scala.collection.SeqLike

trait SeqLike[+A, +Repr] extends IterableLike[A, Repr] with GenSeqLike[A, Repr] with Parallelizable[A, ParSeq[A]]

A template trait for sequences of type Seq[A]

Sequences are special cases of iterable collections of class Iterable . Unlike iterables, sequences always have a defined order of elements. Sequences provide a method apply for indexing. Indices range from 0 up to the length of a sequence. Sequences support a number of methods to find occurrences of elements or subsequences, including segmentLength , prefixLength , indexWhere , indexOf , lastIndexWhere , lastIndexOf , startsWith , endsWith , indexOfSlice .

Another way to see a sequence is as a PartialFunction from Int values to the element type of the sequence. The isDefinedAt method of a sequence returns true for the interval from 0 until length .

Sequences can be accessed in reverse order of their elements, using methods reverse and reverseIterator .

Sequences have two principal subtraits, IndexedSeq and LinearSeq , which give different guarantees for performance. An IndexedSeq provides fast random-access of elements and a fast length operation. A LinearSeq provides fast access only to the first element via head , but also has a fast tail operation.

• Self Type
  • SeqLike [A, Repr]
• Source
  • SeqLike.scala - Blame
  • SeqLike.scala - History

Type Members

type Self = Repr

The type implementing this traversable

• Attributes
  • protected[this]
• Definition Classes
  • TraversableLike

class WithFilter extends FilterMonadic[A, Repr]

A class supporting filtered operations. Instances of this class are returned by method withFilter .

• Definition Classes
  • TraversableLike

Concrete Value Members From 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 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 sequence that is equal (as determined by == ) to elem , or -1 , if none exists.
• Definition Classes
  • GenSeqLike

(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 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 sequence that is equal (as determined by == ) to elem , or -1 , if none exists.
• Definition Classes
  • GenSeqLike

(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.
• Definition Classes
  • GenSeqLike

(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.
• Definition Classes
  • GenSeqLike

(defined at scala.collection.GenSeqLike)

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

[use case]

Finds index of last occurrence of some value in this 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 sequence that is equal (as determined by == ) to elem , or -1 , if none exists.
• Definition Classes
  • GenSeqLike

(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 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 sequence that is equal (as determined by == ) to elem , or -1 , if none exists.
• Definition Classes
  • GenSeqLike

(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.
• Definition Classes
  • GenSeqLike

(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 .
• Definition Classes
  • GenSeqLike

(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.
• Definition Classes
  • GenSeqLike

(defined at scala.collection.GenSeqLike)

Concrete Value Members From scala.collection.IterableLike

def canEqual(that: Any): Boolean

Method called from equality methods, so that user-defined subclasses can refuse to be equal to other collections of the same kind.

• that
  • The object with which this iterable collection should be compared
• returns
  • true , if this iterable collection can possibly equal that , false otherwise. The test takes into consideration only the run-time types of objects but ignores their elements.
• Definition Classes
  • IterableLike → Equals

(defined at scala.collection.IterableLike)

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

[use case]

Copies the elements of this sequence to an array. Fills the given array xs with at most len elements of this sequence, starting at position start . Copying will stop once either the end of the current 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
  • IterableLike → TraversableLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.IterableLike)

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 iterable collection.
• returns
  • a iterable collection consisting of all elements of this iterable collection except the first n ones, or else the empty iterable collection, if this iterable collection has less than n elements.
• Definition Classes
  • IterableLike → TraversableLike → GenTraversableLike

(defined at scala.collection.IterableLike)

def dropRight(n: Int): Repr

Selects all elements except last n ones.

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

• n
  • The number of elements to take
• returns
  • a iterable collection consisting of all elements of this iterable collection except the last n ones, or else the empty iterable collection, if this iterable collection has less than n elements.
• Definition Classes
  • IterableLike

(defined at scala.collection.IterableLike)

def exists(p: (A) ⇒ Boolean): Boolean

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

Note: may not terminate for infinite-sized collections.

• p
  • the predicate used to test elements.
• returns
  • false if this iterable collection is empty, otherwise true if the given predicate p holds for some of the elements of this iterable collection, otherwise false
• Definition Classes
  • IterableLike → TraversableLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.IterableLike)

def find(p: (A) ⇒ Boolean): Option[A]

Finds the first element of the iterable collection 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 iterable collection that satisfies p , or None if none exists.
• Definition Classes
  • IterableLike → TraversableLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.IterableLike)

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

Applies a binary operator to all elements of this iterable collection 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 iterable collection, 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 iterable collection. Returns
 `z` if this iterable collection is empty.

• Definition Classes
  • IterableLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.IterableLike)

def forall(p: (A) ⇒ Boolean): Boolean

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

Note: may not terminate for infinite-sized collections.

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

(defined at scala.collection.IterableLike)

def foreach[U](f: (A) ⇒ U): Unit

[use case]

Applies a function f to all elements of this sequence.

Note: this method underlies the implementation of most other bulk operations. Subclasses should re-implement this method if a more efficient implementation exists.

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

(defined at scala.collection.IterableLike)

def grouped(size: Int): Iterator[Repr]

Partitions elements in fixed size iterable collections.

• size
  • the number of elements per group
• returns
  • An iterator producing iterable collections of size size , except the last will be less than size size if the elements don’t divide evenly.
• Definition Classes
  • IterableLike
• See also
  • scala.collection.Iterator, method grouped

(defined at scala.collection.IterableLike)

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

Applies a binary operator to all elements of this iterable collection, 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 iterable collection, going right to left:

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

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

• Definition Classes
  • IterableLike → TraversableOnce → GenTraversableOnce
• Exceptions thrown
  • UnsupportedOperationException if this iterable collection is empty.

(defined at scala.collection.IterableLike)

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

[use case]

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

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
  • IterableLike → GenIterableLike

(defined at scala.collection.IterableLike)

def slice(from: Int, 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.

• returns
  • a iterable collection containing the elements greater than or equal to index from extending up to (but not including) index until of this iterable collection.
• Definition Classes
  • IterableLike → TraversableLike → GenTraversableLike

(defined at scala.collection.IterableLike)

def sliding(size: Int): Iterator[Repr]

Groups elements in fixed size blocks by passing a “sliding window” over them (as opposed to partitioning them, as is done in grouped.) “Sliding window” step is 1 by default.

• size
  • the number of elements per group
• returns
  • An iterator producing iterable collections of size size , except the last and the only element will be truncated if there are fewer elements than size.
• Definition Classes
  • IterableLike
• See also
  • scala.collection.Iterator, method sliding

(defined at scala.collection.IterableLike)

def sliding(size: Int, step: Int): Iterator[Repr]

Groups elements in fixed size blocks by passing a “sliding window” over them (as opposed to partitioning them, as is done in grouped.)

• size
  • the number of elements per group
• step
  • the distance between the first elements of successive groups
• returns
  • An iterator producing iterable collections of size size , except the last and the only element will be truncated if there are fewer elements than size.
• Definition Classes
  • IterableLike
• See also
  • scala.collection.Iterator, method sliding

(defined at scala.collection.IterableLike)

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 iterable collection.
• returns
  • a iterable collection consisting only of the first n elements of this iterable collection, or else the whole iterable collection, if it has less than n elements.
• Definition Classes
  • IterableLike → TraversableLike → GenTraversableLike

(defined at scala.collection.IterableLike)

def takeRight(n: Int): Repr

Selects last n elements.

