CodeMirror: C-like mode

diff --git a/rhodecode/public/js/mode/clike/scala.html b/rhodecode/public/js/mode/clike/scala.html new file mode 100644 --- /dev/null +++ b/rhodecode/public/js/mode/clike/scala.html @@ -0,0 +1,767 @@ + + + + + CodeMirror: C-like mode + + + + + + + + + +

+
+  /*                     __                                               *\
+  **     ________ ___   / /  ___     Scala API                            **
+  **    / __/ __// _ | / /  / _ |    (c) 2003-2011, LAMP/EPFL             **
+  **  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
+  ** /____/\___/_/ |_/____/_/ | |                                         **
+  **                          |/                                          **
+  \*                                                                      */
+
+  package scala.collection
+
+  import generic._
+  import mutable.{ Builder, ListBuffer }
+  import annotation.{tailrec, migration, bridge}
+  import annotation.unchecked.{ uncheckedVariance => uV }
+  import parallel.ParIterable
+
+  /** A template trait for traversable collections of type `Traversable[A]`.
+   *  
+   *  $traversableInfo
+   *  @define mutability
+   *  @define traversableInfo
+   *  This is a base trait of all kinds of $mutability Scala collections. It
+   *  implements the behavior common to all collections, in terms of a method
+   *  `foreach` with signature:
+   * {{{
+   *     def foreach[U](f: Elem => U): Unit
+   * }}}
+   *  Collection classes mixing in this trait provide a concrete 
+   *  `foreach` method which traverses all the
+   *  elements contained in the collection, applying a given function to each.
+   *  They also need to provide a method `newBuilder`
+   *  which creates a builder for collections of the same kind.
+   *  
+   *  A traversable class might or might not have two properties: strictness
+   *  and orderedness. Neither is represented as a type.
+   *  
+   *  The instances of a strict collection class have all their elements
+   *  computed before they can be used as values. By contrast, instances of
+   *  a non-strict collection class may defer computation of some of their
+   *  elements until after the instance is available as a value.
+   *  A typical example of a non-strict collection class is a
+   *  <a href="../immutable/Stream.html" target="ContentFrame">
+   *  `scala.collection.immutable.Stream`</a>.
+   *  A more general class of examples are `TraversableViews`.
+   *  
+   *  If a collection is an instance of an ordered collection class, traversing
+   *  its elements with `foreach` will always visit elements in the
+   *  same order, even for different runs of the program. If the class is not
+   *  ordered, `foreach` can visit elements in different orders for
+   *  different runs (but it will keep the same order in the same run).'
+   * 
+   *  A typical example of a collection class which is not ordered is a
+   *  `HashMap` of objects. The traversal order for hash maps will
+   *  depend on the hash codes of its elements, and these hash codes might
+   *  differ from one run to the next. By contrast, a `LinkedHashMap`
+   *  is ordered because it's `foreach` method visits elements in the
+   *  order they were inserted into the `HashMap`.
+   *
+   *  @author Martin Odersky
+   *  @version 2.8
+   *  @since   2.8
+   *  @tparam A    the element type of the collection
+   *  @tparam Repr the type of the actual collection containing the elements.
+   *
+   *  @define Coll Traversable
+   *  @define coll traversable collection
+   */
+  trait TraversableLike[+A, +Repr] extends HasNewBuilder[A, Repr] 
+                                      with FilterMonadic[A, Repr]
+                                      with TraversableOnce[A]
+                                      with GenTraversableLike[A, Repr]
+                                      with Parallelizable[A, ParIterable[A]]
+  {
+    self =>
+
+    import Traversable.breaks._
+
+    /** The type implementing this traversable */
+    protected type Self = Repr
+
+    /** The collection of type $coll underlying this `TraversableLike` object.
+     *  By default this is implemented as the `TraversableLike` object itself,
+     *  but this can be overridden.
+     */
+    def repr: Repr = this.asInstanceOf[Repr]
+
+    /** The underlying collection seen as an instance of `$Coll`.
+     *  By default this is implemented as the current collection object itself,
+     *  but this can be overridden.
+     */
+    protected[this] def thisCollection: Traversable[A] = this.asInstanceOf[Traversable[A]]
+
+    /** A conversion from collections of type `Repr` to `$Coll` objects.
+     *  By default this is implemented as just a cast, but this can be overridden.
+     */
+    protected[this] def toCollection(repr: Repr): Traversable[A] = repr.asInstanceOf[Traversable[A]]
+
+    /** Creates a new builder for this collection type.
