List

@SerialVersionUID(3L) sealed abstract class List[+A] extends AbstractSeq[A] with LinearSeq[A] with LinearSeqOps[A, [A] =>> List[A], List[A]] with StrictOptimizedLinearSeqOps[A, [A] =>> List[A], List[A]] with StrictOptimizedSeqOps[A, [A] =>> List[A], List[A]] with IterableFactoryDefaults[A, [A] =>> List[A]] with DefaultSerializable
A class for immutable linked lists representing ordered collections of elements of type A.
This class comes with two implementing case classes scala.Nil and scala.:: that implement the abstract members isEmpty, head and tail.
This class is optimal for last-in-first-out (LIFO), stack-like access patterns. If you need another access pattern, for example, random access or FIFO, consider using a collection more suited to this than List.

Performance

Time: List has O(1) prepend and head/tail access. Most other operations are O(n) on the number of elements in the list. This includes the index-based lookup of elements, length, append and reverse.
Space: List implements structural sharing of the tail list. This means that many operations are either zero- or constant-memory cost.
val mainList = List(3, 2, 1)
val with4 =    4 :: mainList  // re-uses mainList, costs one :: instance
val with42 =   42 :: mainList // also re-uses mainList, cost one :: instance
val shorter =  mainList.tail  // costs nothing as it uses the same 2::1::Nil instances as mainList
See also
"Scala's Collection Library overview" section on Lists for more information.
Note
The functional list is characterized by persistence and structural sharing, thus offering considerable performance and space consumption benefits in some scenarios if used correctly. However, note that objects having multiple references into the same functional list (that is, objects that rely on structural sharing), will be serialized and deserialized with multiple lists, one for each reference to it. I.e. structural sharing is lost after serialization/deserialization.
Example
// Make a list via the companion object factory
val days = List("Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday")
// Make a list element-by-element
val when = "AM" :: "PM" :: Nil
// Pattern match
days match {
  case firstDay :: otherDays =>
    println("The first day of the week is: " + firstDay)
  case Nil =>
    println("There don't seem to be any week days.")
}
Companion
object
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trait StrictOptimizedSeqOps[A, [A] =>> List[A], List[A]]
trait StrictOptimizedLinearSeqOps[A, [A] =>> List[A], List[A]]
trait StrictOptimizedSeqOps[A, [A] =>> List[A], List[A]]
trait StrictOptimizedIterableOps[A, [A] =>> List[A], List[A]]
trait LinearSeq[A]
trait LinearSeqOps[A, [A] =>> List[A], List[A]]
trait LinearSeq[A]
trait LinearSeqOps[A, [A] =>> List[A], List[A]]
class AbstractSeq[A]
trait Seq[A]
trait SeqOps[A, [A] =>> List[A], List[A]]
trait Iterable[A]
class AbstractSeq[A]
trait Seq[A]
trait Equals
trait SeqOps[A, [A] =>> List[A], List[A]]
trait Int => A
trait Iterable[A]
trait IterableFactoryDefaults[A, [A] =>> List[A]]
trait IterableOps[A, [A] =>> List[A], List[A]]
trait IterableOnceOps[A, [A] =>> List[A], List[A]]
class Object
trait Matchable
class Any
class ::[A]
object Nil

Value members

Methods

override def iterableFactory: SeqFactory[[A] =>> List[A]]
Definition Classes
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def ::[B >: A](elem: B): List[B]
Adds an element at the beginning of this list.
Value Params
elem
the element to prepend.
Returns
a list which contains x as first element and which continues with this list. Example:
1 :: List(2, 3) = List(2, 3).::(1) = List(1, 2, 3)
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def :::[B >: A](prefix: List[B]): List[B]
Adds the elements of a given list in front of this list.
Example:
List(1, 2) ::: List(3, 4) = List(3, 4).:::(List(1, 2)) = List(1, 2, 3, 4)
Value Params
prefix
The list elements to prepend.
Returns
a list resulting from the concatenation of the given list prefix and this list.
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def reverse_:::[B >: A](prefix: List[B]): List[B]
Adds the elements of a given list in reverse order in front of this list. xs reverse_::: ys is equivalent to xs.reverse ::: ys but is more efficient.
Value Params
prefix
the prefix to reverse and then prepend
Returns
the concatenation of the reversed prefix and the current list.
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final override def isEmpty: Boolean
Definition Classes
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override def prepended[B >: A](elem: B): List[B]
Definition Classes
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override def prependedAll[B >: A](prefix: IterableOnce[B]): List[B]
Definition Classes
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override def appendedAll[B >: A](suffix: IterableOnce[B]): List[B]
Definition Classes
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override def take(n: Int): List[A]
Definition Classes
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override def slice(from: Int, until: Int): List[A]
Example
// Given a list
val letters = List('a','b','c','d','e')
// `slice` returns all elements beginning at index `from` and afterwards,
// up until index `until` (excluding index `until`.)
letters.slice(1,3) // Returns List('b','c')
Definition Classes
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override def takeRight(n: Int): List[A]
override def splitAt(n: Int): (List[A], List[A])
Definition Classes
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override def updated[B >: A](index: Int, elem: B): List[B]
Definition Classes
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final override def map[B](f: A => B): List[B]
final override def collect[B](pf: PartialFunction[A, B]): List[B]
final override def flatMap[B](f: A => IterableOnce[B]): List[B]
final override def takeWhile(p: A => Boolean): List[A]
Definition Classes
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final override def span(p: A => Boolean): (List[A], List[A])
final override def foreach[U](f: A => U): Unit
Definition Classes
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final override def reverse: List[A]
Definition Classes
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final override def foldRight[B](z: B)(op: (A, B) => B): B
Definition Classes
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final override def length: Int
Definition Classes
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final override def lengthCompare(len: Int): Int
Definition Classes
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final override def forall(p: A => Boolean): Boolean
Definition Classes
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final override def exists(p: A => Boolean): Boolean
Definition Classes
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final override def contains[A1 >: A](elem: A1): Boolean
Definition Classes
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final override def find(p: A => Boolean): Option[A]
Definition Classes
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override def last: A
Definition Classes
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override def corresponds[B](that: Seq[B])(p: (A, B) => Boolean): Boolean
Definition Classes
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final def mapConserve[B >: A <: AnyRef](f: A => B): List[B]
Builds a new list by applying a function to all elements of this list. Like xs map f, but returns xs unchanged if function f maps all elements to themselves (as determined by eq).
