TraversableOnce

Companion object TraversableOnce

trait TraversableOnce[+A] extends GenTraversableOnce[A]

A template trait for collections which can be traversed either once only or one or more times.

This trait exists primarily to eliminate code duplication between Iterator and Traversable, and thus implements some of the common methods that can be implemented solely in terms of foreach without access to a Builder. It also includes a number of abstract methods whose implementations are provided by Iterator, Traversable, etc. It contains implementations common to Iterators and Traversables, such as folds, conversions, and other operations which traverse some or all of the elements and return a derived value. Directly subclassing TraversableOnce is not recommended - instead, consider declaring an Iterator with a next and hasNext method or creating an Iterator with one of the methods on the Iterator object. Consider declaring a subclass of Traversable instead if the elements can be traversed repeatedly.

Self Type: TraversableOnce[A]
Source: TraversableOnce.scala
Since: 2.8

Linear Supertypes

GenTraversableOnce[A], Any

Known Subclasses

ValueSet, AbstractIterable, AbstractIterator, AbstractMap, AbstractSeq, AbstractSet, AbstractTraversable, BitSet, BitSetLike, BufferedIterator, DefaultMap, IndexedSeq, IndexedSeqLike, Elements, IndexedSeqOptimized, Iterable, IterableLike, IterableView, IterableViewLike, Appended, DroppedWhile, EmptyView, Filtered, FlatMapped, Forced, Mapped, Prepended, Sliced, TakenWhile, Transformed, Zipped, ZippedAll, Iterator, GroupedIterator, LinearSeq, LinearSeqLike, LinearSeqOptimized, Map, WithDefault, MapLike, DefaultKeySet, DefaultValuesIterable, FilteredKeys, MappedValues, Seq, SeqLike, SeqView, SeqViewLike, Appended, DroppedWhile, EmptyView, Filtered, FlatMapped, Forced, Mapped, Patched, Prepended, Reversed, Sliced, TakenWhile, Transformed, Zipped, ZippedAll, Set, SetLike, SortedMap, SortedMapLike, DefaultKeySortedSet, SortedSet, SortedSetLike, Traversable, TraversableLike, TraversableView, TraversableViewLike, Appended, DroppedWhile, EmptyView, Filtered, FlatMapped, Forced, Mapped, Prepended, Sliced, TakenWhile, Transformed, Map, TrieMap, ::, AbstractMap, BitSet, BitSet1, BitSet2, BitSetN, DefaultMap, HashMap, HashMap1, HashTrieMap, HashSet, HashTrieSet, IndexedSeq, Impl, IntMap, Iterable, LinearSeq, List, ListMap, Node, ListSet, Node, LongMap, Map, Map1, Map2, Map3, Map4, WithDefault, MapLike, ImmutableDefaultKeySet, Nil, NumericRange, Exclusive, Inclusive, Queue, Range, Inclusive, Seq, Set, Set1, Set2, Set3, Set4, SortedMap, DefaultKeySortedSet, SortedSet, Stream, Cons, Empty, StreamIterator, StreamView, StreamViewLike, Appended, DroppedWhile, EmptyView, Filtered, FlatMapped, Forced, Mapped, Patched, Prepended, Reversed, Sliced, TakenWhile, Transformed, Zipped, ZippedAll, StringLike, StringOps, Traversable, TreeMap, TreeSet, Vector, VectorIterator, WrappedString, AbstractBuffer, AbstractIterable, AbstractMap, AbstractSeq, AbstractSet, AbstractSortedMap, AbstractSortedSet, AnyRefMap, ArrayBuffer, ArrayLike, ArrayOps, ofBoolean, ofByte, ofChar, ofDouble, ofFloat, ofInt, ofLong, ofRef, ofShort, ofUnit, ArraySeq, ArrayStack, BitSet, Buffer, BufferLike, HashMap, HashSet, History, IndexedSeq, IndexedSeqLike, IndexedSeqOptimized, IndexedSeqView, DroppedWhile, Filtered, Reversed, Sliced, TakenWhile, Transformed, Iterable, LinearSeq, LinkedHashMap, DefaultKeySet, FilteredKeys, MappedValues, LinkedHashSet, ListBuffer, ListMap, LongMap, Map, WithDefault, MapLike, MultiMap, MutableList, OpenHashMap, PriorityQueue, Queue, ResizableArray, RevertibleHistory, Seq, SeqLike, Set, SetLike, SortedMap, SortedSet, StringBuilder, Traversable, TreeMap, TreeSet, UnrolledBuffer, WrappedArray, ofBoolean, ofByte, ofChar, ofDouble, ofFloat, ofInt, ofLong, ofRef, ofShort, ofUnit, IterableSplitter, Appended, Mapped, Taken, Zipped, ZippedAll, Elements, PreciseSplitter, SeqSplitter, Appended, Mapped, Patched, Taken, Zipped, ZippedAll, Splitter, ParHashMapIterator, ParHashSetIterator, ParRangeIterator, ParVectorIterator, ParArrayIterator, ParFlatHashTableIterator, ParHashMapIterator, ParHashSetIterator, EntryIterator, BufferedSource, BufferedLineIterator, Source, LineIterator, SystemProperties, MatchIterator, IterableProxy, IterableProxyLike, MapProxy, MapProxyLike, SeqProxy, SeqProxyLike, SetProxy, SetProxyLike, TraversableProxy, TraversableProxyLike, IterableForwarder, SeqForwarder, TraversableForwarder, MapProxy, PagedSeq, SetProxy, Stack, BufferProxy, DefaultMapModel, DoubleLinkedList, DoubleLinkedListLike, ImmutableMapAdaptor, ImmutableSetAdaptor, LinkedList, LinkedListLike, MapProxy, ObservableBuffer, ObservableMap, ObservableSet, PriorityQueueProxy, QueueProxy, SetProxy, Stack, StackProxy, SynchronizedBuffer, SynchronizedMap, SynchronizedPriorityQueue, SynchronizedQueue, SynchronizedSet, SynchronizedStack, Script

