scala.collection.GenSeqLike

trait GenSeqLike[+A, +Repr] extends GenIterableLike[A, Repr] with Equals with Parallelizable[A, ParSeq[A]]

A template trait for all sequences which may be traversed in parallel.

• Source
  • GenSeqLike.scala - Blame
  • GenSeqLike.scala - History

Abstract Value Members From scala.Equals

abstract def canEqual(that: Any): Boolean

A method that should be called from every well-designed equals method that is open to be overridden in a subclass. See Programming in Scala, Chapter 28 for discussion and design.

• that
  • the value being probed for possible equality
• returns
  • true if this instance can possibly equal that , otherwise false
• Definition Classes
  • Equals

(defined at scala.Equals)

Concrete Value Members From scala.collection.GenIterableLike

abstract def sameElements[A1 >: A](that: GenIterable[A1]): Boolean

[use case]

Checks if the other iterable collection contains the same elements in the same order as this general sequence.

Note: might return different results for different runs, unless the underlying collection type is ordered.

Note: will not terminate for infinite-sized collections.

• that
  • the collection to compare with.
• returns
  • true , if both collections contain the same elements in the same order, false otherwise.
• Definition Classes
  • GenIterableLike

(defined at scala.collection.GenIterableLike)

abstract def zipAll[B, A1 >: A, That](that: GenIterable[B], thisElem: A1, thatElem: B)(implicit bf: CanBuildFrom[Repr, (A1, B), That]): That

[use case]

Returns a general sequence formed from this general sequence and another iterable collection by combining corresponding elements in pairs. If one of the two collections is shorter than the other, placeholder elements are used to extend the shorter collection to the length of the longer.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• B
  • the type of the second half of the returned pairs
• that
  • The iterable providing the second half of each result pair
• thisElem
  • the element to be used to fill up the result if this general sequence is shorter than that .
• thatElem
  • the element to be used to fill up the result if that is shorter than this general sequence.
• returns
  • a new general sequence containing pairs consisting of corresponding elements of this general sequence and that . The length of the returned collection is the maximum of the lengths of this general sequence and that . If this general sequence is shorter than that , thisElem values are used to pad the result. If that is shorter than this general sequence, thatElem values are used to pad the result.
• Definition Classes
  • GenIterableLike

(defined at scala.collection.GenIterableLike)

abstract def zipWithIndex[A1 >: A, That](implicit bf: CanBuildFrom[Repr, (A1, Int), That]): That

[use case]

Zips this general sequence with its indices.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• returns
  • A new general sequence containing pairs consisting of all elements of this general sequence paired with their index. Indices start at 0 .
• Definition Classes
  • GenIterableLike

Example:

List("a", "b", "c").zipWithIndex = List(("a", 0), ("b", 1), ("c", 2))

(defined at scala.collection.GenIterableLike)

abstract def zip[A1 >: A, B, That](that: GenIterable[B])(implicit bf: CanBuildFrom[Repr, (A1, B), That]): That

[use case]

Returns a general sequence formed from this general sequence and another iterable collection by combining corresponding elements in pairs. If one of the two collections is longer than the other, its remaining elements are ignored.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• B
  • the type of the second half of the returned pairs
• that
  • The iterable providing the second half of each result pair
• returns
  • a new general sequence containing pairs consisting of corresponding elements of this general sequence and that . The length of the returned collection is the minimum of the lengths of this general sequence and that .
• Definition Classes
  • GenIterableLike

(defined at scala.collection.GenIterableLike)

Abstract Value Members From scala.collection.GenSeqLike

abstract def apply(idx: Int): A

Selects an element by its index in the general sequence.

Example:

scala> val x = List(1, 2, 3, 4, 5)
x: List[Int] = List(1, 2, 3, 4, 5)

scala> x(3)
res1: Int = 4

• idx
  • The index to select.
• returns
  • the element of this general sequence at index idx , where 0 indicates the first element.
• Exceptions thrown
  • IndexOutOfBoundsException if idx does not satisfy 0 <= idx < length .

(defined at scala.collection.GenSeqLike)

abstract def corresponds[B](that: GenSeq[B])(p: (A, B) ⇒ Boolean): Boolean

Tests whether every element of this general sequence relates to the corresponding element of another sequence by satisfying a test predicate.

• B
  • the type of the elements of that
• that
  • the other sequence
• p
  • the test predicate, which relates elements from both sequences
• returns
  • true if both sequences have the same length and p(x, y) is true for all corresponding elements x of this general sequence and y of that , otherwise false .

(defined at scala.collection.GenSeqLike)

abstract def endsWith[B](that: GenSeq[B]): Boolean

Tests whether this general sequence ends with the given sequence.

Note: will not terminate for infinite-sized collections.

• that
  • the sequence to test
• returns
  • true if this general sequence has that as a suffix, false otherwise.

(defined at scala.collection.GenSeqLike)

abstract def indexWhere(p: (A) ⇒ Boolean, from: Int): Int

Finds index of the first element satisfying some predicate after or at some start index.

Note: may not terminate for infinite-sized collections.

• p
  • the predicate used to test elements.
• from
  • the start index
• returns
  • the index >= from of the first element of this general sequence that satisfies the predicate p , or -1 , if none exists.

(defined at scala.collection.GenSeqLike)

abstract def lastIndexWhere(p: (A) ⇒ Boolean, end: Int): Int

Finds index of last element satisfying some predicate before or at given end index.

• p
  • the predicate used to test elements.
• returns
  • the index <= end of the last element of this general sequence that satisfies the predicate p , or -1 , if none exists.

(defined at scala.collection.GenSeqLike)

abstract def segmentLength(p: (A) ⇒ Boolean, from: Int): Int

Computes length of longest segment whose elements all satisfy some predicate.

Note: may not terminate for infinite-sized collections.

• p
  • the predicate used to test elements.
• from
  • the index where the search starts.
• returns
  • the length of the longest segment of this general sequence starting from index from such that every element of the segment satisfies the predicate p .

(defined at scala.collection.GenSeqLike)

abstract def startsWith[B](that: GenSeq[B], offset: Int): Boolean

Tests whether this general sequence contains the given sequence at a given index.

Note : If the both the receiver object this and the argument that are infinite sequences this method may not terminate.

• that
  • the sequence to test
• offset
  • the index where the sequence is searched.
• returns
  • true if the sequence that is contained in this general sequence at index offset , otherwise false .

(defined at scala.collection.GenSeqLike)

abstract def toSeq: GenSeq[A]

Converts this general sequence to a sequence. As with toIterable , it’s lazy in this default implementation, as this TraversableOnce may be lazy and unevaluated.

Note: will not terminate for infinite-sized collections.

• returns
  • a sequence containing all elements of this general sequence.
• Definition Classes
  • GenSeqLike → GenTraversableOnce

(defined at scala.collection.GenSeqLike)

Concrete Value Members From scala.collection.GenSeqLike

abstract def distinct: Repr

Builds a new general sequence from this general sequence without any duplicate elements.

Note: will not terminate for infinite-sized collections.