+     */
+    protected[this] def newBuilder: Builder[A, Repr]
+
+    protected[this] def parCombiner = ParIterable.newCombiner[A]
+
+    /** Applies a function `f` to all elements of this $coll.
+     *  
+     *    Note: this method underlies the implementation of most other bulk operations.
+     *    It's important to implement this method in an efficient way.
+     *  
+     *
+     *  @param  f   the function that is applied for its side-effect to every element.
+     *              The result of function `f` is discarded.
+     *              
+     *  @tparam  U  the type parameter describing the result of function `f`. 
+     *              This result will always be ignored. Typically `U` is `Unit`,
+     *              but this is not necessary.
+     *
+     *  @usecase def foreach(f: A => Unit): Unit
+     */
+    def foreach[U](f: A => U): Unit
+
+    /** Tests whether this $coll is empty.
+     *
+     *  @return    `true` if the $coll contain no elements, `false` otherwise.
+     */
+    def isEmpty: Boolean = {
+      var result = true
+      breakable {
+        for (x <- this) {
+          result = false
+          break
+        }
+      }
+      result
+    }
+
+    /** Tests whether this $coll is known to have a finite size.
+     *  All strict collections are known to have finite size. For a non-strict collection
+     *  such as `Stream`, the predicate returns `true` if all elements have been computed.
+     *  It returns `false` if the stream is not yet evaluated to the end.
+     *
+     *  Note: many collection methods will not work on collections of infinite sizes. 
+     *
+     *  @return  `true` if this collection is known to have finite size, `false` otherwise.
+     */
+    def hasDefiniteSize = true
+
+    def ++[B >: A, That](that: GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
+      val b = bf(repr)
+      if (that.isInstanceOf[IndexedSeqLike[_, _]]) b.sizeHint(this, that.seq.size)
+      b ++= thisCollection
+      b ++= that.seq
+      b.result
+    }
+
+    @bridge
+    def ++[B >: A, That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That =
+      ++(that: GenTraversableOnce[B])(bf)
+
+    /** Concatenates this $coll with the elements of a traversable collection.
+     *  It differs from ++ in that the right operand determines the type of the
+     *  resulting collection rather than the left one.
+     * 
+     *  @param that   the traversable to append.
+     *  @tparam B     the element type of the returned collection. 
+     *  @tparam That  $thatinfo
+     *  @param bf     $bfinfo
+     *  @return       a new collection of type `That` which contains all elements
+     *                of this $coll followed by all elements of `that`.
+     * 
+     *  @usecase def ++:[B](that: TraversableOnce[B]): $Coll[B]
+     *  
+     *  @return       a new $coll which contains all elements of this $coll
+     *                followed by all elements of `that`.
+     */
+    def ++:[B >: A, That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
+      val b = bf(repr)
+      if (that.isInstanceOf[IndexedSeqLike[_, _]]) b.sizeHint(this, that.size)
+      b ++= that
+      b ++= thisCollection
+      b.result
+    }
+
+    /** This overload exists because: for the implementation of ++: we should reuse
+     *  that of ++ because many collections override it with more efficient versions.
+     *  Since TraversableOnce has no '++' method, we have to implement that directly,
+     *  but Traversable and down can use the overload.
+     */
+    def ++:[B >: A, That](that: Traversable[B])(implicit bf: CanBuildFrom[Repr, B, That]): That =
+      (that ++ seq)(breakOut)
+
+    def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
+      val b = bf(repr)
+      b.sizeHint(this) 
+      for (x <- this) b += f(x)
+      b.result
+    }
+
+    def flatMap[B, That](f: A => GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
+      val b = bf(repr)
+      for (x <- this) b ++= f(x).seq
+      b.result
+    }
+
+    /** Selects all elements of this $coll which satisfy a predicate.
+     *
+     *  @param p     the predicate used to test elements.
+     *  @return      a new $coll consisting of all elements of this $coll that satisfy the given
+     *               predicate `p`. The order of the elements is preserved.
+     */
+    def filter(p: A => Boolean): Repr = {
+      val b = newBuilder
+      for (x <- this) 
+        if (p(x)) b += x
+      b.result
+    }
+
+    /** Selects all elements of this $coll which do not satisfy a predicate.
+     *
+     *  @param p     the predicate used to test elements.
+     *  @return      a new $coll consisting of all elements of this $coll that do not satisfy the given
+     *               predicate `p`. The order of the elements is preserved.