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Inherited

TraversableOnce
GenTraversableOnce
Any

Implicitly

by MonadOps
by any2stringadd
by StringFormat
by Ensuring
by ArrowAssoc
by alternateImplicit

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Visibility

Public
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Abstract Value Members

abstract def exists(p: (A) ⇒ Boolean): Boolean
Tests whether a predicate holds for at least one element of this traversable or iterator.
Tests whether a predicate holds for at least one element of this traversable or iterator.
Note: may not terminate for infinite-sized collections.
p
the predicate used to test elements.
returns
true if the given predicate p is satisfied by at least one element of this traversable or iterator, otherwise false

Definition Classes
TraversableOnce → GenTraversableOnce
abstract def find(p: (A) ⇒ Boolean): Option[A]
Finds the first element of the traversable or iterator satisfying a predicate, if any.
Finds the first element of the traversable or iterator satisfying a predicate, if any.
Note: may not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
p
the predicate used to test elements.
returns
an option value containing the first element in the traversable or iterator that satisfies p, or None if none exists.

Definition Classes
TraversableOnce → GenTraversableOnce
abstract def forall(p: (A) ⇒ Boolean): Boolean
Tests whether a predicate holds for all elements of this traversable or iterator.
Tests whether a predicate holds for all elements of this traversable or iterator.
Note: may not terminate for infinite-sized collections.
p
the predicate used to test elements.
returns
true if this traversable or iterator is empty or the given predicate p holds for all elements of this traversable or iterator, otherwise false.

Definition Classes
TraversableOnce → GenTraversableOnce
abstract def getClass(): Class[_]
Returns the runtime class representation of the object.
Returns the runtime class representation of the object.
returns
a class object corresponding to the runtime type of the receiver.

Definition Classes
Any
abstract def hasDefiniteSize: Boolean
Tests whether this traversable or iterator is known to have a finite size.
Tests whether this traversable or iterator 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.

Definition Classes
TraversableOnce → GenTraversableOnce
abstract def isEmpty: Boolean
Tests whether the traversable or iterator is empty.
Tests whether the traversable or iterator is empty.
Note: Implementations in subclasses that are not repeatedly traversable must take care not to consume any elements when isEmpty is called.
returns
true if the traversable or iterator contains no elements, false otherwise.

Definition Classes
TraversableOnce → GenTraversableOnce
abstract def isTraversableAgain: Boolean
Tests whether this collection or iterator can be repeatedly traversed.
Tests whether this collection or iterator can be repeatedly traversed. Always true for Traversables and false for Iterators unless overridden.
returns
true if it is repeatedly traversable, false otherwise.

Definition Classes
GenTraversableOnce
abstract def seq: TraversableOnce[A]
A version of this collection with all of the operations implemented sequentially (i.e., in a single-threaded manner).
A version of this collection with all of the operations implemented sequentially (i.e., in a single-threaded manner).
This method returns a reference to this collection. In parallel collections, it is redefined to return a sequential implementation of this collection. In both cases, it has O(1) complexity.
returns
a sequential view of the collection.

Definition Classes
TraversableOnce → GenTraversableOnce
abstract def toIterator: Iterator[A]
Returns an Iterator over the elements in this collection or iterator.
Returns an Iterator over the elements in this collection or iterator. Will return the same Iterator if this instance is already an Iterator.
Note: will not terminate for infinite-sized collections.
returns
an Iterator containing all elements of this collection or iterator.

Definition Classes
GenTraversableOnce
abstract def toStream: Stream[A]
Converts this collection or iterator to a stream.
Converts this collection or iterator to a stream.
returns
a stream containing all elements of this collection or iterator.

Definition Classes
GenTraversableOnce
abstract def toTraversable: Traversable[A]
Converts this traversable or iterator to an unspecified Traversable.
Converts this traversable or iterator to an unspecified Traversable. Will return the same collection if this instance is already Traversable.
Note: will not terminate for infinite-sized collections.
returns
a Traversable containing all elements of this traversable or iterator.