• returns
  • A new general sequence which contains the first occurrence of every element of this general sequence.

(defined at scala.collection.GenSeqLike)

abstract def +:[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Repr, B, That]): That

[use case]

A copy of the general sequence with an element prepended.

Note that :-ending operators are right associative (see example). A mnemonic for +: vs. :+ is: the COLon goes on the COLlection side.

Also, the original general sequence is not modified, so you will want to capture the result.

Example:

scala> val x = List(1)
x: List[Int] = List(1)

scala> val y = 2 +: x
y: List[Int] = List(2, 1)

scala> println(x)
List(1)

• elem
  • the prepended element
• returns
  • a new general sequence consisting of elem followed by all elements of this general sequence.

(defined at scala.collection.GenSeqLike)

abstract def :+[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Repr, B, That]): That

[use case]

A copy of this general sequence with an element appended.

A mnemonic for +: vs. :+ is: the COLon goes on the COLlection side.

Note: will not terminate for infinite-sized collections.

Example:

scala> val a = List(1)
a: List[Int] = List(1)

scala> val b = a :+ 2
b: List[Int] = List(1, 2)

scala> println(a)
List(1)

• elem
  • the appended element
• returns
  • a new general sequence consisting of all elements of this general sequence followed by elem .

(defined at scala.collection.GenSeqLike)

abstract def diff[B >: A](that: GenSeq[B]): Repr

[use case]

Computes the multiset difference between this general sequence and another sequence.

Note: will not terminate for infinite-sized collections.

• that
  • the sequence of elements to remove
• returns
  • a new general sequence which contains all elements of this general sequence except some of occurrences of elements that also appear in that . If an element value x appears n times in that , then the first n occurrences of x will not form part of the result, but any following occurrences will.

(defined at scala.collection.GenSeqLike)

def equals(that: Any): Boolean

The equals method for arbitrary sequences. Compares this sequence to some other object.

• that
  • The object to compare the sequence to
• returns
  • true if that is a sequence that has the same elements as this sequence in the same order, false otherwise
• Definition Classes
  • GenSeqLike → Equals → Any

(defined at scala.collection.GenSeqLike)

def indexOf[B >: A](elem: B): Int

[use case]

Finds index of first occurrence of some value in this general sequence.

Note: may not terminate for infinite-sized collections.

• elem
  • the element value to search for.
• returns
  • the index of the first element of this general sequence that is equal (as determined by == ) to elem , or -1 , if none exists.

(defined at scala.collection.GenSeqLike)

def indexOf[B >: A](elem: B, from: Int): Int

[use case]

Finds index of first occurrence of some value in this general sequence after or at some start index.

Note: may not terminate for infinite-sized collections.

• elem
  • the element value to search for.
• from
  • the start index
• returns
  • the index >= from of the first element of this general sequence that is equal (as determined by == ) to elem , or -1 , if none exists.

(defined at scala.collection.GenSeqLike)

def indexWhere(p: (A) ⇒ Boolean): Int

Finds index of first element satisfying some predicate.

Note: may not terminate for infinite-sized collections.

• p
  • the predicate used to test elements.
• returns
  • the index of the first element of this general sequence that satisfies the predicate p , or -1 , if none exists.

(defined at scala.collection.GenSeqLike)

abstract def intersect[B >: A](that: GenSeq[B]): Repr

[use case]

Computes the multiset intersection between this general sequence and another sequence.

Note: may not terminate for infinite-sized collections.

• that
  • the sequence of elements to intersect with.
• returns
  • a new general sequence which contains all elements of this general sequence which also appear in that . If an element value x appears n times in that , then the first n occurrences of x will be retained in the result, but any following occurrences will be omitted.

(defined at scala.collection.GenSeqLike)

def isDefinedAt(idx: Int): Boolean

Tests whether this general sequence contains given index.

The implementations of methods apply and isDefinedAt turn a Seq[A] into a PartialFunction[Int, A] .

• idx
  • the index to test
• returns
  • true if this general sequence contains an element at position idx , false otherwise.

(defined at scala.collection.GenSeqLike)

def lastIndexOf[B >: A](elem: B): Int

[use case]

Finds index of last occurrence of some value in this general sequence.

Note: will not terminate for infinite-sized collections.

• elem
  • the element value to search for.
• returns
  • the index of the last element of this general sequence that is equal (as determined by == ) to elem , or -1 , if none exists.

(defined at scala.collection.GenSeqLike)

def lastIndexOf[B >: A](elem: B, end: Int): Int

[use case]

Finds index of last occurrence of some value in this general sequence before or at a given end index.

• elem
  • the element value to search for.
• end
  • the end index.
• returns
  • the index <= end of the last element of this general sequence that is equal (as determined by == ) to elem , or -1 , if none exists.

(defined at scala.collection.GenSeqLike)

def lastIndexWhere(p: (A) ⇒ Boolean): Int

Finds index of last element satisfying some predicate.

Note: will not terminate for infinite-sized collections.

• p
  • the predicate used to test elements.
• returns
  • the index of the last element of this general sequence that satisfies the predicate p , or -1 , if none exists.

(defined at scala.collection.GenSeqLike)

abstract def padTo[B >: A, That](len: Int, elem: B)(implicit bf: CanBuildFrom[Repr, B, That]): That

[use case]

A copy of this general sequence with an element value appended until a given target length is reached.

• len
  • the target length
• elem
  • the padding value
• returns
  • a new general sequence consisting of all elements of this general sequence followed by the minimal number of occurrences of elem so that the resulting general sequence has a length of at least len .

(defined at scala.collection.GenSeqLike)

abstract def patch[B >: A, That](from: Int, patch: GenSeq[B], replaced: Int)(implicit bf: CanBuildFrom[Repr, B, That]): That

[use case]

Produces a new general sequence where a slice of elements in this general sequence is replaced by another sequence.

• from
  • the index of the first replaced element
• replaced
  • the number of elements to drop in the original general sequence
• returns
  • a new general sequence consisting of all elements of this general sequence except that replaced elements starting from from are replaced by patch .

(defined at scala.collection.GenSeqLike)

def prefixLength(p: (A) ⇒ Boolean): Int

Returns the length of the longest prefix whose elements all satisfy some predicate.

Note: may not terminate for infinite-sized collections.

• p
  • the predicate used to test elements.
• returns
  • the length of the longest prefix of this general sequence such that every element of the segment satisfies the predicate p .

(defined at scala.collection.GenSeqLike)

abstract def reverseMap[B, That](f: (A) ⇒ B)(implicit bf: CanBuildFrom[Repr, B, That]): That

[use case]

Builds a new collection by applying a function to all elements of this general sequence and collecting the results in reversed order.

Note: will not terminate for infinite-sized collections.

Note: xs.reverseMap(f) is the same as xs.reverse.map(f) but might be more efficient.

• B
  • the element type of the returned collection.
• f
  • the function to apply to each element.
• returns
  • a new general sequence resulting from applying the given function f to each element of this general sequence and collecting the results in reversed order.