Type Params
B
the element type of the returned collection.
Value Params
f
the function to apply to each element.
Returns
a list resulting from applying the given function f to each element of this list and collecting the results.
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override def filter(p: A => Boolean): List[A]
override def filterNot(p: A => Boolean): List[A]
override def partition(p: A => Boolean): (List[A], List[A])
final override def toList: List[A]
Definition Classes
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override def equals(o: Any): Boolean
Definition Classes
Seq -> Equals -> Any
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Inherited methods

def lastIndexOf[B >: A](elem: B, end: Int): Int
Finds index of last occurrence of some value in this sequence before or at a given end index.
Note: will not terminate for infinite-sized collections.
Type Params
B
the type of the element elem.
Value Params
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.
Inhertied from
SeqOps
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def reduceRightOption[B >: A](op: (A, B) => B): Option[B]
Optionally applies a binary operator to all elements of this 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.
Type Params
B
the result type of the binary operator.
Value Params
op
the binary operator.
Returns
an option value containing the result of reduceRight(op) if this collection is nonempty, None otherwise.
Inhertied from
IterableOnceOps
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def runWith[U](action: A => U): Int => Boolean
Composes this partial function with an action function which gets applied to results of this partial function. The action function is invoked only for its side effects; its result is ignored.
Note that expression pf.runWith(action)(x) is equivalent to
if(pf isDefinedAt x) { action(pf(x)); true } else false
except that runWith is implemented via applyOrElse and thus potentially more efficient. Using runWith avoids double evaluation of pattern matchers and guards for partial function literals.
Value Params
action
the action function
Returns
a function which maps arguments x to isDefinedAt(x). The resulting function runs action(this(x)) where this is defined.
See also
applyOrElse.
Inhertied from
PartialFunction
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@deprecated("Use foldLeft instead of /:", "2.13.0") @inline
final def /:[B](z: B)(op: (B, A) => B): B
Inhertied from
IterableOnceOps
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def collectFirst[B](pf: PartialFunction[A, B]): Option[B]
Finds the first element of the collection 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.
Value Params
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.
Example
Seq("a", 1, 5L).collectFirst({ case x: Int => x*10 }) = Some(10)
Inhertied from
IterableOnceOps
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def groupMap[K, B](key: A => K)(f: A => B): Map[K, List[B]]
Partitions this iterable collection into a map of iterable collections according to a discriminator function key. Each element in a group is transformed into a value of type B using the value function.
It is equivalent to groupBy(key).mapValues(_.map(f)), but more efficient.
case class User(name: String, age: Int)

def namesByAge(users: Seq[User]): Map[Int, Seq[String]] =
  users.groupMap(_.age)(_.name)
Note: Even when applied to a view or a lazy collection it will always force the elements.
Type Params
B
the type of values returned by the transformation function
K
the type of keys returned by the discriminator function
Value Params
f
the element transformation function
key
the discriminator function
Inhertied from
IterableOps
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override def intersect[B >: A](that: Seq[B]): List[A]
Definition Classes
Inhertied from
StrictOptimizedSeqOps
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@deprecated("Use `concat` instead", "2.13.0") @inline
final def union[B >: A](that: Seq[B]): List[B]
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.
Type Params
B
the element type of the returned sequence.
Value Params
that
the sequence to add.
Returns
a new collection which contains all elements of this sequence followed by all elements of that.
Inhertied from
SeqOps
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override def zip[B](that: IterableOnce[B]): List[(A, B)]
override def drop(n: Int): List[A]
Inhertied from
IterableOnceOps
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override def partitionMap[A1, A2](f: A => Either[A1, A2]): (List[A1], List[A2])
@deprecated("Use .to(LazyList) instead of .toStream", "2.13.0") @inline
final def toStream: Stream[A]
Inhertied from
IterableOnceOps
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def sum[B >: A](num: Numeric[B]): B
Sums up the elements of this collection.
Note: will not terminate for infinite-sized collections.
Type Params
B
the result type of the + operator.
Value Params
num
an implicit parameter defining a set of numeric operations which includes the + operator to be used in forming the sum.
Returns
the sum of all elements of this collection with respect to the + operator in num.
Inhertied from
IterableOnceOps
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@deprecatedOverriding("Override indexOfSlice(that, from) instead - indexOfSlice(that) calls indexOfSlice(that, 0)", "2.13.0")
def indexOfSlice[B >: A](that: Seq[B]): Int
Finds first index where this sequence contains a given sequence as a slice.
Note: may not terminate for infinite-sized collections.
Value Params
that
the sequence to test
Returns
the first index >= 0 such that the elements of this sequence starting at this index match the elements of sequence that, or -1 of no such subsequence exists.
Inhertied from
SeqOps
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def indexOfSlice[B >: A](that: Seq[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.
Value Params
from
the start index
that
the sequence to test
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.
Inhertied from
SeqOps
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def corresponds[B](that: IterableOnce[B])(p: (A, B) => Boolean): Boolean
Tests whether every element of this collection's iterator relates to the corresponding element of another collection by satisfying a test predicate.
Note: will not terminate for infinite-sized collections.
Type Params
B
the type of the elements of that
Value Params
p
the test predicate, which relates elements from both collections
that
the other collection
Returns
true if both collections have the same length and p(x, y) is true for all corresponding elements x of this iterator and y of that, otherwise false
Inhertied from
IterableOnceOps
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def scanRight[B](z: B)(op: (A, B) => B): List[B]
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.
Note: Even when applied to a view or a lazy collection it will always force the elements.
Example:
List(1, 2, 3, 4).scanRight(0)(_ + _) == List(10, 9, 7, 4, 0)
Type Params
B
the type of the elements in the resulting collection
Value Params
op
the binary operator applied to the intermediate result and the element
z
the initial value
Returns
collection with intermediate results
Inhertied from
IterableOps
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def fold[A1 >: A](z: A1)(op: (A1, A1) => A1): A1
Folds the elements of this collection using the specified associative binary operator. The default implementation in IterableOnce is equivalent to foldLeft but may be overridden for more efficient traversal orders.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
Note: will not terminate for infinite-sized collections.
Type Params
A1
a type parameter for the binary operator, a supertype of A.
