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Standard library for the Scala Programming Language
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2013, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.collection
package mutable
/** The canonical builder for immutable maps, working with the map's `+` method
* to add new elements.
* Collections are built from their `empty` element using this + method.
*
* @tparam A Type of the keys for the map this builder creates.
* @tparam B Type of the values for the map this builder creates.
* @tparam Coll The type of the actual collection this builder builds.
* @param empty The empty element of the collection.
*
* @since 2.8
*/
class MapBuilder[A, B, Coll <: scala.collection.GenMap[A, B] with scala.collection.GenMapLike[A, B, Coll]](empty: Coll)
extends Builder[(A, B), Coll] {
protected var elems: Coll = empty
def +=(x: (A, B)): this.type = {
elems = (elems + x).asInstanceOf[Coll]
// the cast is necessary because right now we cannot enforce statically that
// for every map of type Coll, `+` yields again a Coll. With better support
// for hk-types we might be able to enforce this in the future, though.
this
}
def clear() { elems = empty }
def result: Coll = elems
}