(defined at scala.collection.GenSeqLike)

def startsWith[B](that: GenSeq[B]): Boolean

Tests whether this general sequence starts with the given sequence.

• that
  • the sequence to test
• returns
  • true if this collection has that as a prefix, false otherwise.

(defined at scala.collection.GenSeqLike)

def union[B >: A, That](that: GenSeq[B])(implicit bf: CanBuildFrom[Repr, B, That]): That

[use case]

Produces a new sequence which contains all elements of this general sequence and also all elements of a given sequence. xs union ys is equivalent to xs ++ ys .

Another way to express this is that xs union ys computes the order-preserving multi-set union of xs and ys . union is hence a counter-part of diff and intersect which also work on multi-sets.

Note: will not terminate for infinite-sized collections.

• that
  • the sequence to add.
• returns
  • a new general sequence which contains all elements of this general sequence followed by all elements of that .

(defined at scala.collection.GenSeqLike)

abstract def updated[B >: A, That](index: Int, elem: B)(implicit bf: CanBuildFrom[Repr, B, That]): That

[use case]

A copy of this general sequence with one single replaced element.

• index
  • the position of the replacement
• elem
  • the replacing element
• returns
  • a copy of this general sequence with the element at position index replaced by elem .

(defined at scala.collection.GenSeqLike)

Abstract Value Members From scala.collection.GenTraversableLike

abstract def drop(n: Int): Repr

Selects all elements except first n ones.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• n
  • the number of elements to drop from this general collection.
• returns
  • a general collection consisting of all elements of this general collection except the first n ones, or else the empty general collection, if this general collection has less than n elements.
• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

abstract def dropWhile(pred: (A) ⇒ Boolean): Repr

Drops longest prefix of elements that satisfy a predicate.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• pred
  • The predicate used to test elements.
• returns
  • the longest suffix of this general collection whose first element does not satisfy the predicate p .
• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

abstract def filter(pred: (A) ⇒ Boolean): Repr

Selects all elements of this general collection which satisfy a predicate.

• pred
  • the predicate used to test elements.
• returns
  • a new general collection consisting of all elements of this general collection that satisfy the given predicate p . Their order may not be preserved.
• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

abstract def filterNot(pred: (A) ⇒ Boolean): Repr

Selects all elements of this general collection which do not satisfy a predicate.

• pred
  • the predicate used to test elements.
• returns
  • a new general collection consisting of all elements of this general collection that do not satisfy the given predicate p . Their order may not be preserved.
• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

abstract def groupBy[K](f: (A) ⇒ K): GenMap[K, Repr]

Partitions this general collection into a map of general collections according to some discriminator function.

Note: this method is not re-implemented by views. This means when applied to a view it will always force the view and return a new general collection.

• K
  • the type of keys returned by the discriminator function.
• f
  • the discriminator function.
• returns
  • A map from keys to general collections such that the following invariant holds:

    (xs groupBy f)(k) = xs filter (x => f(x) == k)
    

That is, every key `k` is bound to a general collection of those elements
 `x` for which `f(x)` equals `k` .

• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

abstract def partition(pred: (A) ⇒ Boolean): (Repr, Repr)

Partitions this general collection in two general collections according to a predicate.

• pred
  • the predicate on which to partition.
• returns
  • a pair of general collections: the first general collection consists of all elements that satisfy the predicate p and the second general collection consists of all elements that don’t. The relative order of the elements in the resulting general collections may not be preserved.
• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

abstract def scanLeft[B, That](z: B)(op: (B, A) ⇒ B)(implicit bf: CanBuildFrom[Repr, B, That]): That

Produces a collection containing cumulative results of applying the operator going left to right.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• B
  • the type of the elements in the resulting collection
• That
  • the actual type of the resulting collection
• z
  • the initial value
• op
  • the binary operator applied to the intermediate result and the element
• bf
  • an implicit value of class CanBuildFrom which determines the result class That from the current representation type Repr and and the new element type B .
• returns
  • collection with intermediate results
• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

abstract def scanRight[B, That](z: B)(op: (A, B) ⇒ B)(implicit bf: CanBuildFrom[Repr, B, That]): That

Produces a collection containing cumulative results of applying the operator going right to left. The head of the collection is the last cumulative result.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered.

Example:

List(1, 2, 3, 4).scanRight(0)(_ + _) == List(10, 9, 7, 4, 0)

• B
  • the type of the elements in the resulting collection
• That
  • the actual type of the resulting collection
• z
  • the initial value
• op
  • the binary operator applied to the intermediate result and the element
• bf
  • an implicit value of class CanBuildFrom which determines the result class That from the current representation type Repr and and the new element type B .
• returns
  • collection with intermediate results
• Definition Classes
  • GenTraversableLike
• Annotations
  • @migration
• Migration
  • (Changed in version 2.9.0) The behavior of scanRight has changed. The previous behavior can be reproduced with scanRight.reverse.

(defined at scala.collection.GenTraversableLike)

abstract def scan[B >: A, That](z: B)(op: (B, B) ⇒ B)(implicit cbf: CanBuildFrom[Repr, B, That]): That

Computes a prefix scan of the elements of the collection.

Note: The neutral element z may be applied more than once.

• B
  • element type of the resulting collection
• That
  • type of the resulting collection
• z
  • neutral element for the operator op
• op
  • the associative operator for the scan
• cbf
  • combiner factory which provides a combiner
• returns
  • a new general collection containing the prefix scan of the elements in this general collection
• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

abstract def slice(unc_from: Int, unc_until: Int): Repr

Selects an interval of elements. The returned collection is made up of all elements x which satisfy the invariant:

from <= indexOf(x) < until

Note: might return different results for different runs, unless the underlying collection type is ordered.

• unc_from
  • the lowest index to include from this general collection.
• unc_until
  • the lowest index to EXCLUDE from this general collection.
• returns
  • a general collection containing the elements greater than or equal to index from extending up to (but not including) index until of this general collection.
• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

abstract def span(pred: (A) ⇒ Boolean): (Repr, Repr)

Splits this general collection into a prefix/suffix pair according to a predicate.

Note: c span p is equivalent to (but possibly more efficient than) (c takeWhile p, c dropWhile p) , provided the evaluation of the predicate p does not cause any side-effects.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• pred
  • the test predicate
• returns
  • a pair consisting of the longest prefix of this general collection whose elements all satisfy p , and the rest of this general collection.
• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

abstract def splitAt(n: Int): (Repr, Repr)

Splits this general collection into two at a given position. Note: c splitAt n is equivalent to (but possibly more efficient than) (c take n, c drop n) .

Note: might return different results for different runs, unless the underlying collection type is ordered.

• n
  • the position at which to split.
• returns
  • a pair of general collections consisting of the first n elements of this general collection, and the other elements.
• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

abstract def take(n: Int): Repr

Selects first n elements.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• n
  • the number of elements to take from this general collection.
• returns
  • a general collection consisting only of the first n elements of this general collection, or else the whole general collection, if it has less than n elements.
• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

abstract def takeWhile(pred: (A) ⇒ Boolean): Repr

Takes longest prefix of elements that satisfy a predicate.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• pred
  • The predicate used to test elements.
• returns
  • the longest prefix of this general collection whose elements all satisfy the predicate p .
• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

Concrete Value Members From scala.collection.GenTraversableLike

abstract def ++[B >: A, That](that: GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That

[use case]

Returns a new general sequence containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the general sequence is the most specific superclass encompassing the element types of the two operands.