Value Params
op
a binary operator that must be associative.
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).
Returns
the result of applying the fold operator op between all the elements and z, or z if this collection is empty.
Inhertied from
IterableOnceOps
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@deprecated("Iterable.seq always returns the iterable itself", "2.13.0")
def seq: List[A]
Inhertied from
Iterable
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def minByOption[B](f: A => B)(cmp: Ordering[B]): Option[A]
Finds the first element which yields the smallest value measured by function f.
Note: will not terminate for infinite-sized collections.
Type Params
B
The result type of the function f.
Value Params
cmp
An ordering to be used for comparing elements.
f
The measuring function.
Returns
an option value containing the first element of this collection with the smallest value measured by function f with respect to the ordering cmp.
Inhertied from
IterableOnceOps
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def distinct: List[A]
Selects all the elements of this sequence ignoring the duplicates.
Returns
a new sequence consisting of all the elements of this sequence without duplicates.
Inhertied from
SeqOps
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def toArray[B >: A](evidence$1: ClassTag[B]): Array[B]
Convert collection to array.
Implementation note: DO NOT call Array.from from this method.
Inhertied from
IterableOnceOps
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@deprecatedOverriding("Override indexWhere(p, from) instead - indexWhere(p) calls indexWhere(p, 0)", "2.13.0")
def indexWhere(p: A => Boolean): Int
Finds index of the first element satisfying some predicate.
Note: may not terminate for infinite-sized collections.
Value Params
p
the predicate used to test elements.
Returns
the index >= 0 of the first element of this sequence that satisfies the predicate p, or -1, if none exists.
Inhertied from
SeqOps
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override def indexWhere(p: A => Boolean, from: Int): Int
Definition Classes
Inhertied from
LinearSeqOps
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Iterates over the inits of this iterable collection. The first value will be this iterable collection and the final one will be an empty iterable collection, with the intervening values the results of successive applications of init.
Note: Even when applied to a view or a lazy collection it will always force the elements.
Returns
an iterator over all the inits of this iterable collection
Example
List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)
Inhertied from
IterableOps
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def unapply(a: Int): Option[A]
Tries to extract a B from an A in a pattern matching expression.
Inhertied from
PartialFunction
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def sliding(size: Int, step: Int): Iterator[List[A]]
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)
The returned iterator will be empty when called on an empty collection. The last element the iterator produces may be smaller than the window size when the original collection isn't exhausted by the window before it and its last element isn't skipped by the step before it.
Value Params
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 element (which may be the only element) will be smaller if there are fewer than size elements remaining to be grouped.
See also
Example
List(1, 2, 3, 4, 5).sliding(2, 2) = Iterator(List(1, 2), List(3, 4), List(5))
List(1, 2, 3, 4, 5, 6).sliding(2, 3) = Iterator(List(1, 2), List(4, 5))
Inhertied from
IterableOps
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def sliding(size: Int): Iterator[List[A]]
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)
An empty collection returns an empty iterator, and a non-empty collection containing fewer elements than the window size returns an iterator that will produce the original collection as its only element.
Value Params
size
the number of elements per group
Returns
An iterator producing iterable collections of size size, except for a non-empty collection with less than size elements, which returns an iterator that produces the source collection itself as its only element.
See also
Example
List().sliding(2) = empty iterator
List(1).sliding(2) = Iterator(List(1))
List(1, 2).sliding(2) = Iterator(List(1, 2))
List(1, 2, 3).sliding(2) = Iterator(List(1, 2), List(2, 3))
Inhertied from
IterableOps
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def tail: List[A]
The rest of the collection without its first element.
Inhertied from
IterableOps
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@deprecated("`aggregate` is not relevant for sequential collections. Use `foldLeft(z)(seqop)` instead.", "2.13.0")
def aggregate[B](z: => B)(seqop: (B, A) => B, combop: (B, B) => B): B
Inhertied from
IterableOnceOps
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def transpose[B](asIterable: A => Iterable[B]): List[List[B]]
Transposes this iterable collection of iterable collections into a iterable collection of iterable collections.
The resulting collection's type will be guided by the static type of iterable collection. For example:
val xs = List(
           Set(1, 2, 3),
           Set(4, 5, 6)).transpose
// xs == List(
//         List(1, 4),
//         List(2, 5),
//         List(3, 6))

val ys = Vector(
           List(1, 2, 3),
           List(4, 5, 6)).transpose
// ys == Vector(
//         Vector(1, 4),
//         Vector(2, 5),
//         Vector(3, 6))
Note: Even when applied to a view or a lazy collection it will always force the elements.
Type Params
B
the type of the elements of each iterable collection.
Value Params
asIterable
an implicit conversion which asserts that the element type of this iterable collection is an Iterable.
Returns
a two-dimensional iterable collection of iterable collections which has as nth row the nth column of this iterable collection.
Throws
IllegalArgumentException
IllegalArgumentException
Inhertied from
IterableOps
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override def foldLeft[B](z: B)(op: (B, A) => B): B
Definition Classes
Inhertied from
LinearSeqOps
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def withFilter(p: A => Boolean): WithFilter[A, [A] =>> List[A]]
Creates a non-strict filter of this iterable 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.
Value Params
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 iterable collection which satisfy the predicate p.
Inhertied from
IterableOps
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override def patch[B >: A](from: Int, other: IterableOnce[B], replaced: Int): List[B]
Definition Classes
Inhertied from
StrictOptimizedSeqOps
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Appends all elements of this collection to a string builder. The written text consists of the string representations (w.r.t. the method toString) of all elements of this collection 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
Value Params
b
the string builder to which elements are appended.
Returns
the string builder b to which elements were appended.
Inhertied from
IterableOnceOps
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Appends all elements of this collection 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 collection, 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
Value Params
b
the string builder to which elements are appended.
sep
the separator string.
Returns
the string builder b to which elements were appended.
Inhertied from
IterableOnceOps
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Appends all elements of this collection 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 collection 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)
Value Params
b
the string builder to which elements are appended.
end
the ending string.
sep
the separator string.
start
the starting string.
Returns
the string builder b to which elements were appended.
Inhertied from
IterableOnceOps
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def lift: Int => Option[A]
Turns this partial function into a plain function returning an Option result.