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

• n
  • the number of elements to take
• returns
  • a iterable collection consisting only of the last n elements of this iterable collection, or else the whole iterable collection, if it has less than n elements.
• Definition Classes
  • IterableLike

(defined at scala.collection.IterableLike)

def takeWhile(p: (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.

• returns
  • the longest prefix of this iterable collection whose elements all satisfy the predicate p .
• Definition Classes
  • IterableLike → TraversableLike → GenTraversableLike

(defined at scala.collection.IterableLike)

def toStream: immutable.Stream[A]

Converts this iterable collection to a stream.

• returns
  • a stream containing all elements of this iterable collection.
• Definition Classes
  • IterableLike → TraversableLike → GenTraversableOnce

(defined at scala.collection.IterableLike)

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 sequence formed from this 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.

• 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 sequence is shorter than that .
• thatElem
  • the element to be used to fill up the result if that is shorter than this sequence.
• returns
  • a new sequence containing pairs consisting of corresponding elements of this sequence and that . The length of the returned collection is the maximum of the lengths of this sequence and that . If this sequence is shorter than that , thisElem values are used to pad the result. If that is shorter than this sequence, thatElem values are used to pad the result.
• Definition Classes
  • IterableLike → GenIterableLike

(defined at scala.collection.IterableLike)

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

[use case]

Returns a sequence formed from this 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.

• 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 sequence containing pairs consisting of corresponding elements of this sequence and that . The length of the returned collection is the minimum of the lengths of this sequence and that .
• Definition Classes
  • IterableLike → GenIterableLike

(defined at scala.collection.IterableLike)

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)

Abstract Value Members From scala.collection.SeqLike

abstract def apply(idx: Int): A

Selects an element by its index in the 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 sequence at index idx , where 0 indicates the first element.
• Definition Classes
  • SeqLike → GenSeqLike
• Exceptions thrown
  • IndexOutOfBoundsException if idx does not satisfy 0 <= idx < length .

(defined at scala.collection.SeqLike)

Concrete Value Members From scala.collection.SeqLike

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

[use case]

A copy of the 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 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 sequence consisting of elem followed by all elements of this sequence.
• Definition Classes
  • SeqLike → GenSeqLike

(defined at scala.collection.SeqLike)

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

[use case]

A copy of this 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 sequence consisting of all elements of this sequence followed by elem .
• Definition Classes
  • SeqLike → GenSeqLike

(defined at scala.collection.SeqLike)

def combinations(n: Int): Iterator[Repr]

Iterates over combinations. A combination of length n is a subsequence of the original sequence, with the elements taken in order. Thus, "xy" and "yy" are both length-2 combinations of "xyy" , but "yx" is not. If there is more than one way to generate the same subsequence, only one will be returned.

For example, "xyyy" has three different ways to generate "xy" depending on whether the first, second, or third "y" is selected. However, since all are identical, only one will be chosen. Which of the three will be taken is an implementation detail that is not defined.

• returns
  • An Iterator which traverses the possible n-element combinations of this sequence.

Example:

"abbbc".combinations(2) = Iterator(ab, ac, bb, bc)

(defined at scala.collection.SeqLike)

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

Tests whether this sequence contains a given sequence as a slice.

Note: may not terminate for infinite-sized collections.

• that
  • the sequence to test
• returns
  • true if this sequence contains a slice with the same elements as that , otherwise false .

(defined at scala.collection.SeqLike)

def contains[A1 >: A](elem: A1): Boolean

Tests whether this sequence contains a given value as an element.

Note: may not terminate for infinite-sized collections.

• elem
  • the element to test.
• returns
  • true if this sequence has an element that is equal (as determined by == ) to elem , false otherwise.

(defined at scala.collection.SeqLike)

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

Tests whether every element of this 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 sequence and y of that , otherwise false .
• Definition Classes
  • SeqLike → GenSeqLike

(defined at scala.collection.SeqLike)

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

[use case]

Computes the multiset difference between this sequence and another sequence.

Note: will not terminate for infinite-sized collections.

• that
  • the sequence of elements to remove
• returns
  • a new sequence which contains all elements of this 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.
• Definition Classes
  • SeqLike → GenSeqLike

(defined at scala.collection.SeqLike)

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

Tests whether this sequence ends with the given sequence.

Note: will not terminate for infinite-sized collections.

• that
  • the sequence to test
• returns
  • true if this sequence has that as a suffix, false otherwise.
• Definition Classes
  • SeqLike → GenSeqLike

(defined at scala.collection.SeqLike)

def indexOfSlice[B >: A](that: GenSeq[B]): Int

Finds first index where this sequence contains a given sequence as a slice.

Note: may not terminate for infinite-sized collections.

• that
  • the sequence to test
• returns
  • the first index such that the elements of this sequence starting at this index match the elements of sequence that , or -1 of no such subsequence exists.

(defined at scala.collection.SeqLike)

def indexOfSlice[B >: A](that: GenSeq[B], from: Int): Int

Finds first index after or at a start index where this sequence contains a given sequence as a slice.

Note: may not terminate for infinite-sized collections.

• that
  • the sequence to test
• from
  • the start index
• returns
  • the first index >= from such that the elements of this sequence starting at this index match the elements of sequence that , or -1 of no such subsequence exists.

(defined at scala.collection.SeqLike)

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 sequence that satisfies the predicate p , or -1 , if none exists.
• Definition Classes
  • SeqLike → GenSeqLike

(defined at scala.collection.SeqLike)

def indices: immutable.Range

Produces the range of all indices of this sequence.

• returns
  • a Range value from 0 to one less than the length of this sequence.

(defined at scala.collection.SeqLike)

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

[use case]

Computes the multiset intersection between this sequence and another sequence.

Note: may not terminate for infinite-sized collections.

• that
  • the sequence of elements to intersect with.
• returns
  • a new sequence which contains all elements of this 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.
• Definition Classes
  • SeqLike → GenSeqLike

(defined at scala.collection.SeqLike)

def lastIndexOfSlice[B >: A](that: GenSeq[B]): Int

Finds last index where this sequence contains a given sequence as a slice.

Note: will not terminate for infinite-sized collections.

• that
  • the sequence to test
• returns
  • the last index such that the elements of this sequence starting a this index match the elements of sequence that , or -1 of no such subsequence exists.

(defined at scala.collection.SeqLike)

def lastIndexOfSlice[B >: A](that: GenSeq[B], end: Int): Int

Finds last index before or at a given end index where this sequence contains a given sequence as a slice.

• that
  • the sequence to test
• end
  • the end index
• returns
  • the last index <= end such that the elements of this sequence starting at this index match the elements of sequence that , or -1 of no such subsequence exists.

(defined at scala.collection.SeqLike)

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 sequence that satisfies the predicate p , or -1 , if none exists.
• Definition Classes
  • SeqLike → GenSeqLike

(defined at scala.collection.SeqLike)

def lengthCompare(len: Int): Int

Compares the length of this sequence to a test value.

• len
  • the test value that gets compared with the length.
• returns
  • A value x where

    x <  0       if this.length <  len
    x == 0       if this.length == len
    x >  0       if this.length >  len
    

The method as implemented here does not call `length` directly; its running
time is `O(length min len)` instead of `O(length)` . The method should be
overwritten if computing `length` is cheap.