Example:

scala> val a = List(1)
a: List[Int] = List(1)

scala> val b = List(2)
b: List[Int] = List(2)

scala> val c = a ++ b
c: List[Int] = List(1, 2)

scala> val d = List('a')
d: List[Char] = List(a)

scala> val e = c ++ d
e: List[AnyVal] = List(1, 2, a)

• B
  • the element type of the returned collection.
• that
  • the traversable to append.
• returns
  • a new general sequence which contains all elements of this general sequence followed by all elements of that .
• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

abstract def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Repr, B, That]): That

[use case]

Builds a new collection by applying a partial function to all elements of this general sequence on which the function is defined.

• B
  • the element type of the returned collection.
• pf
  • the partial function which filters and maps the general sequence.
• returns
  • a new general sequence resulting from applying the given partial function pf to each element on which it is defined and collecting the results. The order of the elements is preserved.
• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

abstract def flatMap[B, That](f: (A) ⇒ GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That

[use case]

Builds a new collection by applying a function to all elements of this general sequence and using the elements of the resulting collections.

For example:

def getWords(lines: Seq[String]): Seq[String] = lines flatMap (line => line split "\\W+")

The type of the resulting collection is guided by the static type of general sequence. This might cause unexpected results sometimes. For example:

// lettersOf will return a Seq[Char] of likely repeated letters, instead of a Set
def lettersOf(words: Seq[String]) = words flatMap (word => word.toSet)

// lettersOf will return a Set[Char], not a Seq
def lettersOf(words: Seq[String]) = words.toSet flatMap (word => word.toSeq)

// xs will be an Iterable[Int]
val xs = Map("a" -> List(11,111), "b" -> List(22,222)).flatMap(_._2)

// ys will be a Map[Int, Int]
val ys = Map("a" -> List(1 -> 11,1 -> 111), "b" -> List(2 -> 22,2 -> 222)).flatMap(_._2)

• B
  • the element type of the returned collection.
• f
  • the function to apply to each element.
• returns
  • a new general sequence resulting from applying the given collection-valued function f to each element of this general sequence and concatenating the results.
• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

abstract def foreach[U](f: (A) ⇒ U): Unit

[use case]

Applies a function f to all elements of this general sequence.

Note: this method underlies the implementation of most other bulk operations. It’s important to implement this method in an efficient way.

• f
  • the function that is applied for its side-effect to every element. The result of function f is discarded.
• Definition Classes
  • GenTraversableLike → GenTraversableOnce

(defined at scala.collection.GenTraversableLike)

abstract def map[B, That](f: (A) ⇒ B)(implicit bf: CanBuildFrom[Repr, B, That]): That

[use case]

Builds a new collection by applying a function to all elements of this general sequence.

• B
  • the element type of the returned collection.
• f
  • the function to apply to each element.
• returns
  • a new general sequence resulting from applying the given function f to each element of this general sequence and collecting the results.
• Definition Classes
  • GenTraversableLike

(defined at scala.collection.GenTraversableLike)

Abstract Value Members From scala.collection.GenTraversableOnce

abstract def /:[B](z: B)(op: (B, A) ⇒ B): B

Applies a binary operator to a start value and all elements of this collection or iterator, going left to right.

Note: /: is alternate syntax for foldLeft ; z /: xs is the same as xs foldLeft z .

Examples:

Note that the folding function used to compute b is equivalent to that used to compute c.

scala> val a = List(1,2,3,4)
a: List[Int] = List(1, 2, 3, 4)

scala> val b = (5 /: a)(_+_)
b: Int = 15

scala> val c = (5 /: a)((x,y) => x + y)
c: Int = 15

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.

• B
  • the result type of the binary operator.
• z
  • the start value.
• op
  • the binary operator.
• returns
  • the result of inserting op between consecutive elements of this collection or iterator, going left to right with the start value z on the left:

    op(...op(op(z, x_1), x_2), ..., x_n)
    

where `x1, ..., xn` are the elements of this collection or iterator.

• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def :\[B](z: B)(op: (A, B) ⇒ B): B

Applies a binary operator to all elements of this collection or iterator and a start value, going right to left.

Note: :\ is alternate syntax for foldRight ; xs :\ z is the same as xs foldRight z .

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.

Examples:

Note that the folding function used to compute b is equivalent to that used to compute c.

scala> val a = List(1,2,3,4)
a: List[Int] = List(1, 2, 3, 4)

scala> val b = (a :\ 5)(_+_)
b: Int = 15

scala> val c = (a :\ 5)((x,y) => x + y)
c: Int = 15

• B
  • the result type of the binary operator.
• z
  • the start value
• op
  • the binary operator
• returns
  • the result of inserting op between consecutive elements of this collection or iterator, going right to left with the start value z on the right:

    op(x_1, op(x_2, ... op(x_n, z)...))
    

where `x1, ..., xn` are the elements of this collection or iterator.

• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def aggregate[B](z: ⇒ B)(seqop: (B, A) ⇒ B, combop: (B, B) ⇒ B): B

Aggregates the results of applying an operator to subsequent elements.

This is a more general form of fold and reduce . It is similar to foldLeft in that it doesn’t require the result to be a supertype of the element type. In addition, it allows parallel collections to be processed in chunks, and then combines the intermediate results.

aggregate splits the collection or iterator into partitions and processes each partition by sequentially applying seqop , starting with z (like foldLeft ). Those intermediate results are then combined by using combop (like fold ). The implementation of this operation may operate on an arbitrary number of collection partitions (even 1), so combop may be invoked an arbitrary number of times (even 0).

As an example, consider summing up the integer values of a list of chars. The initial value for the sum is 0. First, seqop transforms each input character to an Int and adds it to the sum (of the partition). Then, combop just needs to sum up the intermediate results of the partitions:

List('a', 'b', 'c').aggregate(0)({ (sum, ch) => sum + ch.toInt }, { (p1, p2) => p1 + p2 })

• B
  • the type of accumulated results
• z
  • the initial value for the accumulated result of the partition - this will typically be the neutral element for the seqop operator (e.g. Nil for list concatenation or 0 for summation) and may be evaluated more than once
• seqop
  • an operator used to accumulate results within a partition
• combop
  • an associative operator used to combine results from different partitions
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def count(p: (A) ⇒ Boolean): Int

Counts the number of elements in the collection or iterator which satisfy a predicate.

• p
  • the predicate used to test elements.
• returns
  • the number of elements satisfying the predicate p .
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def exists(p: (A) ⇒ Boolean): Boolean

Tests whether a predicate holds for at least one element of this collection or iterator.

Note: may not terminate for infinite-sized collections.