Returns
a function that takes an argument x to Some(this(x)) if this is defined for x, and to None otherwise.
See also
Function.unlift
Inhertied from
PartialFunction
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final override def size: Int
Definition Classes
Inhertied from
SeqOps
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@deprecated("Use toIterable instead", "2.13.0")
Converts this iterable collection to an unspecified Iterable. Will return the same collection if this instance is already Iterable.
Returns
An Iterable containing all elements of this iterable collection.
Inhertied from
IterableOps
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final override def toSeq: List[A]
Definition Classes
Inhertied from
Seq
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def sortWith(lt: (A, A) => Boolean): List[A]
Sorts this sequence according to a comparison function.
Note: will not terminate for infinite-sized collections.
Note: Even when applied to a view or a lazy collection it will always force the elements.
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.
Value Params
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")
Inhertied from
SeqOps
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def minBy[B](f: A => B)(cmp: Ordering[B]): A
Finds the first element which yields the smallest value measured by function f.
Note: will not terminate for infinite-sized collections.
Type Params
B
The result type of the function f.
Value Params
cmp
An ordering to be used for comparing elements.
f
The measuring function.
Returns
the first element of this collection with the smallest value measured by function f with respect to the ordering cmp.
Throws
UnsupportedOperationException
UnsupportedOperationException
Inhertied from
IterableOnceOps
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override def empty: List[A]
override def segmentLength(p: A => Boolean, from: Int): Int
Definition Classes
Inhertied from
LinearSeqOps
Source
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final def segmentLength(p: A => Boolean): Int
Computes the length of the longest segment that starts from the first element and whose elements all satisfy some predicate.
Note: may not terminate for infinite-sized collections.
Value Params
p
the predicate used to test elements.
Returns
the length of the longest segment of this sequence that starts from the first element such that every element of the segment satisfies the predicate p.
Inhertied from
SeqOps
Source
(source)
@deprecatedOverriding("nonEmpty is defined as !isEmpty; override isEmpty instead", "2.13.0")
Tests whether the collection is not empty.
Returns
true if the collection contains at least one element, false otherwise.
Inhertied from
IterableOnceOps
Source
(source)
final def :+[B >: A](elem: B): List[B]
Alias for appended
Note that :-ending operators are right associative (see example). A mnemonic for +: vs. :+ is: the COLon goes on the COLlection side.
Inhertied from
SeqOps
Source
(source)
@deprecatedOverriding("Override lastIndexWhere(p, end) instead - lastIndexWhere(p) calls lastIndexWhere(p, Int.MaxValue)", "2.13.0")
Finds index of last element satisfying some predicate.
Note: will not terminate for infinite-sized collections.
Value Params
p
the predicate used to test elements.
Returns
the index of the last element of this sequence that satisfies the predicate p, or -1, if none exists.
Inhertied from
SeqOps
Source
(source)
override def lastIndexWhere(p: A => Boolean, end: Int): Int
Definition Classes
Inhertied from
LinearSeqOps
Source
(source)
def endsWith[B >: A](that: Iterable[B]): Boolean
Tests whether this sequence ends with the given sequence.
Note: will not terminate for infinite-sized collections.
Value Params
that
the sequence to test
Returns
true if this sequence has that as a suffix, false otherwise.
Inhertied from
SeqOps
Source
(source)
@deprecated("Check .knownSize instead of .hasDefiniteSize for more actionable information (see scaladoc for details)", "2.13.0")
Tests whether this collection is known to have a finite size. All strict collections are known to have finite size. For a non-strict collection such as Stream, the predicate returns true if all elements have been computed. It returns false if the stream is not yet evaluated to the end. Non-empty Iterators usually return false even if they were created from a collection with a known finite size.
Note: many collection methods will not work on collections of infinite sizes. The typical failure mode is an infinite loop. These methods always attempt a traversal without checking first that hasDefiniteSize returns true. However, checking hasDefiniteSize can provide an assurance that size is well-defined and non-termination is not a concern.
Returns
true if this collection is known to have finite size, false otherwise.
See also
method knownSize for a more useful alternative
Inhertied from
IterableOnceOps
Source
(source)
Composes another partial function k with this partial function so that this partial function gets applied to results of k.
Note that calling isDefinedAt on the resulting partial function may apply the first partial function and execute its side effect. It is highly recommended to call applyOrElse instead of isDefinedAt / apply for efficiency.
Type Params
R
the parameter type of the transformation function.
Value Params
k
the transformation function
Returns
a partial function with the domain of other partial function narrowed by this partial function, which maps arguments x to this(k(x)).
Inhertied from
PartialFunction
Source
(source)
def compose[A](g: A => Int): A => A
Composes two instances of Function1 in a new Function1, with this function applied last.
Type Params
A
the type to which function g can be applied
Value Params
g
a function A => T1
Returns
a new function f such that f(x) == apply(g(x))
Inhertied from
Function1
Source
(source)
final override def sizeCompare(that: Iterable[]): Int
Definition Classes
Inhertied from
SeqOps
Source
(source)
final override def sizeCompare(otherSize: Int): Int
Definition Classes
Inhertied from
SeqOps
Source
(source)
override def toString(): String
Definition Classes
Seq -> Function1 -> Iterable -> Any
Inhertied from
Seq
Source
(source)
override def tapEach[U](f: A => U): List[A]
override def distinctBy[B](f: A => B): List[A]
def lazyZip[B](that: Iterable[B]): LazyZip2[A, B, List[A]]
Analogous to zip except that the elements in each collection are not consumed until a strict operation is invoked on the returned LazyZip2 decorator.
Calls to lazyZip can be chained to support higher arities (up to 4) without incurring the expense of constructing and deconstructing intermediary tuples.
val xs = List(1, 2, 3)
val res = (xs lazyZip xs lazyZip xs lazyZip xs).map((a, b, c, d) => a + b + c + d)
// res == List(4, 8, 12)
Type Params
B
the type of the second element in each eventual pair
Value Params
that
the iterable providing the second element of each eventual pair
Returns
a decorator LazyZip2 that allows strict operations to be performed on the lazily evaluated pairs or chained calls to lazyZip. Implicit conversion to Iterable[(A, B)] is also supported.
Inhertied from
Iterable
Source
(source)
protected def reversed: Iterable[A]
Inhertied from
IterableOnceOps
Source
(source)
def reduceRight[B >: A](op: (A, B) => B): B
Applies a binary operator to all elements of this 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.