+     */
+    def filterNot(p: A => Boolean): Repr = filter(!p(_))
+
+    def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
+      val b = bf(repr)
+      for (x <- this) if (pf.isDefinedAt(x)) b += pf(x)
+      b.result
+    }
+
+    /** Builds a new collection by applying an option-valued function to all
+     *  elements of this $coll on which the function is defined.
+     *
+     *  @param f      the option-valued function which filters and maps the $coll.
+     *  @tparam B     the element type of the returned collection.
+     *  @tparam That  $thatinfo
+     *  @param bf     $bfinfo
+     *  @return       a new collection of type `That` resulting from applying the option-valued function
+     *                `f` to each element and collecting all defined results.
+     *                The order of the elements is preserved.
+     *
+     *  @usecase def filterMap[B](f: A => Option[B]): $Coll[B]
+     *  
+     *  @param pf     the partial function which filters and maps the $coll.
+     *  @return       a new $coll resulting from applying the given option-valued function
+     *                `f` to each element and collecting all defined results.
+     *                The order of the elements is preserved.
+    def filterMap[B, That](f: A => Option[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
+      val b = bf(repr)
+      for (x <- this) 
+        f(x) match {
+          case Some(y) => b += y
+          case _ =>
+        }
+      b.result
+    }
+     */
+
+    /** Partitions this $coll in two ${coll}s according to a predicate.
+     *
+     *  @param p the predicate on which to partition.
+     *  @return  a pair of ${coll}s: the first $coll consists of all elements that 
+     *           satisfy the predicate `p` and the second $coll consists of all elements
+     *           that don't. The relative order of the elements in the resulting ${coll}s
+     *           is the same as in the original $coll.
+     */
+    def partition(p: A => Boolean): (Repr, Repr) = {
+      val l, r = newBuilder
+      for (x <- this) (if (p(x)) l else r) += x
+      (l.result, r.result)
+    }
+
+    def groupBy[K](f: A => K): immutable.Map[K, Repr] = {
+      val m = mutable.Map.empty[K, Builder[A, Repr]]
+      for (elem <- this) {
+        val key = f(elem)
+        val bldr = m.getOrElseUpdate(key, newBuilder)
+        bldr += elem
+      }
+      val b = immutable.Map.newBuilder[K, Repr]
+      for ((k, v) <- m)
+        b += ((k, v.result))
+
+      b.result
+    }
+
+    /** Tests whether a predicate holds for all elements of this $coll.
+     *
+     *  $mayNotTerminateInf
+     *
+     *  @param   p     the predicate used to test elements.
+     *  @return        `true` if the given predicate `p` holds for all elements
+     *                 of this $coll, otherwise `false`.
+     */
+    def forall(p: A => Boolean): Boolean = {
+      var result = true
+      breakable {
+        for (x <- this)
+          if (!p(x)) { result = false; break }
+      }
+      result
+    }
+
+    /** Tests whether a predicate holds for some of the elements of this $coll.
+     *
+     *  $mayNotTerminateInf
+     *
+     *  @param   p     the predicate used to test elements.
+     *  @return        `true` if the given predicate `p` holds for some of the
+     *                 elements of this $coll, otherwise `false`.
+     */
+    def exists(p: A => Boolean): Boolean = {
+      var result = false
+      breakable {
+        for (x <- this)
+          if (p(x)) { result = true; break }
+      }
+      result
+    }
+
+    /** Finds the first element of the $coll satisfying a predicate, if any.
+     * 
+     *  $mayNotTerminateInf
+     *  $orderDependent
+     *
+     *  @param p    the predicate used to test elements.
+     *  @return     an option value containing the first element in the $coll
+     *              that satisfies `p`, or `None` if none exists.
+     */
+    def find(p: A => Boolean): Option[A] = {
+      var result: Option[A] = None
+      breakable {
+        for (x <- this)
+          if (p(x)) { result = Some(x); break }
+      }
+      result
+    }
+
+    def scan[B >: A, That](z: B)(op: (B, B) => B)(implicit cbf: CanBuildFrom[Repr, B, That]): That = scanLeft(z)(op)
+
+    def scanLeft[B, That](z: B)(op: (B, A) => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
+      val b = bf(repr)
+      b.sizeHint(this, 1)
+      var acc = z
+      b += acc
+      for (x <- this) { acc = op(acc, x); b += acc }
+      b.result
+    }
+
+    @migration(2, 9,
+      "This scanRight definition has changed in 2.9.\n" +
+      "The previous behavior can be reproduced with scanRight.reverse."