• p
  • the predicate used to test elements.
• returns
  • true if the given predicate p is satisfied by at least one element of this collection or iterator, otherwise false
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def find(p: (A) ⇒ Boolean): Option[A]

Finds the first element of the collection or iterator satisfying a predicate, if any.

Note: may not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• p
  • the predicate used to test elements.
• returns
  • an option value containing the first element in the collection or iterator that satisfies p , or None if none exists.
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def foldLeft[B](z: B)(op: (B, A) ⇒ B): B

Applies a binary operator to a start value and all elements of this collection or iterator, going left to right.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.

• B
  • the result type of the binary operator.
• z
  • the start value.
• op
  • the binary operator.
• returns
  • the result of inserting op between consecutive elements of this collection or iterator, going left to right with the start value z on the left:

    op(...op(z, x_1), x_2, ..., x_n)
    

where `x1, ..., xn` are the elements of this collection or iterator. Returns
 `z` if this collection or iterator is empty.

• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def foldRight[B](z: B)(op: (A, B) ⇒ B): B

Applies a binary operator to all elements of this collection or iterator and a start value, going right to left.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.

• B
  • the result type of the binary operator.
• z
  • the start value.
• op
  • the binary operator.
• returns
  • the result of inserting op between consecutive elements of this collection or iterator, going right to left with the start value z on the right:

    op(x_1, op(x_2, ... op(x_n, z)...))
    

where `x1, ..., xn` are the elements of this collection or iterator. Returns
 `z` if this collection or iterator is empty.

• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def fold[A1 >: A](z: A1)(op: (A1, A1) ⇒ A1): A1

Folds the elements of this collection or iterator using the specified associative binary operator.

The order in which operations are performed on elements is unspecified and may be nondeterministic.

Note: will not terminate for infinite-sized collections.

• A1
  • a type parameter for the binary operator, a supertype of A .
• z
  • a neutral element for the fold operation; may be added to the result an arbitrary number of times, and must not change the result (e.g., Nil for list concatenation, 0 for addition, or 1 for multiplication).
• op
  • a binary operator that must be associative.
• returns
  • the result of applying the fold operator op between all the elements and z , or z if this collection or iterator is empty.
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def forall(p: (A) ⇒ Boolean): Boolean

Tests whether a predicate holds for all elements of this collection or iterator.

Note: may not terminate for infinite-sized collections.

• p
  • the predicate used to test elements.
• returns
  • true if this collection or iterator is empty or the given predicate p holds for all elements of this collection or iterator, otherwise false .
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def mkString(sep: String): String

Displays all elements of this collection or iterator in a string using a separator string.

• sep
  • the separator string.
• returns
  • a string representation of this collection or iterator. In the resulting string the string representations (w.r.t. the method toString ) of all elements of this collection or iterator are separated by the string sep .
• Definition Classes
  • GenTraversableOnce

Example:

List(1, 2, 3).mkString("|") = "1|2|3"

(defined at scala.collection.GenTraversableOnce)

abstract def mkString(start: String, sep: String, end: String): String

Displays all elements of this collection or iterator in a string using start, end, and separator strings.

• start
  • the starting string.
• sep
  • the separator string.
• end
  • the ending string.
• returns
  • a string representation of this collection or iterator. The resulting string begins with the string start and ends with the string end . Inside, the string representations (w.r.t. the method toString ) of all elements of this collection or iterator are separated by the string sep .
• Definition Classes
  • GenTraversableOnce

Example:

List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"

(defined at scala.collection.GenTraversableOnce)

abstract def reduceLeftOption[B >: A](op: (B, A) ⇒ B): Option[B]

Optionally applies a binary operator to all elements of this collection or iterator, going left to right.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.

• B
  • the result type of the binary operator.
• op
  • the binary operator.
• returns
  • an option value containing the result of reduceLeft(op) if this collection or iterator is nonempty, None otherwise.
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def reduceOption[A1 >: A](op: (A1, A1) ⇒ A1): Option[A1]

Reduces the elements of this collection or iterator, if any, using the specified associative binary operator.

The order in which operations are performed on elements is unspecified and may be nondeterministic.

• A1
  • A type parameter for the binary operator, a supertype of A .
• op
  • A binary operator that must be associative.
• returns
  • An option value containing result of applying reduce operator op between all the elements if the collection is nonempty, and None otherwise.
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def reduceRightOption[B >: A](op: (A, B) ⇒ B): Option[B]

Optionally applies a binary operator to all elements of this collection or iterator, going right to left.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.

• B
  • the result type of the binary operator.
• op
  • the binary operator.
• returns
  • an option value containing the result of reduceRight(op) if this collection or iterator is nonempty, None otherwise.
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def reduceRight[B >: A](op: (A, B) ⇒ B): B

Applies a binary operator to all elements of this collection or iterator, going right to left.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.

• B
  • the result type of the binary operator.
• op
  • the binary operator.
• returns
  • the result of inserting op between consecutive elements of this collection or iterator, going right to left:

    op(x_1, op(x_2, ..., op(x_{n-1}, x_n)...))
    

where `x1, ..., xn` are the elements of this collection or iterator.

• Definition Classes
  • GenTraversableOnce
• Exceptions thrown
  • UnsupportedOperationException if this collection or iterator is empty.

(defined at scala.collection.GenTraversableOnce)

abstract def reduce[A1 >: A](op: (A1, A1) ⇒ A1): A1

Reduces the elements of this collection or iterator using the specified associative binary operator.

The order in which operations are performed on elements is unspecified and may be nondeterministic.

• A1
  • A type parameter for the binary operator, a supertype of A .
• op
  • A binary operator that must be associative.
• returns
  • The result of applying reduce operator op between all the elements if the collection or iterator is nonempty.
• Definition Classes
  • GenTraversableOnce
• Exceptions thrown
  • UnsupportedOperationException if this collection or iterator is empty.

(defined at scala.collection.GenTraversableOnce)

abstract def toBuffer[A1 >: A]: Buffer[A1]

Uses the contents of this collection or iterator to create a new mutable buffer.

Note: will not terminate for infinite-sized collections.

• returns
  • a buffer containing all elements of this collection or iterator.
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def toIndexedSeq: immutable.IndexedSeq[A]

Converts this collection or iterator to an indexed sequence.

Note: will not terminate for infinite-sized collections.

• returns
  • an indexed sequence containing all elements of this collection or iterator.
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def toIterable: GenIterable[A]

Converts this collection or iterator to an iterable collection. Note that the choice of target Iterable is lazy in this default implementation as this TraversableOnce may be lazy and unevaluated (i.e. it may be an iterator which is only traversable once).

Note: will not terminate for infinite-sized collections.

• returns
  • an Iterable containing all elements of this collection or iterator.
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def toSet[A1 >: A]: GenSet[A1]

Converts this collection or iterator to a set.

Note: will not terminate for infinite-sized collections.

• returns
  • a set containing all elements of this collection or iterator.
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def toTraversable: GenTraversable[A]

Converts this collection or iterator to an unspecified Traversable. Will return the same collection if this instance is already Traversable.

Note: will not terminate for infinite-sized collections.