Type Params
B
the result type of the binary operator.
Value Params
op
the binary operator.
Returns
the result of inserting op between consecutive elements of this collection, going right to left: op(x1, op(x2, ..., op(xn-1, xn)...)) where x1, ..., xn are the elements of this collection.
Throws
UnsupportedOperationException
UnsupportedOperationException
Inhertied from
IterableOnceOps
Source
(source)
@deprecated("Use .reverseIterator.map(f).to(...) instead of .reverseMap(f)", "2.13.0")
def reverseMap[B](f: A => B): List[B]
Inhertied from
SeqOps
Source
(source)
def min[B >: A](ord: Ordering[B]): A
Finds the smallest element.
Note: will not terminate for infinite-sized collections.
Type Params
B
The type over which the ordering is defined.
Value Params
ord
An ordering to be used for comparing elements.
Returns
the smallest element of this collection with respect to the ordering ord.
Throws
UnsupportedOperationException
UnsupportedOperationException
Inhertied from
IterableOnceOps
Source
(source)
@deprecated("Use `dest ++= coll` instead", "2.13.0") @inline
final def copyToBuffer[B >: A](dest: Buffer[B]): Unit
Inhertied from
IterableOnceOps
Source
(source)
Returns
The number of elements in this collection, if it can be cheaply computed, -1 otherwise. Cheaply usually means: Not requiring a collection traversal.
Inhertied from
IterableOnce
Source
(source)
Inhertied from
SeqOps
Source
(source)
override def isDefinedAt(x: Int): Boolean
Definition Classes
Inhertied from
LinearSeqOps
Source
(source)
def toMap[K, V](ev: A <:< (K, V)): Map[K, V]
Inhertied from
IterableOnceOps
Source
(source)
def maxByOption[B](f: A => B)(cmp: Ordering[B]): Option[A]
Finds the first element which yields the largest value measured by function f.
Note: will not terminate for infinite-sized collections.
Type Params
B
The result type of the function f.
Value Params
cmp
An ordering to be used for comparing elements.
f
The measuring function.
Returns
an option value containing the first element of this collection with the largest value measured by function f with respect to the ordering cmp.
Inhertied from
IterableOnceOps
Source
(source)
def groupBy[K](f: A => K): Map[K, List[A]]
Partitions this iterable collection into a map of iterable collections according to some discriminator function.
Note: Even when applied to a view or a lazy collection it will always force the elements.
Type Params
K
the type of keys returned by the discriminator function.
Value Params
f
the discriminator function.
Returns
A map from keys to iterable 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 iterable collection of those elements x for which f(x) equals k.
Inhertied from
IterableOps
Source
(source)
final def toIterable: List[A]
Inhertied from
Iterable
Source
(source)
@deprecated("Use .iterator instead of .toIterator", "2.13.0") @inline
final def toIterator: Iterator[A]
Inhertied from
IterableOnceOps
Source
(source)
@deprecated("Use iterableFactory instead", "2.13.0") @deprecatedOverriding("Use iterableFactory instead", "2.13.0") @inline
def companion: IterableFactory[[A] =>> List[A]]
Inhertied from
IterableOps
Source
(source)
def maxBy[B](f: A => B)(cmp: Ordering[B]): A
Finds the first element which yields the largest value measured by function f.
Note: will not terminate for infinite-sized collections.
Type Params
B
The result type of the function f.
Value Params
cmp
An ordering to be used for comparing elements.
f
The measuring function.
Returns
the first element of this collection with the largest value measured by function f with respect to the ordering cmp.
Throws
UnsupportedOperationException
UnsupportedOperationException
Inhertied from
IterableOnceOps
Source
(source)
Composes this partial function with another partial function that gets applied to results of this partial function.
Note that calling isDefinedAt on the resulting partial function may apply the first partial function and execute its side effect. It is highly recommended to call applyOrElse instead of isDefinedAt / apply for efficiency.
Type Params
C
the result type of the transformation function.
Value Params
k
the transformation function
Returns
a partial function with the domain of this partial function narrowed by other partial function, which maps arguments x to k(this(x)).
Inhertied from
PartialFunction
Source
(source)
override def andThen[C](k: A => C): PartialFunction[Int, C]
Composes this partial function with a transformation function that gets applied to results of this partial function.
If the runtime type of the function is a PartialFunction then the other andThen method is used (note its cautions).
Type Params
C
the result type of the transformation function.
Value Params
k
the transformation function
Returns
a partial function with the domain of this partial function, possibly narrowed by the specified function, which maps arguments x to k(this(x)).
Definition Classes
Inhertied from
PartialFunction
Source
(source)
override def scanLeft[B](z: B)(op: (B, A) => B): List[B]
override def unzip[A1, A2](asPair: A => (A1, A2)): (List[A1], List[A2])
def grouped(size: Int): Iterator[List[A]]
Partitions elements in fixed size iterable collections.
Value Params
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.
See also
Inhertied from
IterableOps
Source
(source)
def maxOption[B >: A](ord: Ordering[B]): Option[A]
Finds the largest element.
Note: will not terminate for infinite-sized collections.
Type Params
B
The type over which the ordering is defined.
Value Params
ord
An ordering to be used for comparing elements.
Returns
an option value containing the largest element of this collection with respect to the ordering ord.
Inhertied from
IterableOnceOps
Source
(source)
def product[B >: A](num: Numeric[B]): B
Multiplies up the elements of this collection.
Note: will not terminate for infinite-sized collections.
Type Params
B
the result type of the * operator.
Value Params
num
an implicit parameter defining a set of numeric operations which includes the * operator to be used in forming the product.
Returns
the product of all elements of this collection with respect to the * operator in num.
Inhertied from
IterableOnceOps
Source
(source)
def orElse[A1 <: Int, B1 >: A](that: PartialFunction[A1, B1]): PartialFunction[A1, B1]
Composes this partial function with a fallback partial function which gets applied where this partial function is not defined.
Type Params
A1
the argument type of the fallback function
B1
the result type of the fallback function
Value Params
that
the fallback function
Returns
a partial function which has as domain the union of the domains of this partial function and that. The resulting partial function takes x to this(x) where this is defined, and to that(x) where it is not.