(defined at scala.collection.SeqLike)

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

[use case]

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

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

(defined at scala.collection.SeqLike)

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
  • SeqLike → TraversableLike → Parallelizable

(defined at scala.collection.SeqLike)

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

[use case]

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

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

(defined at scala.collection.SeqLike)

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 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 sequence resulting from applying the given function f to each element of this sequence and collecting the results in reversed order.
• Definition Classes
  • SeqLike → GenSeqLike

(defined at scala.collection.SeqLike)

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 sequence starting from index from such that every element of the segment satisfies the predicate p .
• Definition Classes
  • SeqLike → GenSeqLike

(defined at scala.collection.SeqLike)

def sortBy[B](f: (A) ⇒ B)(implicit ord: math.Ordering[B]): Repr

Sorts this Seq according to the Ordering which results from transforming an implicitly given Ordering with a transformation function.

• B
  • the target type of the transformation f , and the type where the ordering ord is defined.
• f
  • the transformation function mapping elements to some other domain B .
• ord
  • the ordering assumed on domain B .
• returns
  • a sequence consisting of the elements of this sequence sorted according to the ordering where x < y if ord.lt(f(x), f(y)) .
• See also
  • scala.math.Ordering Note: will not terminate for infinite-sized collections.

Example:

val words = "The quick brown fox jumped over the lazy dog".split(' ')
// this works because scala.Ordering will implicitly provide an Ordering[Tuple2[Int, Char]]
words.sortBy(x => (x.length, x.head))
res0: Array[String] = Array(The, dog, fox, the, lazy, over, brown, quick, jumped)

(defined at scala.collection.SeqLike)

def sortWith(lt: (A, A) ⇒ Boolean): Repr

Sorts this sequence according to a comparison function.

Note: will not terminate for infinite-sized collections.

The sort is stable. That is, elements that are equal (as determined by lt ) appear in the same order in the sorted sequence as in the original.

• lt
  • the comparison function which tests whether its first argument precedes its second argument in the desired ordering.
• returns
  • a sequence consisting of the elements of this sequence sorted according to the comparison function lt .

Example:

List("Steve", "Tom", "John", "Bob").sortWith(_.compareTo(_) < 0) =
List("Bob", "John", "Steve", "Tom")

(defined at scala.collection.SeqLike)

def sorted[B >: A](implicit ord: math.Ordering[B]): Repr

Sorts this sequence according to an Ordering.

The sort is stable. That is, elements that are equal (as determined by lt ) appear in the same order in the sorted sequence as in the original.

• ord
  • the ordering to be used to compare elements.
• returns
  • a sequence consisting of the elements of this sequence sorted according to the ordering ord .
• See also
  • scala.math.Ordering

(defined at scala.collection.SeqLike)

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

Tests whether this 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 sequence at index offset , otherwise false .
• Definition Classes
  • SeqLike → GenSeqLike

(defined at scala.collection.SeqLike)

def toCollection(repr: Repr): Seq[A]

A conversion from collections of type Repr to Seq objects. By default this is implemented as just a cast, but this can be overridden.

• Attributes
  • protected[this]
• Definition Classes
  • SeqLike → IterableLike → TraversableLike

(defined at scala.collection.SeqLike)

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 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 sequence which contains all elements of this sequence followed by all elements of that .
• Definition Classes
  • SeqLike → GenSeqLike

(defined at scala.collection.SeqLike)

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

[use case]

A copy of this sequence with one single replaced element.

• index
  • the position of the replacement
• elem
  • the replacing element
• returns
  • a copy of this sequence with the element at position index replaced by elem .
• Definition Classes
  • SeqLike → GenSeqLike

(defined at scala.collection.SeqLike)

def view(from: Int, until: Int): SeqView[A, Repr]

Creates a non-strict view of a slice of this sequence.

Note: the difference between view and slice is that view produces a view of the current sequence, whereas slice produces a new sequence.

Note: view(from, to) is equivalent to view.slice(from, to)

• from
  • the index of the first element of the view
• until
  • the index of the element following the view
• returns
  • a non-strict view of a slice of this sequence, starting at index from and extending up to (but not including) index until .
• Definition Classes
  • SeqLike → IterableLike → TraversableLike

(defined at scala.collection.SeqLike)

def view: SeqView[A, Repr]

Creates a non-strict view of this sequence.

• returns
  • a non-strict view of this sequence.
• Definition Classes
  • SeqLike → IterableLike → TraversableLike

(defined at scala.collection.SeqLike)

Abstract Value Members From scala.collection.TraversableLike

abstract def newBuilder: Builder[A, Repr]

Creates a new builder for this collection type.

• Attributes
  • protected[this]
• Definition Classes
  • TraversableLike → HasNewBuilder

(defined at scala.collection.TraversableLike)

Concrete Value Members From scala.collection.TraversableLike

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

As with ++ , returns a new collection containing the elements from the left operand followed by the elements from the right operand.

It differs from ++ in that the right operand determines the type of the resulting collection rather than the left one. Mnemonic: the COLon is on the side of the new COLlection type.

Example:

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

scala> val y = LinkedList(2)
y: scala.collection.mutable.LinkedList[Int] = LinkedList(2)

scala> val z = x ++: y
z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)

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.

• B
  • the element type of the returned collection.
• That
  • the class of the returned collection. Where possible, That is the same class as the current collection class Repr , but this depends on the element type B being admissible for that class, which means that an implicit instance of type CanBuildFrom[Repr, B, That] is found.
• that
  • the traversable to append.
• 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
  • a new collection of type That which contains all elements of this traversable collection followed by all elements of that .
• Definition Classes
  • TraversableLike

(defined at scala.collection.TraversableLike)

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

[use case]

As with ++ , returns a new collection containing the elements from the left operand followed by the elements from the right operand.

It differs from ++ in that the right operand determines the type of the resulting collection rather than the left one. Mnemonic: the COLon is on the side of the new COLlection type.

Example:

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

scala> val y = LinkedList(2)
y: scala.collection.mutable.LinkedList[Int] = LinkedList(2)

scala> val z = x ++: y
z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)

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

(defined at scala.collection.TraversableLike)

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

[use case]

Returns a new sequence containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the 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 sequence which contains all elements of this sequence followed by all elements of that .
• Definition Classes
  • TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableLike)

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 sequence on which the function is defined.

• B
  • the element type of the returned collection.
• pf
  • the partial function which filters and maps the sequence.
• returns
  • a new 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
  • TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableLike)

def dropWhile(p: (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.

• returns
  • the longest suffix of this traversable collection whose first element does not satisfy the predicate p .
• Definition Classes
  • TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableLike)

def filter(p: (A) ⇒ Boolean): Repr

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

• p
  • the predicate used to test elements.
• returns
  • a new traversable collection consisting of all elements of this traversable collection that satisfy the given predicate p . The order of the elements is preserved.
• Definition Classes
  • TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableLike)

def filterNot(p: (A) ⇒ Boolean): Repr

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

• p
  • the predicate used to test elements.
• returns
  • a new traversable collection consisting of all elements of this traversable collection that do not satisfy the given predicate p . The order of the elements is preserved.
• Definition Classes
  • TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableLike)

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 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 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 sequence resulting from applying the given collection-valued function f to each element of this sequence and concatenating the results.
• Definition Classes
  • TraversableLike → GenTraversableLike → FilterMonadic

(defined at scala.collection.TraversableLike)

def groupBy[K](f: (A) ⇒ K): immutable.Map[K, Repr]

Partitions this traversable collection into a map of traversable 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 traversable collection.

• K
  • the type of keys returned by the discriminator function.
• f
  • the discriminator function.
• returns
  • A map from keys to traversable 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 traversable collection of those
elements `x` for which `f(x)` equals `k` .