• returns
  • a Traversable containing all elements of this collection or iterator.
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

Concrete Value Members From scala.collection.GenTraversableOnce

abstract def copyToArray[B >: A](xs: Array[B]): Unit

[use case]

Copies the elements of this general sequence to an array. Fills the given array xs with values of this general sequence. Copying will stop once either the end of the current general sequence is reached, or the end of the target array is reached.

Note: will not terminate for infinite-sized collections.

• xs
  • the array to fill.
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def copyToArray[B >: A](xs: Array[B], start: Int): Unit

[use case]

Copies the elements of this general sequence to an array. Fills the given array xs with values of this general sequence, beginning at index start . Copying will stop once either the end of the current general sequence is reached, or the end of the target array is reached.

Note: will not terminate for infinite-sized collections.

• xs
  • the array to fill.
• start
  • the starting index.
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def copyToArray[B >: A](xs: Array[B], start: Int, len: Int): Unit

[use case]

Copies the elements of this general sequence to an array. Fills the given array xs with at most len elements of this general sequence, starting at position start . Copying will stop once either the end of the current general sequence is reached, or the end of the target array is reached, or len elements have been copied.

Note: will not terminate for infinite-sized collections.

• xs
  • the array to fill.
• start
  • the starting index.
• len
  • the maximal number of elements to copy.
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def maxBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A

[use case]

Finds the first element which yields the largest value measured by function f.

• B
  • The result type of the function f.
• f
  • The measuring function.
• returns
  • the first element of this general sequence with the largest value measured by function f.
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def minBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A

[use case]

Finds the first element which yields the smallest value measured by function f.

• B
  • The result type of the function f.
• f
  • The measuring function.
• returns
  • the first element of this general sequence with the smallest value measured by function f.
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

abstract def toMap[K, V](implicit ev: <:<[A, (K, V)]): GenMap[K, V]

[use case]

Converts this general sequence to a map. This method is unavailable unless the elements are members of Tuple2, each ((T, U)) becoming a key-value pair in the map. Duplicate keys will be overwritten by later keys: if this is an unordered collection, which key is in the resulting map is undefined.

Note: will not terminate for infinite-sized collections.

• returns
  • a map of type immutable.Map[T, U] containing all key/value pairs of type (T, U) of this general sequence.
• Definition Classes
  • GenTraversableOnce

(defined at scala.collection.GenTraversableOnce)

Abstract Value Members From scala.collection.Parallelizable

abstract def parCombiner: Combiner[A, ParSeq[A]]

The default par implementation uses the combiner provided by this method to create a new parallel collection.

• returns
  • a combiner for the parallel collection of type ParRepr
• Attributes
  • protected[this]
• Definition Classes
  • Parallelizable

(defined at scala.collection.Parallelizable)

Concrete Value Members From scala.collection.Parallelizable

def par: ParSeq[A]

Returns a parallel implementation of this collection.

For most collection types, this method creates a new parallel collection by copying all the elements. For these collection, par takes linear time. Mutable collections in this category do not produce a mutable parallel collection that has the same underlying dataset, so changes in one collection will not be reflected in the other one.

Specific collections (e.g. ParArray or mutable.ParHashMap ) override this default behaviour by creating a parallel collection which shares the same underlying dataset. For these collections, par takes constant or sublinear time.

All parallel collections return a reference to themselves.

• returns
  • a parallel implementation of this collection
• Definition Classes
  • Parallelizable

(defined at scala.collection.Parallelizable)

Concrete Value Members From Implicit scala.collection.parallel.CollectionsHaveToParArray ——————————————————————————–

def toParArray: ParArray[T]

• Implicit information
  • This member is added by an implicit conversion from GenSeqLike [A, Repr] to CollectionsHaveToParArray [GenSeqLike [A, Repr], T] performed by method CollectionsHaveToParArray in scala.collection.parallel. This conversion will take place only if an implicit value of type (GenSeqLike [A, Repr]) ⇒ GenTraversableOnce [T] is in scope.
• Definition Classes
  • CollectionsHaveToParArray (added by implicit convertion: scala.collection.parallel.CollectionsHaveToParArray)

Full Source:

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala
package collection

import generic._

/** A template trait for all sequences which may be traversed
 *  in parallel.
 *
 *  @define Coll GenSeq
 *  @define coll general sequence
 *  @define mayNotTerminateInf
 *
 *    Note: may not terminate for infinite-sized collections.
 *  @define willNotTerminateInf
 *
 *    Note: will not terminate for infinite-sized collections.
 *
 *  @author Martin Odersky
 *  @author Aleksandar Prokopec
 *  @since 2.9
 *  @define seqInfo
 *  Sequences are special cases of iterable collections of class `Iterable`.
 *  Unlike iterables, sequences always have a defined order of elements.
 */
trait GenSeqLike[+A, +Repr] extends Any with GenIterableLike[A, Repr] with Equals with Parallelizable[A, parallel.ParSeq[A]] {
  def seq: Seq[A]

  /** Selects an element by its index in the $coll.
   *
   * Example:
   *
   * {{{
   *    scala> val x = List(1, 2, 3, 4, 5)
   *    x: List[Int] = List(1, 2, 3, 4, 5)
   *
   *    scala> x(3)
   *    res1: Int = 4
   * }}}
   *
   *  @param  idx  The index to select.
   *  @return the element of this $coll at index `idx`, where `0` indicates the first element.
   *  @throws IndexOutOfBoundsException if `idx` does not satisfy `0 <= idx < length`.
   */
  def apply(idx: Int): A

  /** The length of the $coll.
   *
   *  $willNotTerminateInf
   *
   *  Note: `xs.length` and `xs.size` yield the same result.
   *
   *  @return     the number of elements in this $coll.
   */
  def length: Int

  /** Tests whether this $coll contains given index.
   *
   *  The implementations of methods `apply` and `isDefinedAt` turn a `Seq[A]` into
   *  a `PartialFunction[Int, A]`.
   *
   * @param    idx     the index to test
   * @return   `true` if this $coll contains an element at position `idx`, `false` otherwise.
   */
  def isDefinedAt(idx: Int): Boolean = (idx >= 0) && (idx < length)

  /** Computes length of longest segment whose elements all satisfy some predicate.
   *
   *  $mayNotTerminateInf
   *
   *  @param   p     the predicate used to test elements.
   *  @param   from  the index where the search starts.
   *  @return  the length of the longest segment of this $coll starting from index `from`
   *           such that every element of the segment satisfies the predicate `p`.
   */
  def segmentLength(p: A => Boolean, from: Int): Int

  /** Returns the length of the longest prefix whose elements all satisfy some predicate.
   *
   *  $mayNotTerminateInf
   *
   *  @param   p     the predicate used to test elements.
   *  @return  the length of the longest prefix of this $coll
   *           such that every element of the segment satisfies the predicate `p`.
   */
  def prefixLength(p: A => Boolean): Int = segmentLength(p, 0)