Inhertied from
PartialFunction
Source
(source)
def containsSlice[B](that: Seq[B]): Boolean
Tests whether this sequence contains a given sequence as a slice.
Note: may not terminate for infinite-sized collections.
Value Params
that
the sequence to test
Returns
true if this sequence contains a slice with the same elements as that, otherwise false.
Inhertied from
SeqOps
Source
(source)
def to[C1](factory: Factory[A, C1]): C1
Given a collection factory factory, convert this collection to the appropriate representation for the current element type A. Example uses:
xs.to(List) xs.to(ArrayBuffer) xs.to(BitSet) // for xs: Iterable[Int]
Inhertied from
IterableOnceOps
Source
(source)
@deprecated("Use foldRight instead of :\\", "2.13.0") @inline
final def :\[B](z: B)(op: (A, B) => B): B
Inhertied from
IterableOnceOps
Source
(source)
override def padTo[B >: A](len: Int, elem: B): List[B]
Definition Classes
Inhertied from
StrictOptimizedSeqOps
Source
(source)
@throws(scala.throws.$lessinit$greater$default$1[scala.IndexOutOfBoundsException])
override def apply(n: Int): A
Definition Classes
Inhertied from
LinearSeqOps
Source
(source)
override def diff[B >: A](that: Seq[B]): List[A]
Definition Classes
Inhertied from
StrictOptimizedSeqOps
Source
(source)
def scan[B >: A](z: B)(op: (B, B) => B): List[B]
Computes a prefix scan of the elements of the collection.
Note: The neutral element z may be applied more than once.
Type Params
B
element type of the resulting collection
Value Params
op
the associative operator for the scan
z
neutral element for the operator op
Returns
a new iterable collection containing the prefix scan of the elements in this iterable collection
Inhertied from
IterableOps
Source
(source)
override def sameElements[B >: A](that: IterableOnce[B]): Boolean
Definition Classes
Inhertied from
LinearSeqOps
Source
(source)
override def headOption: Option[A]
Definition Classes
Inhertied from
LinearSeqOps
Source
(source)
final def ++[B >: A](suffix: IterableOnce[B]): List[B]
Alias for concat
Inhertied from
IterableOps
Source
(source)
override def lengthCompare(that: Iterable[]): Int
Definition Classes
Inhertied from
LinearSeqOps
Source
(source)
def copyToArray[B >: A](xs: Array[B], start: Int, len: Int): Int
Copy elements to an array, returning the number of elements written.
Fills the given array xs starting at index start with at most len elements of this collection.
Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached, or len elements have been copied.
Type Params
B
the type of the elements of the array.
Value Params
len
the maximal number of elements to copy.
start
the starting index of xs.
xs
the array to fill.
Returns
the number of elements written to the array
Note
Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
Inhertied from
IterableOnceOps
Source
(source)
@deprecatedOverriding("This should always forward to the 3-arg version of this method", since = "2.13.4")
def copyToArray[B >: A](xs: Array[B], start: Int): Int
Copy elements to an array, returning the number of elements written.
Fills the given array xs starting at index start with values of this collection.
Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached.
Type Params
B
the type of the elements of the array.
Value Params
start
the starting index of xs.
xs
the array to fill.
Returns
the number of elements written to the array
Note
Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
Inhertied from
IterableOnceOps
Source
(source)
@deprecatedOverriding("This should always forward to the 3-arg version of this method", since = "2.13.4")
def copyToArray[B >: A](xs: Array[B]): Int
Copy elements to an array, returning the number of elements written.
Fills the given array xs starting at index start with values of this collection.
Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached.
Type Params
B
the type of the elements of the array.
Value Params
xs
the array to fill.
Returns
the number of elements written to the array
Note
Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
Inhertied from
IterableOnceOps
Source
(source)
final def +:[B >: A](elem: B): List[B]
Alias for prepended.
Note that :-ending operators are right associative (see example). A mnemonic for +: vs. :+ is: the COLon goes on the COLlection side.
Inhertied from
SeqOps
Source
(source)
@deprecatedOverriding("Override lastIndexOfSlice(that, end) instead - lastIndexOfSlice(that) calls lastIndexOfSlice(that, Int.MaxValue)", "2.13.0")
def lastIndexOfSlice[B >: A](that: Seq[B]): Int
Finds last index where this sequence contains a given sequence as a slice.
Note: will not terminate for infinite-sized collections.
Value Params
that
the sequence to test
Returns
the last 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.
Inhertied from
SeqOps
Source
(source)
def lastIndexOfSlice[B >: A](that: Seq[B], end: Int): Int
Finds last index before or at a given end index where this sequence contains a given sequence as a slice.
Note: will not terminate for infinite-sized collections.
Value Params
end
the end index
that
the sequence to test
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.
Inhertied from
SeqOps
Source
(source)
def minOption[B >: A](ord: Ordering[B]): Option[A]
Finds the smallest element.
Note: will not terminate for infinite-sized collections.
Type Params
B
The type over which the ordering is defined.
Value Params
ord
An ordering to be used for comparing elements.
Returns
an option value containing the smallest element of this collection with respect to the ordering ord.
Inhertied from
IterableOnceOps
Source
(source)
final def mkString: String
Displays all elements of this collection in a string.
Delegates to addString, which can be overridden.
Returns
a string representation of this collection. In the resulting string the string representations (w.r.t. the method toString) of all elements of this collection follow each other without any separator string.
Inhertied from
IterableOnceOps
Source
(source)
final def mkString(sep: String): String
Displays all elements of this collection in a string using a separator string.
Delegates to addString, which can be overridden.
Value Params
sep
the separator string.
Returns
a string representation of this collection. In the resulting string the string representations (w.r.t. the method toString) of all elements of this collection are separated by the string sep.
Example
List(1, 2, 3).mkString("|") = "1|2|3"
Inhertied from
IterableOnceOps
Source
(source)
final def mkString(start: String, sep: String, end: String): String
Displays all elements of this collection in a string using start, end, and separator strings.
Delegates to addString, which can be overridden.
Value Params
end
the ending string.
sep
the separator string.
start
the starting string.
Returns
a string representation of this collection. The resulting string begins with the string start and ends with the string end. Inside, the string representations (w.r.t. the method toString) of all elements of this collection are separated by the string sep.
