if (!p(key)) None else self.get(key)
}
/** Transforms this map by applying a function to every retrieved value.
* @param f the function used to transform values of this map.
* @return a map view which maps every key of this map
* to `f(this(key))`. The resulting map wraps the original map without copying any elements.
*/
override def mapValues[C](f: B => C): Map[A, C] = new DefaultMap[A, C] {
override def foreach[D](g: ((A, C)) => D): Unit = for ((k, v) <- self) g((k, f(v)))
def iterator = for ((k, v) <- self.iterator) yield (k, f(v))
override def size = self.size
override def contains(key: A) = self.contains(key)
def get(key: A) = self.get(key).map(f)
}
/** This function transforms all the values of mappings contained
* in this map with function `f`.
*
* @param f A function over keys and values
* @return the updated map
*/
def transform[C, That](f: (A, B) => C)(implicit bf: CanBuildFrom[This, (A, C), That]): That = {
val b = bf(repr)
for ((key, value) <- this) b += ((key, f(key, value)))
b.result
}
@deprecated("use `updated' instead")
def update[B1 >: B](key: A, value: B1): immutable.Map[A, B1] = updated(key, value).asInstanceOf[immutable.Map[A, B1]]
}
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