  /** Finds index of the first element satisfying some predicate after or at some start index.
   *
   *  $mayNotTerminateInf
   *
   *  @param   p     the predicate used to test elements.
   *  @param   from   the start index
   *  @return  the index `>= from` of the first element of this $coll that satisfies the predicate `p`,
   *           or `-1`, if none exists.
   */
  def indexWhere(p: A => Boolean, from: Int): Int

  /** Finds index of first element satisfying some predicate.
   *
   *  $mayNotTerminateInf
   *
   *  @param   p     the predicate used to test elements.
   *  @return  the index of the first element of this $coll that satisfies the predicate `p`,
   *           or `-1`, if none exists.
   */
  def indexWhere(p: A => Boolean): Int = indexWhere(p, 0)

  /** Finds index of first occurrence of some value in this $coll.
   *
   *  @param   elem   the element value to search for.
   *  @tparam  B      the type of the element `elem`.
   *  @return  the index of the first element of this $coll that is equal (as determined by `==`)
   *           to `elem`, or `-1`, if none exists.
   *
   *  @usecase def indexOf(elem: A): Int
   *    @inheritdoc
   *
   *    $mayNotTerminateInf
   *
   */
  def indexOf[B >: A](elem: B): Int = indexOf(elem, 0)

  /** Finds index of first occurrence of some value in this $coll after or at some start index.
   *
   *  @param   elem   the element value to search for.
   *  @tparam  B      the type of the element `elem`.
   *  @param   from   the start index
   *  @return  the index `>= from` of the first element of this $coll that is equal (as determined by `==`)
   *           to `elem`, or `-1`, if none exists.
   *
   *  @usecase def indexOf(elem: A, from: Int): Int
   *    @inheritdoc
   *
   *    $mayNotTerminateInf
   *
   */
  def indexOf[B >: A](elem: B, from: Int): Int = indexWhere(elem == _, from)

  /** Finds index of last occurrence of some value in this $coll.
   *
   *  @param   elem   the element value to search for.
   *  @tparam  B      the type of the element `elem`.
   *  @return  the index of the last element of this $coll that is equal (as determined by `==`)
   *           to `elem`, or `-1`, if none exists.
   *
   *  @usecase def lastIndexOf(elem: A): Int
   *    @inheritdoc
   *
   *    $willNotTerminateInf
   *
   */
  def lastIndexOf[B >: A](elem: B): Int = lastIndexWhere(elem == _)

  /** Finds index of last occurrence of some value in this $coll before or at a given end index.
   *
   *  @param   elem   the element value to search for.
   *  @param   end    the end index.
   *  @tparam  B      the type of the element `elem`.
   *  @return  the index `<= end` of the last element of this $coll that is equal (as determined by `==`)
   *           to `elem`, or `-1`, if none exists.
   *
   *  @usecase def lastIndexOf(elem: A, end: Int): Int
   *    @inheritdoc
   */
  def lastIndexOf[B >: A](elem: B, end: Int): Int = lastIndexWhere(elem == _, end)

  /** Finds index of last element satisfying some predicate.
   *
   *  $willNotTerminateInf
   *
   *  @param   p     the predicate used to test elements.
   *  @return  the index of the last element of this $coll that satisfies the predicate `p`,
   *           or `-1`, if none exists.
   */
  def lastIndexWhere(p: A => Boolean): Int = lastIndexWhere(p, length - 1)

  /** Finds index of last element satisfying some predicate before or at given end index.
   *
   *  @param   p     the predicate used to test elements.
   *  @return  the index `<= end` of the last element of this $coll that satisfies the predicate `p`,
   *           or `-1`, if none exists.
   */
  def lastIndexWhere(p: A => Boolean, end: Int): Int

  /** Returns new $coll with elements in reversed order.
   *
   *  $willNotTerminateInf
   *
   *  @return A new $coll with all elements of this $coll in reversed order.
   */
  def reverse: Repr

  /**
   *  Builds a new collection by applying a function to all elements of this $coll and
   *  collecting the results in reversed order.
   *
   *  @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 this $coll and collecting the results in reversed order.
   *
   *  @usecase def reverseMap[B](f: A => B): $Coll[B]
   *    @inheritdoc
   *
   *    $willNotTerminateInf
   *
   *    Note: `xs.reverseMap(f)` is the same as `xs.reverse.map(f)` but might be more efficient.
   *
   *    @return       a new $coll resulting from applying the given function
   *                  `f` to each element of this $coll and collecting the results in reversed order.
   */
  def reverseMap[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That

  /** Tests whether this $coll starts with the given sequence.
   *
   * @param  that    the sequence to test
   * @return `true` if this collection has `that` as a prefix, `false` otherwise.
   */
  def startsWith[B](that: GenSeq[B]): Boolean = startsWith(that, 0)

  /** Tests whether this $coll contains the given sequence at a given index.
   *
   * '''Note''': If the both the receiver object `this` and the argument
   * `that` are infinite sequences this method may not terminate.
   *
   * @param  that    the sequence to test
   * @param  offset  the index where the sequence is searched.
   * @return `true` if the sequence `that` is contained in this $coll at
   *         index `offset`, otherwise `false`.
   */
  def startsWith[B](that: GenSeq[B], offset: Int): Boolean

  /** Tests whether this $coll ends with the given sequence.
   *  $willNotTerminateInf
   *  @param  that    the sequence to test
   *  @return `true` if this $coll has `that` as a suffix, `false` otherwise.
   */
  def endsWith[B](that: GenSeq[B]): Boolean

  /** Produces a new $coll where a slice of elements in this $coll is replaced by another sequence.
   *
   *  @param  from     the index of the first replaced element
   *  @param  patch    the replacement sequence
   *  @param  replaced the number of elements to drop in the original $coll
   *  @tparam B        the element type of the returned $coll.
   *  @tparam That     $thatinfo
   *  @param bf        $bfinfo
   *  @return          a new $coll consisting of all elements of this $coll
   *                   except that `replaced` elements starting from `from` are replaced
   *                   by `patch`.
   *
   *  @usecase def patch(from: Int, that: GenSeq[A], replaced: Int): $Coll[A]
   *    @inheritdoc
   *
   *    @return          a new $coll consisting of all elements of this $coll
   *                     except that `replaced` elements starting from `from` are replaced
   *                     by `patch`.
   */
  def patch[B >: A, That](from: Int, patch: GenSeq[B], replaced: Int)(implicit bf: CanBuildFrom[Repr, B, That]): That

  /** A copy of this $coll with one single replaced element.
   *  @param  index  the position of the replacement
   *  @param  elem   the replacing element
   *  @tparam B        the element type of the returned $coll.
   *  @tparam That     $thatinfo
   *  @param bf        $bfinfo
   *  @return a new $coll which is a copy of this $coll with the element at position `index` replaced by `elem`.
   *  @throws IndexOutOfBoundsException if `index` does not satisfy `0 <= index < length`.
   *
   *  @usecase def updated(index: Int, elem: A): $Coll[A]
   *    @inheritdoc
   *
   *    @return a copy of this $coll with the element at position `index` replaced by `elem`.
   */
  def updated[B >: A, That](index: Int, elem: B)(implicit bf: CanBuildFrom[Repr, B, That]): That