Example
List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"
Inhertied from
IterableOnceOps
Source
(source)
def stepper[S <: Stepper[]](shape: StepperShape[A, S]): S
Returns a scala.collection.Stepper for the elements of this collection.
The Stepper enables creating a Java stream to operate on the collection, see scala.jdk.StreamConverters. For collections holding primitive values, the Stepper can be used as an iterator which doesn't box the elements.
The implicit scala.collection.StepperShape parameter defines the resulting Stepper type according to the element type of this collection.
Note that this method is overridden in subclasses and the return type is refined to S with EfficientSplit, for example scala.collection.IndexedSeqOps.stepper. For Steppers marked with scala.collection.Stepper.EfficientSplit, the converters in scala.jdk.StreamConverters allow creating parallel streams, whereas bare Steppers can be converted only to sequential streams.
Inhertied from
IterableOnce
Source
(source)
final def :++[B >: A](suffix: IterableOnce[B]): List[B]
Alias for appendedAll
Inhertied from
SeqOps
Source
(source)
Produces the range of all indices of this sequence.
Note: Even when applied to a view or a lazy collection it will always force the elements.
Returns
a Range value from 0 to one less than the length of this sequence.
Inhertied from
SeqOps
Source
(source)
def reduceOption[B >: A](op: (B, B) => B): Option[B]
Reduces the elements of this collection, if any, using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
Type Params
B
A type parameter for the binary operator, a supertype of A.
Value Params
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.
Inhertied from
IterableOnceOps
Source
(source)
protected def fromSpecific(coll: IterableOnce[A]): List[A]
def groupMapReduce[K, B](key: A => K)(f: A => B)(reduce: (B, B) => B): Map[K, B]
Partitions this iterable collection into a map according to a discriminator function key. All the values that have the same discriminator are then transformed by the f function and then reduced into a single value with the reduce function.
It is equivalent to groupBy(key).mapValues(_.map(f).reduce(reduce)), but more efficient.
def occurrences[A](as: Seq[A]): Map[A, Int] =
  as.groupMapReduce(identity)(_ => 1)(_ + _)
Note: Even when applied to a view or a lazy collection it will always force the elements.
Inhertied from
IterableOps
Source
(source)
An iterator yielding elements in reversed order.
Note: will not terminate for infinite-sized collections.
Note: xs.reverseIterator is the same as xs.reverse.iterator but might be more efficient.
Returns
an iterator yielding the elements of this sequence in reversed order
Inhertied from
SeqOps
Source
(source)
def count(p: A => Boolean): Int
Counts the number of elements in the collection which satisfy a predicate.
Note: will not terminate for infinite-sized collections.
Value Params
p
the predicate used to test elements.
Returns
the number of elements satisfying the predicate p.
Inhertied from
IterableOnceOps
Source
(source)
def canEqual(that: Any): Boolean
Inhertied from
Seq
Source
(source)
final override def concat[B >: A](suffix: IterableOnce[B]): List[B]
Definition Classes
Inhertied from
SeqOps
Source
(source)
Definition Classes
Inhertied from
IterableOps
Source
(source)
Returns a value class containing operations for comparing the length of this sequence to a test value.
These operations are implemented in terms of lengthCompare(Int), and allow the following more readable usages:
this.lengthIs < len     // this.lengthCompare(len) < 0
this.lengthIs <= len    // this.lengthCompare(len) <= 0
this.lengthIs == len    // this.lengthCompare(len) == 0
this.lengthIs != len    // this.lengthCompare(len) != 0
this.lengthIs >= len    // this.lengthCompare(len) >= 0
this.lengthIs > len     // this.lengthCompare(len) > 0
Inhertied from
SeqOps
Source
(source)
def init: List[A]
The initial part of the collection without its last element.
Note: Even when applied to a view or a lazy collection it will always force the elements.
Inhertied from
IterableOps
Source
(source)
Returns a value class containing operations for comparing the size of this iterable collection to a test value.
These operations are implemented in terms of sizeCompare(Int), and allow the following more readable usages:
this.sizeIs < size     // this.sizeCompare(size) < 0
this.sizeIs <= size    // this.sizeCompare(size) <= 0
this.sizeIs == size    // this.sizeCompare(size) == 0
this.sizeIs != size    // this.sizeCompare(size) != 0
this.sizeIs >= size    // this.sizeCompare(size) >= 0
this.sizeIs > size     // this.sizeCompare(size) > 0
Inhertied from
IterableOps
Source
(source)
def sortBy[B](f: A => B)(ord: Ordering[B]): List[A]
Sorts this sequence according to the Ordering which results from transforming an implicitly given Ordering with a transformation function.
Note: will not terminate for infinite-sized collections.
Note: Even when applied to a view or a lazy collection it will always force the elements.
The sort is stable. That is, elements that are equal (as determined by ord.compare) appear in the same order in the sorted sequence as in the original.
Type Params
B
the target type of the transformation f, and the type where the ordering ord is defined.
Value Params
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
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)
Inhertied from
SeqOps
Source
(source)
@deprecated("Use segmentLength instead of prefixLength", "2.13.0") @inline
final 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.
Value Params
p
the predicate used to test elements.
Returns
the length of the longest prefix of this sequence such that every element of the segment satisfies the predicate p.
Inhertied from
SeqOps
Source
(source)
def reduceLeft[B >: A](op: (B, A) => B): B
Applies a binary operator to all elements of this collection, 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.
Type Params
B
the result type of the binary operator.
Value Params
op
the binary operator.
Returns
the result of inserting op between consecutive elements of this collection, going left to right: op( op( ... op(x1, x2) ..., xn-1), xn) where x1, ..., xn are the elements of this collection.
Throws
UnsupportedOperationException
UnsupportedOperationException
Inhertied from
IterableOnceOps
Source
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def startsWith[B >: A](that: IterableOnce[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.
Value Params
offset
the index where the sequence is searched.
that
the sequence to test
Returns
true if the sequence that is contained in this sequence at index offset, otherwise false.
Inhertied from
SeqOps
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@deprecated("Use coll instead of repr in a collection implementation, use the collection value itself from the outside", "2.13.0")
final def repr: List[A]
Inhertied from
IterableOps
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Iterates over distinct permutations.
Note: Even when applied to a view or a lazy collection it will always force the elements.
Returns
An Iterator which traverses the distinct permutations of this sequence.