• Definition Classes
  • TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableLike)

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 sequence.

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

(defined at scala.collection.TraversableLike)

def partition(p: (A) ⇒ Boolean): (Repr, Repr)

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

• p
  • the predicate on which to partition.
• returns
  • a pair of traversable collections: the first traversable collection consists of all elements that satisfy the predicate p and the second traversable collection consists of all elements that don’t. The relative order of the elements in the resulting traversable collections is the same as in the original traversable collection.
• Definition Classes
  • TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableLike)

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
  • TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableLike)

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
  • TraversableLike → 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.TraversableLike)

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 traversable collection containing the prefix scan of the elements in this traversable collection
• Definition Classes
  • TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableLike)

def span(p: (A) ⇒ Boolean): (Repr, Repr)

Splits this traversable 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.

• returns
  • a pair consisting of the longest prefix of this traversable collection whose elements all satisfy p , and the rest of this traversable collection.
• Definition Classes
  • TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableLike)

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

Splits this traversable 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 traversable collections consisting of the first n elements of this traversable collection, and the other elements.
• Definition Classes
  • TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableLike)

def withFilter(p: (A) ⇒ Boolean): FilterMonadic[A, Repr]

Creates a non-strict filter of this traversable collection.

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.

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

• p
  • the predicate used to test elements.
• returns
  • an object of class WithFilter , which supports map , flatMap , foreach , and withFilter operations. All these operations apply to those elements of this traversable collection which satisfy the predicate p .
• Definition Classes
  • TraversableLike → FilterMonadic

(defined at scala.collection.TraversableLike)

Concrete Value Members From scala.collection.TraversableOnce

def /:[B](z: B)(op: (B, A) ⇒ B): B

Applies a binary operator to a start value and all elements of this traversable 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 traversable 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 traversable or iterator.

• Definition Classes
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

def :\[B](z: B)(op: (A, B) ⇒ B): B

Applies a binary operator to all elements of this traversable 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 traversable 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 traversable or iterator.

• Definition Classes
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

def addString(b: StringBuilder): StringBuilder

Appends all elements of this traversable or iterator to a string builder. The written text consists of the string representations (w.r.t. the method toString ) of all elements of this traversable or iterator without any separator string.

Example:

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

scala> val b = new StringBuilder()
b: StringBuilder =

scala> val h = a.addString(b)
h: StringBuilder = 1234

• b
  • the string builder to which elements are appended.
• returns
  • the string builder b to which elements were appended.
• Definition Classes
  • TraversableOnce

(defined at scala.collection.TraversableOnce)

def addString(b: StringBuilder, sep: String): StringBuilder

Appends all elements of this traversable or iterator to a string builder using a separator string. The written text consists of the string representations (w.r.t. the method toString ) of all elements of this traversable or iterator, separated by the string sep .

Example:

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

scala> val b = new StringBuilder()
b: StringBuilder =

scala> a.addString(b, ", ")
res0: StringBuilder = 1, 2, 3, 4

• b
  • the string builder to which elements are appended.
• sep
  • the separator string.
• returns
  • the string builder b to which elements were appended.
• Definition Classes
  • TraversableOnce

(defined at scala.collection.TraversableOnce)

def addString(b: StringBuilder, start: String, sep: String, end: String): StringBuilder

Appends all elements of this traversable or iterator to a string builder using start, end, and separator strings. The written text 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 traversable or iterator are separated by the string sep .

Example:

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

scala> val b = new StringBuilder()
b: StringBuilder =

scala> a.addString(b , "List(" , ", " , ")")
res5: StringBuilder = List(1, 2, 3, 4)

• b
  • the string builder to which elements are appended.
• start
  • the starting string.
• sep
  • the separator string.
• end
  • the ending string.
• returns
  • the string builder b to which elements were appended.
• Definition Classes
  • TraversableOnce

(defined at scala.collection.TraversableOnce)

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 traversable 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
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

def collectFirst[B](pf: PartialFunction[A, B]): Option[B]

Finds the first element of the traversable or iterator for which the given partial function is defined, and applies the partial function to it.

Note: may not terminate for infinite-sized collections.

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

• pf
  • the partial function
• returns
  • an option value containing pf applied to the first value for which it is defined, or None if none exists.
• Definition Classes
  • TraversableOnce

Example:

Seq("a", 1, 5L).collectFirst({ case x: Int => x*10 }) = Some(10)

(defined at scala.collection.TraversableOnce)

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

[use case]

Copies the elements of this sequence to an array. Fills the given array xs with values of this sequence. Copying will stop once either the end of the current 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
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

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

[use case]

Copies the elements of this sequence to an array. Fills the given array xs with values of this sequence, beginning at index start . Copying will stop once either the end of the current 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
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

def copyToBuffer[B >: A](dest: Buffer[B]): Unit

Copies all elements of this traversable or iterator to a buffer.

Note: will not terminate for infinite-sized collections.

• dest
  • The buffer to which elements are copied.
• Definition Classes
  • TraversableOnce

(defined at scala.collection.TraversableOnce)

def count(p: (A) ⇒ Boolean): Int

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

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

(defined at scala.collection.TraversableOnce)

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

Applies a binary operator to a start value and all elements of this traversable 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 traversable 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 traversable or iterator.
Returns `z` if this traversable or iterator is empty.

• Definition Classes
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

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

Folds the elements of this traversable 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 traversable or iterator is empty.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

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 sequence with the largest value measured by function f.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

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 sequence with the smallest value measured by function f.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

def mkString(sep: String): String

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

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

Example:

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

(defined at scala.collection.TraversableOnce)

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

Displays all elements of this traversable 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 traversable 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 traversable or iterator are separated by the string sep .
• Definition Classes
  • TraversableOnce → GenTraversableOnce

Example:

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

(defined at scala.collection.TraversableOnce)

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

Optionally applies a binary operator to all elements of this traversable 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 traversable or iterator is nonempty, None otherwise.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

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

Applies a binary operator to all elements of this traversable 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
  • the result of inserting op between consecutive elements of this traversable or iterator, going left to right:

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

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

• Definition Classes
  • TraversableOnce
• Exceptions thrown
  • UnsupportedOperationException if this traversable or iterator is empty.

(defined at scala.collection.TraversableOnce)

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

Reduces the elements of this traversable 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
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

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

Optionally applies a binary operator to all elements of this traversable 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 traversable or iterator is nonempty, None otherwise.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

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

Reduces the elements of this traversable 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 traversable or iterator is nonempty.
• Definition Classes
  • TraversableOnce → GenTraversableOnce
• Exceptions thrown
  • UnsupportedOperationException if this traversable or iterator is empty.

(defined at scala.collection.TraversableOnce)

def toBuffer[B >: A]: Buffer[B]

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

Note: will not terminate for infinite-sized collections.

• returns
  • a buffer containing all elements of this traversable or iterator.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

def toIndexedSeq: immutable.IndexedSeq[A]

Converts this traversable or iterator to an indexed sequence.

Note: will not terminate for infinite-sized collections.

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

(defined at scala.collection.TraversableOnce)

def toMap[T, U](implicit ev: <:<[A, (T, U)]): immutable.Map[T, U]

[use case]

Converts this 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 sequence.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

def toSet[B >: A]: immutable.Set[B]

Converts this traversable or iterator to a set.

Note: will not terminate for infinite-sized collections.