+    )
+    def scanRight[B, That](z: B)(op: (A, B) => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
+      var scanned = List(z)
+      var acc = z
+      for (x <- reversed) {
+        acc = op(x, acc)
+        scanned ::= acc
+      }
+      val b = bf(repr)
+      for (elem <- scanned) b += elem
+      b.result
+    }
+
+    /** Selects the first element of this $coll.
+     *  $orderDependent
+     *  @return  the first element of this $coll.
+     *  @throws `NoSuchElementException` if the $coll is empty.
+     */
+    def head: A = {
+      var result: () => A = () => throw new NoSuchElementException
+      breakable {
+        for (x <- this) {
+          result = () => x
+          break
+        }
+      }
+      result()
+    }
+
+    /** Optionally selects the first element.
+     *  $orderDependent
+     *  @return  the first element of this $coll if it is nonempty, `None` if it is empty.
+     */
+    def headOption: Option[A] = if (isEmpty) None else Some(head)
+
+    /** Selects all elements except the first.
+     *  $orderDependent
+     *  @return  a $coll consisting of all elements of this $coll
+     *           except the first one.
+     *  @throws `UnsupportedOperationException` if the $coll is empty.
+     */ 
+    override def tail: Repr = {
+      if (isEmpty) throw new UnsupportedOperationException("empty.tail")
+      drop(1)
+    }
+
+    /** Selects the last element.
+      * $orderDependent
+      * @return The last element of this $coll.
+      * @throws NoSuchElementException If the $coll is empty.
+      */
+    def last: A = {
+      var lst = head
+      for (x <- this)
+        lst = x
+      lst
+    }
+
+    /** Optionally selects the last element.
+     *  $orderDependent
+     *  @return  the last element of this $coll$ if it is nonempty, `None` if it is empty.
+     */
+    def lastOption: Option[A] = if (isEmpty) None else Some(last)
+
+    /** Selects all elements except the last.
+     *  $orderDependent
+     *  @return  a $coll consisting of all elements of this $coll
+     *           except the last one.
+     *  @throws `UnsupportedOperationException` if the $coll is empty.
+     */
+    def init: Repr = {
+      if (isEmpty) throw new UnsupportedOperationException("empty.init")
+      var lst = head
+      var follow = false
+      val b = newBuilder
+      b.sizeHint(this, -1)
+      for (x <- this.seq) {
+        if (follow) b += lst
+        else follow = true
+        lst = x
+      }
+      b.result
+    }
+
+    def take(n: Int): Repr = slice(0, n)
+
+    def drop(n: Int): Repr = 
+      if (n <= 0) {
+        val b = newBuilder
+        b.sizeHint(this)
+        b ++= thisCollection result
+      }
+      else sliceWithKnownDelta(n, Int.MaxValue, -n)
+
+    def slice(from: Int, until: Int): Repr = sliceWithKnownBound(math.max(from, 0), until)
+
+    // Precondition: from >= 0, until > 0, builder already configured for building.
+    private[this] def sliceInternal(from: Int, until: Int, b: Builder[A, Repr]): Repr = {
+      var i = 0
+      breakable {
+        for (x <- this.seq) {
+          if (i >= from) b += x
+          i += 1
+          if (i >= until) break
+        }
+      }
+      b.result
+    }
+    // Precondition: from >= 0
+    private[scala] def sliceWithKnownDelta(from: Int, until: Int, delta: Int): Repr = {
+      val b = newBuilder
+      if (until <= from) b.result
+      else {
+        b.sizeHint(this, delta)
+        sliceInternal(from, until, b)
+      }
+    }
+    // Precondition: from >= 0
+    private[scala] def sliceWithKnownBound(from: Int, until: Int): Repr = {
+      val b = newBuilder
+      if (until <= from) b.result
+      else {
+        b.sizeHintBounded(until - from, this)      
+        sliceInternal(from, until, b)
+      }
+    }
+
+    def takeWhile(p: A => Boolean): Repr = {
+      val b = newBuilder
+      breakable {
+        for (x <- this) {
+          if (!p(x)) break
+          b += x
+        }
+      }
+      b.result
+    }
+
+    def dropWhile(p: A => Boolean): Repr = {
+      val b = newBuilder
+      var go = false
+      for (x <- this) {
+        if (!p(x)) go = true
+        if (go) b += x
+      }
+      b.result
+    }
+
+    def span(p: A => Boolean): (Repr, Repr) = {
+      val l, r = newBuilder
+      var toLeft = true
+      for (x <- this) {
+        toLeft = toLeft && p(x)
+        (if (toLeft) l else r) += x
+      }
+      (l.result, r.result)
+    }
+
+    def splitAt(n: Int): (Repr, Repr) = {
+      val l, r = newBuilder
+      l.sizeHintBounded(n, this)
+      if (n >= 0) r.sizeHint(this, -n)
+      var i = 0
+      for (x <- this) {
+        (if (i < n) l else r) += x
+        i += 1
+      }
+      (l.result, r.result)
+    }
+
+    /** Iterates over the tails of this $coll. The first value will be this
+     *  $coll and the final one will be an empty $coll, with the intervening
+     *  values the results of successive applications of `tail`.