  /** A copy of the $coll with an element prepended.
   *
   *  @param  elem   the prepended element
   *  @tparam B      the element type of the returned $coll.
   *  @tparam That   $thatinfo
   *  @param bf      $bfinfo
   *  @return a new collection of type `That` consisting of `elem` followed
   *          by all elements of this $coll.
   *
   *  @usecase def +:(elem: A): $Coll[A]
   *    @inheritdoc
   *
   *    Note that :-ending operators are right associative (see example).
   *    A mnemonic for `+:` vs. `:+` is: the COLon goes on the COLlection side.
   *
   *    Also, the original $coll is not modified, so you will want to capture the result.
   *
   *    Example:
   *    {{{
   *      scala> val x = List(1)
   *      x: List[Int] = List(1)
   *
   *      scala> val y = 2 +: x
   *      y: List[Int] = List(2, 1)
   *
   *      scala> println(x)
   *      List(1)
   *    }}}
   *
   *    @return a new $coll consisting of `elem` followed
   *            by all elements of this $coll.
   */
  def +:[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Repr, B, That]): That

  /** A copy of this $coll with an element appended.
   *
   *  A mnemonic for `+:` vs. `:+` is: the COLon goes on the COLlection side.
   *
   *  @param  elem   the appended element
   *  @tparam B      the element type of the returned $coll.
   *  @tparam That   $thatinfo
   *  @param bf      $bfinfo
   *  @return a new collection of type `That` consisting of
   *          all elements of this $coll followed by `elem`.
   *
   *  @usecase def :+(elem: A): $Coll[A]
   *    @inheritdoc
   *
   *    $willNotTerminateInf
   *
   *    Example:
   *    {{{
   *       scala> val a = List(1)
   *       a: List[Int] = List(1)
   *       
   *       scala> val b = a :+ 2
   *       b: List[Int] = List(1, 2)
   *       
   *       scala> println(a)
   *       List(1)
   *    }}}
   *
   *    @return a new $coll consisting of
   *            all elements of this $coll followed by `elem`.
   */
  def :+[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Repr, B, That]): That

  /** A copy of this $coll with an element value appended until a given target length is reached.
   *
   *  @param   len   the target length
   *  @param   elem  the padding value
   *  @tparam B      the element type of the returned $coll.
   *  @tparam That   $thatinfo
   *  @param bf      $bfinfo
   *  @return a new collection of type `That` consisting of
   *          all elements of this $coll followed by the minimal number of occurrences of `elem` so
   *          that the resulting collection has a length of at least `len`.
   *  @usecase def padTo(len: Int, elem: A): $Coll[A]
   *    @inheritdoc
   *
   *    @return a new $coll consisting of
   *            all elements of this $coll followed by the minimal number of occurrences of `elem` so
   *            that the resulting $coll has a length of at least `len`.
   */
  def padTo[B >: A, That](len: Int, elem: B)(implicit bf: CanBuildFrom[Repr, B, That]): That

  /** Tests whether every element of this $coll relates to the
   *  corresponding element of another sequence by satisfying a test predicate.
   *
   *  @param   that  the other sequence
   *  @param   p     the test predicate, which relates elements from both sequences
   *  @tparam  B     the type of the elements of `that`
   *  @return  `true` if both sequences have the same length and
   *                  `p(x, y)` is `true` for all corresponding elements `x` of this $coll
   *                  and `y` of `that`, otherwise `false`.
   */
  def corresponds[B](that: GenSeq[B])(p: (A, B) => Boolean): Boolean

  def toSeq: GenSeq[A]

  /** Produces a new sequence which contains all elements of this $coll and also all elements of
   *  a given sequence. `xs union ys`  is equivalent to `xs ++ ys`.
   *
   *  @param that   the sequence to add.
   *  @tparam B     the element type of the returned $coll.
   *  @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 union(that: GenSeq[A]): $Coll[A]
   *    @inheritdoc
   *
   *    Another way to express this
   *    is that `xs union ys` computes the order-preserving multi-set union of `xs` and `ys`.
   *    `union` is hence a counter-part of `diff` and `intersect` which also work on multi-sets.
   *
   *    $willNotTerminateInf
   *
   *    @return       a new $coll which contains all elements of this $coll
   *                  followed by all elements of `that`.
   */
  def union[B >: A, That](that: GenSeq[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = this ++ that

  /** Computes the multiset difference between this $coll and another sequence.
   *
   *  @param that   the sequence of elements to remove
   *  @tparam B     the element type of the returned $coll.
   *  @return       a new collection of type `That` which contains all elements of this $coll
   *                except some of occurrences of elements that also appear in `that`.
   *                If an element value `x` appears
   *                ''n'' times in `that`, then the first ''n'' occurrences of `x` will not form
   *                part of the result, but any following occurrences will.
   *
   *  @usecase def diff(that: GenSeq[A]): $Coll[A]
   *    @inheritdoc
   *
   *    $willNotTerminateInf
   *
   *    @return       a new $coll which contains all elements of this $coll
   *                  except some of occurrences of elements that also appear in `that`.
   *                  If an element value `x` appears
   *                  ''n'' times in `that`, then the first ''n'' occurrences of `x` will not form
   *                  part of the result, but any following occurrences will.
   */
  def diff[B >: A](that: GenSeq[B]): Repr

  /** Computes the multiset intersection between this $coll and another sequence.
   *
   *  @param that   the sequence of elements to intersect with.
   *  @tparam B     the element type of the returned $coll.
   *  @return       a new collection of type `That` which contains all elements of this $coll
   *                which also appear in `that`.
   *                If an element value `x` appears
   *                ''n'' times in `that`, then the first ''n'' occurrences of `x` will be retained
   *                in the result, but any following occurrences will be omitted.
   *
   *  @usecase def intersect(that: GenSeq[A]): $Coll[A]
   *    @inheritdoc
   *
   *    $mayNotTerminateInf
   *
   *    @return       a new $coll which contains all elements of this $coll
   *                  which also appear in `that`.
   *                  If an element value `x` appears
   *                  ''n'' times in `that`, then the first ''n'' occurrences of `x` will be retained
   *                  in the result, but any following occurrences will be omitted.
   */
  def intersect[B >: A](that: GenSeq[B]): Repr

  /** Builds a new $coll from this $coll without any duplicate elements.
   *  $willNotTerminateInf
   *
   *  @return  A new $coll which contains the first occurrence of every element of this $coll.
   */
  def distinct: Repr

  /** Hashcodes for $Coll produce a value from the hashcodes of all the
   *  elements of the $coll.
   */
  override def hashCode()= scala.util.hashing.MurmurHash3.seqHash(seq)

  /** The equals method for arbitrary sequences. Compares this sequence to
   *  some other object.
   *  @param    that  The object to compare the sequence to
   *  @return   `true` if `that` is a sequence that has the same elements as
   *            this sequence in the same order, `false` otherwise
   */
  override def equals(that: Any): Boolean = that match {
    case that: GenSeq[_] => (that canEqual this) && (this sameElements that)
    case _               => false
  }

}