• returns
  • a set containing all elements of this traversable or iterator.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

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

def toParArray: ParArray[T]

• Implicit information
  • This member is added by an implicit conversion from SeqLike [A, Repr] to CollectionsHaveToParArray [SeqLike [A, Repr], T] performed by method CollectionsHaveToParArray in scala.collection.parallel. This conversion will take place only if an implicit value of type (SeqLike [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 immutable.{ List, Range }
import generic._
import parallel.ParSeq
import scala.math.Ordering

/** A template trait for sequences of type `Seq[A]`
 *  $seqInfo
 *
 *  @define seqInfo
 *  Sequences are special cases of iterable collections of class `Iterable`.
 *  Unlike iterables, sequences always have a defined order of elements.
 *  Sequences provide a method `apply` for indexing. Indices range from `0` up to the `length` of
 *  a sequence. Sequences support a number of methods to find occurrences of elements or subsequences, including
 *  `segmentLength`, `prefixLength`, `indexWhere`, `indexOf`, `lastIndexWhere`, `lastIndexOf`,
 *  `startsWith`, `endsWith`, `indexOfSlice`.
 *
 *  Another way to see a sequence is as a `PartialFunction` from `Int` values
 *  to the element type of the sequence. The `isDefinedAt` method of a sequence
 *  returns `true` for the interval from `0` until `length`.
 *
 *  Sequences can be accessed in reverse order of their elements, using methods
 *  `reverse` and `reverseIterator`.
 *
 *  Sequences have two principal subtraits, `IndexedSeq` and `LinearSeq`, which give different guarantees for performance.
 *  An `IndexedSeq` provides fast random-access of elements and a fast `length` operation.
 *  A `LinearSeq` provides fast access only to the first element via `head`, but also
 *  has a fast `tail` operation.
 *
 *  @tparam A    the element type of the collection
 *  @tparam Repr the type of the actual collection containing the elements.
 *
 *  @author  Martin Odersky
 *  @author  Matthias Zenger
 *  @version 1.0, 16/07/2003
 *  @since   2.8
 *
 *  @define Coll `Seq`
 *  @define coll sequence
 *  @define thatinfo the class of the returned collection. Where possible, `That` is
 *    the same class as the current collection class `Repr`, but this
 *    depends on the element type `B` being admissible for that class,
 *    which means that an implicit instance of type `CanBuildFrom[Repr, B, That]`
 *    is found.
 *  @define bfinfo an implicit value of class `CanBuildFrom` which determines the
 *    result class `That` from the current representation type `Repr`
 *    and the new element type `B`.
 *  @define orderDependent
 *  @define orderDependentFold
 */
trait SeqLike[+A, +Repr] extends Any with IterableLike[A, Repr] with GenSeqLike[A, Repr] with Parallelizable[A, ParSeq[A]] { self =>

  override protected[this] def thisCollection: Seq[A] = this.asInstanceOf[Seq[A]]
  override protected[this] def toCollection(repr: Repr): Seq[A] = repr.asInstanceOf[Seq[A]]

  def length: Int

  def apply(idx: Int): A

  protected[this] override def parCombiner = ParSeq.newCombiner[A]

  /** Compares the length of this $coll to a test value.
   *
   *   @param   len   the test value that gets compared with the length.
   *   @return  A value `x` where
   *   {{{
   *        x <  0       if this.length <  len
   *        x == 0       if this.length == len
   *        x >  0       if this.length >  len
   *   }}}
   *  The method as implemented here does not call `length` directly; its running time
   *  is `O(length min len)` instead of `O(length)`. The method should be overwritten
   *  if computing `length` is cheap.
   */
  def lengthCompare(len: Int): Int = {
    if (len < 0) 1
    else {
      var i = 0
      val it = iterator
      while (it.hasNext) {
        if (i == len) return if (it.hasNext) 1 else 0
        it.next()
        i += 1
      }
      i - len
    }
  }

  override /*IterableLike*/ def isEmpty: Boolean = lengthCompare(0) == 0

  /** The size of this $coll, equivalent to `length`.
   *
   *  $willNotTerminateInf
   */
  override def size = length

  def segmentLength(p: A => Boolean, from: Int): Int = {
    var i = 0
    val it = iterator.drop(from)
    while (it.hasNext && p(it.next()))
      i += 1
    i
  }

  def indexWhere(p: A => Boolean, from: Int): Int = {
    var i = from
    val it = iterator.drop(from)
    while (it.hasNext) {
      if (p(it.next())) return i
      else i += 1
    }

    -1
  }

  def lastIndexWhere(p: A => Boolean, end: Int): Int = {
    var i = length - 1
    val it = reverseIterator
    while (it.hasNext && { val elem = it.next(); (i > end || !p(elem)) }) i -= 1
    i
  }

  /** Iterates over distinct permutations.
   *
   *  @return   An Iterator which traverses the distinct permutations of this $coll.
   *  @example  `"abb".permutations = Iterator(abb, bab, bba)`
   */
  def permutations: Iterator[Repr] =
    if (isEmpty) Iterator(repr)
    else new PermutationsItr

  /** Iterates over combinations.  A _combination_ of length `n` is a subsequence of
   *  the original sequence, with the elements taken in order.  Thus, `"xy"` and `"yy"`
   *  are both length-2 combinations of `"xyy"`, but `"yx"` is not.  If there is
   *  more than one way to generate the same subsequence, only one will be returned.
   *
   *  For example, `"xyyy"` has three different ways to generate `"xy"` depending on
   *  whether the first, second, or third `"y"` is selected.  However, since all are
   *  identical, only one will be chosen.  Which of the three will be taken is an
   *  implementation detail that is not defined.
   *
   *  @return   An Iterator which traverses the possible n-element combinations of this $coll.
   *  @example  `"abbbc".combinations(2) = Iterator(ab, ac, bb, bc)`
   */
  def combinations(n: Int): Iterator[Repr] =
    if (n < 0 || n > size) Iterator.empty
    else new CombinationsItr(n)

  private class PermutationsItr extends AbstractIterator[Repr] {
    private[this] val (elms, idxs) = init()
    private var _hasNext = true

    def hasNext = _hasNext
    def next(): Repr = {
      if (!hasNext)
        Iterator.empty.next()

      val forcedElms = new mutable.ArrayBuffer[A](elms.size) ++= elms
      val result = (self.newBuilder ++= forcedElms).result()
      var i = idxs.length - 2
      while(i >= 0 && idxs(i) >= idxs(i+1))
        i -= 1

      if (i < 0)
        _hasNext = false
      else {
        var j = idxs.length - 1
        while(idxs(j) <= idxs(i)) j -= 1
          swap(i,j)

        val len = (idxs.length - i) / 2
        var k = 1
        while (k <= len) {
          swap(i+k, idxs.length - k)
          k += 1
        }
      }
      result
    }
    private def swap(i: Int, j: Int) {
      val tmpI = idxs(i)
      idxs(i) = idxs(j)
      idxs(j) = tmpI
      val tmpE = elms(i)
      elms(i) = elms(j)
      elms(j) = tmpE
    }

    private[this] def init() = {
      val m = mutable.HashMap[A, Int]()
      val (es, is) = (thisCollection map (e => (e, m.getOrElseUpdate(e, m.size))) sortBy (_._2)).unzip