+     *
+     *  @return   an iterator over all the tails of this $coll
+     *  @example  `List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)`
+     */  
+    def tails: Iterator[Repr] = iterateUntilEmpty(_.tail)
+
+    /** Iterates over the inits of this $coll. The first value will be this
+     *  $coll and the final one will be an empty $coll, with the intervening
+     *  values the results of successive applications of `init`.
+     *
+     *  @return  an iterator over all the inits of this $coll
+     *  @example  `List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)`
+     */
+    def inits: Iterator[Repr] = iterateUntilEmpty(_.init)
+
+    /** Copies elements of this $coll to an array.
+     *  Fills the given array `xs` with at most `len` elements of
+     *  this $coll, starting at position `start`.
+     *  Copying will stop once either the end of the current $coll is reached,
+     *  or the end of the array is reached, or `len` elements have been copied.
+     *
+     *  $willNotTerminateInf
+     * 
+     *  @param  xs     the array to fill.
+     *  @param  start  the starting index.
+     *  @param  len    the maximal number of elements to copy.
+     *  @tparam B      the type of the elements of the array. 
+     * 
+     *
+     *  @usecase def copyToArray(xs: Array[A], start: Int, len: Int): Unit
+     */
+    def copyToArray[B >: A](xs: Array[B], start: Int, len: Int) {
+      var i = start
+      val end = (start + len) min xs.length
+      breakable {
+        for (x <- this) {
+          if (i >= end) break
+          xs(i) = x
+          i += 1
+        }
+      }
+    }
+
+    def toTraversable: Traversable[A] = thisCollection
+    def toIterator: Iterator[A] = toStream.iterator
+    def toStream: Stream[A] = toBuffer.toStream
+
+    /** Converts this $coll to a string.
+     *
+     *  @return   a string representation of this collection. By default this
+     *            string consists of the `stringPrefix` of this $coll,
+     *            followed by all elements separated by commas and enclosed in parentheses.
+     */
+    override def toString = mkString(stringPrefix + "(", ", ", ")")
+
+    /** Defines the prefix of this object's `toString` representation.
+     *
+     *  @return  a string representation which starts the result of `toString`
+     *           applied to this $coll. By default the string prefix is the
+     *           simple name of the collection class $coll.
+     */
+    def stringPrefix : String = {
+      var string = repr.asInstanceOf[AnyRef].getClass.getName
+      val idx1 = string.lastIndexOf('.' : Int)
+      if (idx1 != -1) string = string.substring(idx1 + 1)
+      val idx2 = string.indexOf('$')
+      if (idx2 != -1) string = string.substring(0, idx2)
+      string
+    }
+
+    /** Creates a non-strict view of this $coll.
+     * 
+     *  @return a non-strict view of this $coll.
+     */
+    def view = new TraversableView[A, Repr] {
+      protected lazy val underlying = self.repr
+      override def foreach[U](f: A => U) = self foreach f
+    }
+
+    /** Creates a non-strict view of a slice of this $coll.
+     *
+     *  Note: the difference between `view` and `slice` is that `view` produces
+     *        a view of the current $coll, whereas `slice` produces a new $coll.
+     * 
+     *  Note: `view(from, to)` is equivalent to `view.slice(from, to)`
+     *  $orderDependent
+     * 
+     *  @param from   the index of the first element of the view
+     *  @param until  the index of the element following the view
+     *  @return a non-strict view of a slice of this $coll, starting at index `from`
+     *  and extending up to (but not including) index `until`.
+     */
+    def view(from: Int, until: Int): TraversableView[A, Repr] = view.slice(from, until)
+
+    /** Creates a non-strict filter of this $coll.