Example
"abb".permutations = Iterator(abb, bab, bba)
Inhertied from
SeqOps
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override def hashCode(): Int
Definition Classes
Seq -> Any
Inhertied from
Seq
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def toSet[B >: A]: Set[B]
Inhertied from
IterableOnceOps
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protected def newSpecificBuilder: Builder[A, List[A]]
def applyOrElse[A1 <: Int, B1 >: A](x: A1, default: A1 => B1): B1
Applies this partial function to the given argument when it is contained in the function domain. Applies fallback function where this partial function is not defined.
Note that expression pf.applyOrElse(x, default) is equivalent to
if(pf isDefinedAt x) pf(x) else default(x)
except that applyOrElse method can be implemented more efficiently. For all partial function literals the compiler generates an applyOrElse implementation which avoids double evaluation of pattern matchers and guards. This makes applyOrElse the basis for the efficient implementation for many operations and scenarios, such as:
- combining partial functions into orElse/andThen chains does not lead to excessive apply/isDefinedAt evaluation - lift and unlift do not evaluate source functions twice on each invocation - runWith allows efficient imperative-style combining of partial functions with conditionally applied actions
For non-literal partial function classes with nontrivial isDefinedAt method it is recommended to override applyOrElse with custom implementation that avoids double isDefinedAt evaluation. This may result in better performance and more predictable behavior w.r.t. side effects.
Value Params
default
the fallback function
x
the function argument
Returns
the result of this function or fallback function application.
Inhertied from
PartialFunction
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final def toBuffer[B >: A]: Buffer[B]
Inhertied from
IterableOnceOps
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@deprecatedOverriding("Override indexOf(elem, from) instead - indexOf(elem) calls indexOf(elem, 0)", "2.13.0")
def indexOf[B >: A](elem: B): Int
Finds index of first occurrence of some value in this sequence.
Type Params
B
the type of the element elem.
Value Params
elem
the element value to search for.
Returns
the index >= 0 of the first element of this sequence that is equal (as determined by ==) to elem, or -1, if none exists.
Inhertied from
SeqOps
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def indexOf[B >: A](elem: B, from: Int): Int
Finds index of first occurrence of some value in this sequence after or at some start index.
Type Params
B
the type of the element elem.
Value Params
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.
Inhertied from
SeqOps
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override def findLast(p: A => Boolean): Option[A]
Definition Classes
Inhertied from
LinearSeqOps
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override def dropRight(n: Int): List[A]
The rest of the collection without its n last elements. For linear, immutable collections this should avoid making a copy.
Note: Even when applied to a view or a lazy collection it will always force the elements.
Definition Classes
Inhertied from
StrictOptimizedIterableOps
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override def sorted[B >: A](ord: Ordering[B]): List[A]
Definition Classes
Inhertied from
StrictOptimizedSeqOps
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override def unzip3[A1, A2, A3](asTriple: A => (A1, A2, A3)): (List[A1], List[A2], List[A3])
def zipAll[A1 >: A, B](that: Iterable[B], thisElem: A1, thatElem: B): List[(A1, B)]
Returns a iterable collection formed from this iterable collection 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.
Value Params
that
the iterable providing the second half of each result pair
thatElem
the element to be used to fill up the result if that is shorter than this iterable collection.
thisElem
the element to be used to fill up the result if this iterable collection is shorter than that.
Returns
a new collection of type That containing pairs consisting of corresponding elements of this iterable collection and that. The length of the returned collection is the maximum of the lengths of this iterable collection and that. If this iterable collection is shorter than that, thisElem values are used to pad the result. If that is shorter than this iterable collection, thatElem values are used to pad the result.
Inhertied from
IterableOps
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override def appended[B >: A](elem: B): List[B]
Definition Classes
Inhertied from
StrictOptimizedSeqOps
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Returns an extractor object with a unapplySeq method, which extracts each element of a sequence data.
Example
val firstChar: String => Option[Char] = _.headOption
Seq("foo", "bar", "baz") match {
  case firstChar.unlift.elementWise(c0, c1, c2) =>
    println(s"$c0, $c1, $c2") // Output: f, b, b
}
Inhertied from
PartialFunction
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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.
Note: Even when applied to a view or a lazy collection it will always force the elements.
Returns
An Iterator which traverses the possible n-element combinations of this sequence.
Example
"abbbc".combinations(2) = Iterator(ab, ac, bb, bc)
Inhertied from
SeqOps
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def max[B >: A](ord: Ordering[B]): A
Finds the largest element.
Note: will not terminate for infinite-sized collections.
Type Params
B
The type over which the ordering is defined.
Value Params
ord
An ordering to be used for comparing elements.
Returns
the largest element of this collection with respect to the ordering ord.
Throws
UnsupportedOperationException
UnsupportedOperationException
Inhertied from
IterableOnceOps
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override def flatten[B](toIterableOnce: A => IterableOnce[B]): List[B]
final override def ++:[B >: A](prefix: IterableOnce[B]): List[B]
Alias for prependedAll
Definition Classes
Inhertied from
SeqOps
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@deprecated("Use .view.slice(from, until) instead of .view(from, until)", "2.13.0")
def view(from: Int, until: Int): View[A]
A view over a slice of the elements of this collection.
Inhertied from
IterableOps
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override def view: SeqView[A]
Definition Classes
Inhertied from
SeqOps
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def reduceLeftOption[B >: A](op: (B, A) => B): Option[B]
Optionally applies a binary operator to all elements of this collection, 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.
Type Params
B
the result type of the binary operator.
Value Params
op
the binary operator.
Returns
an option value containing the result of reduceLeft(op) if this collection is nonempty, None otherwise.
Inhertied from
IterableOnceOps
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override def tails: Iterator[List[A]]
Definition Classes
Inhertied from
LinearSeqOps
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def reduce[B >: A](op: (B, B) => B): B
Reduces the elements of this collection using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
Type Params
B
A type parameter for the binary operator, a supertype of A.
Value Params
op
A binary operator that must be associative.
Returns
The result of applying reduce operator op between all the elements if the collection is nonempty.
Throws
UnsupportedOperationException
UnsupportedOperationException
Inhertied from
IterableOnceOps
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Optionally selects the last element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
Returns
the last element of this iterable collection$ if it is nonempty, None if it is empty.
Inhertied from
IterableOps
Source
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