      (es.toBuffer, is.toArray)
    }
  }

  private class CombinationsItr(n: Int) extends AbstractIterator[Repr] {
    // generating all nums such that:
    // (1) nums(0) + .. + nums(length-1) = n
    // (2) 0 <= nums(i) <= cnts(i), where 0 <= i <= cnts.length-1
    private val (elms, cnts, nums) = init()
    private val offs = cnts.scanLeft(0)(_ + _)
    private var _hasNext = true

    def hasNext = _hasNext
    def next(): Repr = {
      if (!hasNext)
        Iterator.empty.next()

      /* Calculate this result. */
      val buf = self.newBuilder
      for(k <- 0 until nums.length; j <- 0 until nums(k))
        buf += elms(offs(k)+j)
      val res = buf.result()

      /* Prepare for the next call to next. */
      var idx = nums.length - 1
      while (idx >= 0 && nums(idx) == cnts(idx))
        idx -= 1

      idx = nums.lastIndexWhere(_ > 0, idx - 1)

      if (idx < 0)
        _hasNext = false
      else {
        var sum = nums.slice(idx + 1, nums.length).sum + 1
        nums(idx) -= 1
        for (k <- (idx+1) until nums.length) {
          nums(k) = sum min cnts(k)
          sum -= nums(k)
        }
      }

      res
    }

    /** Rearrange seq to newSeq a0a0..a0a1..a1...ak..ak such that
     *  seq.count(_ == aj) == cnts(j)
     *
     *  @return     (newSeq,cnts,nums)
     */
    private def init(): (IndexedSeq[A], Array[Int], Array[Int]) = {
      val m = mutable.HashMap[A, Int]()

      // e => (e, weight(e))
      val (es, is) = (thisCollection map (e => (e, m.getOrElseUpdate(e, m.size))) sortBy (_._2)).unzip
      val cs = new Array[Int](m.size)
      is foreach (i => cs(i) += 1)
      val ns = new Array[Int](cs.length)

      var r = n
      0 until ns.length foreach { k =>
        ns(k) = r min cs(k)
        r -= ns(k)
      }
      (es.toIndexedSeq, cs, ns)
    }
  }

  def reverse: Repr = {
    var xs: List[A] = List()
    for (x <- this)
      xs = x :: xs
    val b = newBuilder
    b.sizeHint(this)
    for (x <- xs)
      b += x
    b.result()
  }

  def reverseMap[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
    var xs: List[A] = List()
    for (x <- this)
      xs = x :: xs
    val b = bf(repr)
    for (x <- xs)
      b += f(x)

    b.result()
  }

  /** An iterator yielding elements in reversed order.
   *
   *   $willNotTerminateInf
   *
   * Note: `xs.reverseIterator` is the same as `xs.reverse.iterator` but might be more efficient.
   *
   *  @return  an iterator yielding the elements of this $coll in reversed order
   */
  def reverseIterator: Iterator[A] = toCollection(reverse).iterator

  def startsWith[B](that: GenSeq[B], offset: Int): Boolean = {
    val i = this.iterator drop offset
    val j = that.iterator
    while (j.hasNext && i.hasNext)
      if (i.next != j.next)
        return false

    !j.hasNext
  }

  def endsWith[B](that: GenSeq[B]): Boolean = {
    val i = this.iterator.drop(length - that.length)
    val j = that.iterator
    while (i.hasNext && j.hasNext)
      if (i.next != j.next)
        return false

    !j.hasNext
  }

  /** Finds first index where this $coll contains a given sequence as a slice.
   *  $mayNotTerminateInf
   *  @param  that    the sequence to test
   *  @return  the first index such that the elements of this $coll starting at this index
   *           match the elements of sequence `that`, or `-1` of no such subsequence exists.
   */
  def indexOfSlice[B >: A](that: GenSeq[B]): Int = indexOfSlice(that, 0)

  /** Finds first index after or at a start index where this $coll contains a given sequence as a slice.
   *  $mayNotTerminateInf
   *  @param  that    the sequence to test
   *  @param  from    the start index
   *  @return  the first index `>= from` such that the elements of this $coll starting at this index
   *           match the elements of sequence `that`, or `-1` of no such subsequence exists.
   */
  def indexOfSlice[B >: A](that: GenSeq[B], from: Int): Int =
    if (this.hasDefiniteSize && that.hasDefiniteSize) {
      val l = length
      val tl = that.length
      val clippedFrom = math.max(0, from)
      if (from > l) -1
      else if (tl < 1) clippedFrom
      else if (l < tl) -1
      else SeqLike.kmpSearch(thisCollection, clippedFrom, l, that.seq, 0, tl, forward = true)
    }
    else {
      var i = from
      var s: Seq[A] = thisCollection drop i
      while (!s.isEmpty) {
        if (s startsWith that)
          return i

        i += 1
        s = s.tail
      }
      -1
    }

  /** Finds last index where this $coll contains a given sequence as a slice.
   *  $willNotTerminateInf
   *  @param  that    the sequence to test
   *  @return  the last index such that the elements of this $coll starting a this index
   *           match the elements of sequence `that`, or `-1` of no such subsequence exists.
   */
  def lastIndexOfSlice[B >: A](that: GenSeq[B]): Int = lastIndexOfSlice(that, length)

  /** Finds last index before or at a given end index where this $coll contains a given sequence as a slice.
   *  @param  that    the sequence to test
   *  @param  end     the end index
   *  @return  the last index `<= end` such that the elements of this $coll starting at this index
   *           match the elements of sequence `that`, or `-1` of no such subsequence exists.
   */
  def lastIndexOfSlice[B >: A](that: GenSeq[B], end: Int): Int = {
    val l = length
    val tl = that.length
    val clippedL = math.min(l-tl, end)

    if (end < 0) -1
    else if (tl < 1) clippedL
    else if (l < tl) -1
    else SeqLike.kmpSearch(thisCollection, 0, clippedL+tl, that.seq, 0, tl, forward = false)
  }

  /** Tests whether this $coll contains a given sequence as a slice.
   *  $mayNotTerminateInf
   *  @param  that    the sequence to test
   *  @return  `true` if this $coll contains a slice with the same elements
   *           as `that`, otherwise `false`.
   */
  def containsSlice[B](that: GenSeq[B]): Boolean = indexOfSlice(that) != -1

  /** Tests whether this $coll contains a given value as an element.
   *  $mayNotTerminateInf
   *
   *  @param elem  the element to test.
   *  @return     `true` if this $coll has an element that is equal (as
   *              determined by `==`) to `elem`, `false` otherwise.
   */
  def contains[A1 >: A](elem: A1): Boolean = exists (_ == elem)

  /** 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: Seq[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`.
   */
  override 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: Seq[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 = {
    val occ = occCounts(that.seq)
    val b = newBuilder
    for (x <- this) {
      val ox = occ(x)  // Avoid multiple map lookups
      if (ox == 0) b += x
      else occ(x) = ox - 1
    }
    b.result()
  }

  /** 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: Seq[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 = {
    val occ = occCounts(that.seq)
    val b = newBuilder
    for (x <- this) {
      val ox = occ(x)  // Avoid multiple map lookups
      if (ox > 0) {
        b += x
        occ(x) = ox - 1
      }
    }
    b.result()
  }

  private def occCounts[B](sq: Seq[B]): mutable.Map[B, Int] = {
    val occ = new mutable.HashMap[B, Int] { override def default(k: B) = 0 }
    for (y <- sq) occ(y) += 1
    occ
  }