+     *
+     *  Note: the difference between `c filter p` and `c withFilter p` is that
+     *        the former creates a new collection, whereas the latter only
+     *        restricts the domain of subsequent `map`, `flatMap`, `foreach`,
+     *        and `withFilter` operations.
+     *  $orderDependent
+     * 
+     *  @param p   the predicate used to test elements.
+     *  @return    an object of class `WithFilter`, which supports
+     *             `map`, `flatMap`, `foreach`, and `withFilter` operations.
+     *             All these operations apply to those elements of this $coll which
+     *             satisfy the predicate `p`.
+     */
+    def withFilter(p: A => Boolean): FilterMonadic[A, Repr] = new WithFilter(p)
+
+    /** A class supporting filtered operations. Instances of this class are
+     *  returned by method `withFilter`.
+     */
+    class WithFilter(p: A => Boolean) extends FilterMonadic[A, Repr] {
+
+      /** Builds a new collection by applying a function to all elements of the
+       *  outer $coll containing this `WithFilter` instance that satisfy predicate `p`.
+       *
+       *  @param f      the function to apply to each element.
+       *  @tparam B     the element type of the returned collection.
+       *  @tparam That  $thatinfo
+       *  @param bf     $bfinfo
+       *  @return       a new collection of type `That` resulting from applying
+       *                the given function `f` to each element of the outer $coll
+       *                that satisfies predicate `p` and collecting the results.
+       *
+       *  @usecase def map[B](f: A => B): $Coll[B] 
+       *  
+       *  @return       a new $coll resulting from applying the given function
+       *                `f` to each element of the outer $coll that satisfies
+       *                predicate `p` and collecting the results.
+       */
+      def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
+        val b = bf(repr)
+        for (x <- self) 
+          if (p(x)) b += f(x)
+        b.result
+      }
+
+      /** Builds a new collection by applying a function to all elements of the
+       *  outer $coll containing this `WithFilter` instance that satisfy
+       *  predicate `p` and concatenating the results. 
+       *
+       *  @param f      the function to apply to each element.
+       *  @tparam B     the element type of the returned collection.
+       *  @tparam That  $thatinfo
+       *  @param bf     $bfinfo
+       *  @return       a new collection of type `That` resulting from applying
+       *                the given collection-valued function `f` to each element
+       *                of the outer $coll that satisfies predicate `p` and
+       *                concatenating the results.
+       *
+       *  @usecase def flatMap[B](f: A => TraversableOnce[B]): $Coll[B]
+       * 
+       *  @return       a new $coll resulting from applying the given collection-valued function
+       *                `f` to each element of the outer $coll that satisfies predicate `p` and concatenating the results.
+       */
+      def flatMap[B, That](f: A => GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
+        val b = bf(repr)
+        for (x <- self) 
+          if (p(x)) b ++= f(x).seq
+        b.result
+      }
+
+      /** Applies a function `f` to all elements of the outer $coll containing
+       *  this `WithFilter` instance that satisfy predicate `p`.
+       *
+       *  @param  f   the function that is applied for its side-effect to every element.
+       *              The result of function `f` is discarded.
+       *              
+       *  @tparam  U  the type parameter describing the result of function `f`. 
+       *              This result will always be ignored. Typically `U` is `Unit`,
+       *              but this is not necessary.
+       *
+       *  @usecase def foreach(f: A => Unit): Unit
+       */   
+      def foreach[U](f: A => U): Unit = 
+        for (x <- self) 
+          if (p(x)) f(x)
+
+      /** Further refines the filter for this $coll.
+       *
+       *  @param q   the predicate used to test elements.
+       *  @return    an object of class `WithFilter`, which supports
+       *             `map`, `flatMap`, `foreach`, and `withFilter` operations.
+       *             All these operations apply to those elements of this $coll which
+       *             satisfy the predicate `q` in addition to the predicate `p`.
+       */
+      def withFilter(q: A => Boolean): WithFilter = 
+        new WithFilter(x => p(x) && q(x))
+    }
+
+    // A helper for tails and inits.
+    private def iterateUntilEmpty(f: Traversable[A @uV] => Traversable[A @uV]): Iterator[Repr] = {
+      val it = Iterator.iterate(thisCollection)(f) takeWhile (x => !x.isEmpty)
+      it ++ Iterator(Nil) map (newBuilder ++= _ result)
+    }
+  }
+
+
+

+ + + +