  /** 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 = {
    val b = newBuilder
    val seen = mutable.HashSet[A]()
    for (x <- this) {
      if (!seen(x)) {
        b += x
        seen += x
      }
    }
    b.result()
  }

  def patch[B >: A, That](from: Int, patch: GenSeq[B], replaced: Int)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
    val b = bf(repr)
    var i = 0
    val it = this.iterator
    while (i < from && it.hasNext) {
      b += it.next()
      i += 1
    }
    b ++= patch.seq
    i = replaced
    while (i > 0 && it.hasNext) {
      it.next()
      i -= 1
    }
    while (it.hasNext) b += it.next()
    b.result()
  }

  def updated[B >: A, That](index: Int, elem: B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
    if (index < 0) throw new IndexOutOfBoundsException(index.toString)
    val b = bf(repr)
    var i = 0
    val it = this.iterator
    while (i < index && it.hasNext) {
      b += it.next()
      i += 1
    }
    if (!it.hasNext) throw new IndexOutOfBoundsException(index.toString)
    b += elem
    it.next()
    while (it.hasNext) b += it.next()
    b.result()
  }

  def +:[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
    val b = bf(repr)
    b += elem
    b ++= thisCollection
    b.result()
  }

  def :+[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
    val b = bf(repr)
    b ++= thisCollection
    b += elem
    b.result()
  }

  def padTo[B >: A, That](len: Int, elem: B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
    val b = bf(repr)
    val L = length
    b.sizeHint(math.max(L, len))
    var diff = len - L
    b ++= thisCollection
    while (diff > 0) {
      b += elem
      diff -= 1
    }
    b.result()
  }

  def corresponds[B](that: GenSeq[B])(p: (A,B) => Boolean): Boolean = {
    val i = this.iterator
    val j = that.iterator
    while (i.hasNext && j.hasNext)
      if (!p(i.next(), j.next()))
        return false

    !i.hasNext && !j.hasNext
  }

  /** Sorts this $coll according to a comparison function.
   *  $willNotTerminateInf
   *
   *  The sort is stable. That is, elements that are equal (as determined by
   *  `lt`) appear in the same order in the sorted sequence as in the original.
   *
   *  @param  lt  the comparison function which tests whether
   *              its first argument precedes its second argument in
   *              the desired ordering.
   *  @return     a $coll consisting of the elements of this $coll
   *              sorted according to the comparison function `lt`.
   *  @example {{{
   *    List("Steve", "Tom", "John", "Bob").sortWith(_.compareTo(_) < 0) =
   *    List("Bob", "John", "Steve", "Tom")
   *  }}}
   */
  def sortWith(lt: (A, A) => Boolean): Repr = sorted(Ordering fromLessThan lt)

  /** Sorts this $Coll according to the Ordering which results from transforming
   *  an implicitly given Ordering with a transformation function.
   *  @see [[scala.math.Ordering]]
   *  $willNotTerminateInf
   *  @param   f the transformation function mapping elements
   *           to some other domain `B`.
   *  @param   ord the ordering assumed on domain `B`.
   *  @tparam  B the target type of the transformation `f`, and the type where
   *           the ordering `ord` is defined.
   *  @return  a $coll consisting of the elements of this $coll
   *           sorted according to the ordering where `x < y` if
   *           `ord.lt(f(x), f(y))`.
   *
   *  @example {{{
   *    val words = "The quick brown fox jumped over the lazy dog".split(' ')
   *    // this works because scala.Ordering will implicitly provide an Ordering[Tuple2[Int, Char]]
   *    words.sortBy(x => (x.length, x.head))
   *    res0: Array[String] = Array(The, dog, fox, the, lazy, over, brown, quick, jumped)
   *  }}}
   */
  def sortBy[B](f: A => B)(implicit ord: Ordering[B]): Repr = sorted(ord on f)

  /** Sorts this $coll according to an Ordering.
   *
   *  The sort is stable. That is, elements that are equal (as determined by
   *  `lt`) appear in the same order in the sorted sequence as in the original.
   *
   *  @see [[scala.math.Ordering]]
   *
   *  @param  ord the ordering to be used to compare elements.
   *  @return     a $coll consisting of the elements of this $coll
   *              sorted according to the ordering `ord`.
   */
  def sorted[B >: A](implicit ord: Ordering[B]): Repr = {
    val len = this.length
    val b = newBuilder
    if (len == 1) b ++= this
    else if (len > 1) {
      b.sizeHint(len)
      val arr = new Array[AnyRef](len)  // Previously used ArraySeq for more compact but slower code
      var i = 0
      for (x <- this) {
        arr(i) = x.asInstanceOf[AnyRef]
        i += 1
      }
      java.util.Arrays.sort(arr, ord.asInstanceOf[Ordering[Object]])
      i = 0
      while (i < arr.length) {
        b += arr(i).asInstanceOf[A]
        i += 1
      }
    }
    b.result()
  }

  /** Converts this $coll to a sequence.
   *  $willNotTerminateInf
   *
   *  A new collection will not be built; in particular, lazy sequences will stay lazy.
   */
  override def toSeq: Seq[A] = thisCollection

  /** Produces the range of all indices of this sequence.
   *
   *  @return  a `Range` value from `0` to one less than the length of this $coll.
   */
  def indices: Range = 0 until length

  override def view = new SeqView[A, Repr] {
    protected lazy val underlying = self.repr
    override def iterator = self.iterator
    override def length = self.length
    override def apply(idx: Int) = self.apply(idx)
  }

  override def view(from: Int, until: Int) = view.slice(from, until)

  /* Need to override string, so that it's not the Function1's string that gets mixed in.
   */
  override def toString = super[IterableLike].toString
}

/** The companion object for trait `SeqLike`.
 */
object SeqLike {
  // KMP search utilities

  /** Make sure a target sequence has fast, correctly-ordered indexing for KMP.
   *
   *  @author Rex Kerr
   *  @since  2.10
   *  @param  W    The target sequence
   *  @param  n0   The first element in the target sequence that we should use
   *  @param  n1   The far end of the target sequence that we should use (exclusive)
   *  @return Target packed in an IndexedSeq (taken from iterator unless W already is an IndexedSeq)
   */
  private def kmpOptimizeWord[B](W: Seq[B], n0: Int, n1: Int, forward: Boolean) = W match {
    case iso: IndexedSeq[_] =>
      // Already optimized for indexing--use original (or custom view of original)
      if (forward && n0==0 && n1==W.length) iso.asInstanceOf[IndexedSeq[B]]
      else if (forward) new AbstractSeq[B] with IndexedSeq[B] {
        val length = n1 - n0
        def apply(x: Int) = iso(n0 + x).asInstanceOf[B]
      }
      else new AbstractSeq[B] with IndexedSeq[B] {
        def length = n1 - n0
        def apply(x: Int) = iso(n1 - 1 - x).asInstanceOf[B]
      }
    case _ =>
      // W is probably bad at indexing.  Pack in array (in correct orientation)
      // Would be marginally faster to special-case each direction
      new AbstractSeq[B] with IndexedSeq[B] {
        private[this] val Warr = new Array[AnyRef](n1-n0)
        private[this] val delta = if (forward) 1 else -1
        private[this] val done = if (forward) n1-n0 else -1
        val wit = W.iterator.drop(n0)
        var i = if (forward) 0 else (n1-n0-1)
        while (i != done) {
          Warr(i) = wit.next().asInstanceOf[AnyRef]
          i += delta
        }

        val length = n1 - n0
        def apply(x: Int) = Warr(x).asInstanceOf[B]
      }
  }

 /** Make a jump table for KMP search.
   *
   *  @author paulp, Rex Kerr
   *  @since  2.10
   *  @param  Wopt The target sequence, as at least an IndexedSeq
   *  @param  wlen Just in case we're only IndexedSeq and not IndexedSeqOptimized
   *  @return KMP jump table for target sequence
   */
 private def kmpJumpTable[B](Wopt: IndexedSeq[B], wlen: Int) = {
    val arr = new Array[Int](wlen)
    var pos = 2
    var cnd = 0
    arr(0) = -1
    arr(1) = 0
    while (pos < wlen) {
      if (Wopt(pos-1) == Wopt(cnd)) {
        arr(pos) = cnd + 1
        pos += 1
        cnd += 1
      }
      else if (cnd > 0) {
        cnd = arr(cnd)
      }
      else {
        arr(pos) = 0
        pos += 1
      }
    }
    arr
  }

 /**  A KMP implementation, based on the undoubtedly reliable wikipedia entry.
   *  Note: I made this private to keep it from entering the API.  That can be reviewed.
   *
   *  @author paulp, Rex Kerr
   *  @since  2.10
   *  @param  S       Sequence that may contain target
   *  @param  m0      First index of S to consider
   *  @param  m1      Last index of S to consider (exclusive)
   *  @param  W       Target sequence
   *  @param  n0      First index of W to match
   *  @param  n1      Last index of W to match (exclusive)
   *  @param  forward Direction of search (from beginning==true, from end==false)
   *  @return Index of start of sequence if found, -1 if not (relative to beginning of S, not m0).
   */
  private def kmpSearch[B](S: Seq[B], m0: Int, m1: Int, W: Seq[B], n0: Int, n1: Int, forward: Boolean): Int = {
    // Check for redundant case when target has single valid element
    def clipR(x: Int, y: Int) = if (x < y) x else -1
    def clipL(x: Int, y: Int) = if (x > y) x else -1

    if (n1 == n0+1) {
      if (forward)
        clipR(S.indexOf(W(n0), m0), m1)
      else
        clipL(S.lastIndexOf(W(n0), m1-1), m0-1)
    }

    // Check for redundant case when both sequences are same size
    else if (m1-m0 == n1-n0) {
      // Accepting a little slowness for the uncommon case.
      if (S.view.slice(m0, m1) == W.view.slice(n0, n1)) m0
      else -1
    }
    // Now we know we actually need KMP search, so do it
    else S match {
      case xs: IndexedSeq[_] =>
        // We can index into S directly; it should be adequately fast
        val Wopt = kmpOptimizeWord(W, n0, n1, forward)
        val T = kmpJumpTable(Wopt, n1-n0)
        var i, m = 0
        val zero = if (forward) m0 else m1-1
        val delta = if (forward) 1 else -1
        while (i+m < m1-m0) {
          if (Wopt(i) == S(zero+delta*(i+m))) {
            i += 1
            if (i == n1-n0) return (if (forward) m+m0 else m1-m-i)
          }
          else {
            val ti = T(i)
            m += i - ti
            if (i > 0) i = ti
          }
        }
        -1
      case _ =>
        // We had better not index into S directly!
        val iter = S.iterator.drop(m0)
        val Wopt = kmpOptimizeWord(W, n0, n1, forward = true)
        val T = kmpJumpTable(Wopt, n1-n0)
        val cache = new Array[AnyRef](n1-n0)  // Ring buffer--need a quick way to do a look-behind
        var largest = 0
        var i, m = 0
        var answer = -1
        while (m+m0+n1-n0 <= m1) {
          while (i+m >= largest) {
            cache(largest%(n1-n0)) = iter.next().asInstanceOf[AnyRef]
            largest += 1
          }
          if (Wopt(i) == cache((i+m)%(n1-n0))) {
            i += 1
            if (i == n1-n0) {
              if (forward) return m+m0
              else {
                i -= 1
                answer = m+m0
                val ti = T(i)
                m += i - ti
                if (i > 0) i = ti
              }
            }
          }
          else {
            val ti = T(i)
            m += i - ti
            if (i > 0) i = ti
          }
        }
        answer
    }
  }

  /** Finds a particular index at which one sequence occurs in another sequence.
   *  Both the source sequence and the target sequence are expressed in terms
   *  other sequences S' and T' with offset and length parameters.  This
   *  function is designed to wrap the KMP machinery in a sufficiently general
   *  way that all library sequence searches can use it.  It is unlikely you
   *  have cause to call it directly: prefer functions such as StringBuilder#indexOf
   *  and Seq#lastIndexOf.
   *
   *  @param  source        the sequence to search in
   *  @param  sourceOffset  the starting offset in source
   *  @param  sourceCount   the length beyond sourceOffset to search
   *  @param  target        the sequence being searched for
   *  @param  targetOffset  the starting offset in target
   *  @param  targetCount   the length beyond targetOffset which makes up the target string
   *  @param  fromIndex     the smallest index at which the target sequence may start
   *
   *  @return the applicable index in source where target exists, or -1 if not found
   */
  def indexOf[B](
    source: Seq[B], sourceOffset: Int, sourceCount: Int,
    target: Seq[B], targetOffset: Int, targetCount: Int,
    fromIndex: Int
  ): Int = {
    // Fiddle with variables to match previous behavior and use kmpSearch
    // Doing LOTS of max/min, both clearer and faster to use math._
    val slen        = source.length
    val clippedFrom = math.max(0, fromIndex)
    val s0          = math.min(slen, sourceOffset + clippedFrom)
    val s1          = math.min(slen, s0 + sourceCount)
    val tlen        = target.length
    val t0          = math.min(tlen, targetOffset)
    val t1          = math.min(tlen, t0 + targetCount)

    // Error checking
    if (clippedFrom > slen-sourceOffset) -1   // Cannot return an index in range
    else if (t1 - t0 < 1) s0                  // Empty, matches first available position
    else if (s1 - s0 < t1 - t0) -1            // Source is too short to find target
    else {
      // Nontrivial search
      val ans = kmpSearch(source, s0, s1, target, t0, t1, forward = true)
      if (ans < 0) ans else ans - math.min(slen, sourceOffset)
    }
  }

  /** Finds a particular index at which one sequence occurs in another sequence.
   *  Like `indexOf`, but finds the latest occurrence rather than earliest.
   *
   *  @see  [[scala.collection.SeqLike]], method `indexOf`
   */
  def lastIndexOf[B](
    source: Seq[B], sourceOffset: Int, sourceCount: Int,
    target: Seq[B], targetOffset: Int, targetCount: Int,
    fromIndex: Int
  ): Int = {
    // Fiddle with variables to match previous behavior and use kmpSearch
    // Doing LOTS of max/min, both clearer and faster to use math._
    val slen        = source.length
    val tlen        = target.length
    val s0          = math.min(slen, sourceOffset)
    val s1          = math.min(slen, s0 + sourceCount)
    val clippedFrom = math.min(s1 - s0, fromIndex)
    val t0          = math.min(tlen, targetOffset)
    val t1          = math.min(tlen, t0 + targetCount)
    val fixed_s1    = math.min(s1, s0 + clippedFrom + (t1 - t0) - 1)

    // Error checking
    if (clippedFrom < 0) -1                   // Cannot return an index in range
    else if (t1 - t0 < 1) s0+clippedFrom      // Empty, matches last available position
    else if (fixed_s1 - s0 < t1 - t0) -1      // Source is too short to find target
    else {
      // Nontrivial search
      val ans = kmpSearch(source, s0, fixed_s1, target, t0, t1, forward = false)
      if (ans < 0) ans else ans - s0
    }
  }
}