Definition Classes
TraversableOnce → GenTraversableOnce

Concrete Value Members

final def !=(arg0: Any): Boolean
Test two objects for inequality.
Test two objects for inequality.
returns
true if !(this == that), false otherwise.

Definition Classes
Any
final def ##(): Int
Equivalent to x.hashCode except for boxed numeric types and null.
Equivalent to x.hashCode except for boxed numeric types and null. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For null returns a hashcode where null.hashCode throws a NullPointerException.
returns
a hash value consistent with ==

Definition Classes
Any
def +(other: String): String

Implicit
This member is added by an implicit conversion from TraversableOnce[A] to any2stringadd[TraversableOnce[A]] performed by method any2stringadd in scala.Predef.
Definition Classes
any2stringadd
def ->[B](y: B): (TraversableOnce[A], B)

Implicit
This member is added by an implicit conversion from TraversableOnce[A] to ArrowAssoc[TraversableOnce[A]] performed by method ArrowAssoc in scala.Predef.
Definition Classes
ArrowAssoc
Annotations
@inline()
final def ==(arg0: Any): Boolean
Test two objects for equality.
Test two objects for equality. The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).
returns
true if the receiver object is equivalent to the argument; false otherwise.

Definition Classes
Any
def addString(b: StringBuilder): StringBuilder
Appends all elements of this traversable or iterator to a string builder.
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.
def addString(b: StringBuilder, sep: String): StringBuilder
Appends all elements of this traversable or iterator to a string builder using a separator string.
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.
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.
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.
def aggregate[B](z: ⇒ B)(seqop: (B, A) ⇒ B, combop: (B, B) ⇒ B): B
Aggregates the results of applying an operator to subsequent elements.
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
final def asInstanceOf[T0]: T0
Cast the receiver object to be of type T0.
Cast the receiver object to be of type T0.
Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expression List(1).asInstanceOf[List[String]] will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.
returns
the receiver object.

Definition Classes
Any
Exceptions thrown
ClassCastException if the receiver object is not an instance of the erasure of type T0.
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.
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.
Example:
1. Seq("a", 1, 5L).collectFirst({ case x: Int => x*10 }) = Some(10)
def copyToArray(xs: Array[A]): Unit
[use case] Copies the elements of this traversable or iterator to an array.
[use case]
Copies the elements of this traversable or iterator to an array. Fills the given array xs with values of this traversable or iterator. Copying will stop once either the end of the current traversable or iterator 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
Full Signature
def copyToArray[B >: A](xs: Array[B]): Unit
def copyToArray(xs: Array[A], start: Int): Unit
[use case] Copies the elements of this traversable or iterator to an array.
[use case]
Copies the elements of this traversable or iterator to an array. Fills the given array xs with values of this traversable or iterator, beginning at index start. Copying will stop once either the end of the current traversable or iterator 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
Full Signature
def copyToArray[B >: A](xs: Array[B], start: Int): Unit
abstract def copyToArray(xs: Array[A], start: Int, len: Int): Unit
[use case] Copies the elements of this traversable or iterator to an array.
[use case]
Copies the elements of this traversable or iterator to an array. Fills the given array xs with at most len elements of this traversable or iterator, starting at position start. Copying will stop once either the end of the current traversable or iterator 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
TraversableOnce → GenTraversableOnce
Full Signature
abstract def copyToArray[B >: A](xs: Array[B], start: Int, len: Int): Unit
def copyToBuffer[B >: A](dest: Buffer[B]): Unit
Copies all elements of this traversable or iterator to a buffer.
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.
def count(p: (A) ⇒ Boolean): Int
Counts the number of elements in the traversable or iterator which satisfy a predicate.
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
def ensuring(cond: (TraversableOnce[A]) ⇒ Boolean, msg: ⇒ Any): TraversableOnce[A]

Implicit
This member is added by an implicit conversion from TraversableOnce[A] to Ensuring[TraversableOnce[A]] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring
def ensuring(cond: (TraversableOnce[A]) ⇒ Boolean): TraversableOnce[A]

Implicit
This member is added by an implicit conversion from TraversableOnce[A] to Ensuring[TraversableOnce[A]] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring
def ensuring(cond: Boolean, msg: ⇒ Any): TraversableOnce[A]

Implicit
This member is added by an implicit conversion from TraversableOnce[A] to Ensuring[TraversableOnce[A]] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring
def ensuring(cond: Boolean): TraversableOnce[A]

Implicit
This member is added by an implicit conversion from TraversableOnce[A] to Ensuring[TraversableOnce[A]] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring
def equals(arg0: Any): Boolean
Compares the receiver object (this) with the argument object (that) for equivalence.
Compares the receiver object (this) with the argument object (that) for equivalence.
Any implementation of this method should be an equivalence relation:
- It is reflexive: for any instance x of type Any, x.equals(x) should return true.
- It is symmetric: for any instances x and y of type Any, x.equals(y) should return true if and only if y.equals(x) returns true.
- It is transitive: for any instances x, y, and z of type Any if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
If you override this method, you should verify that your implementation remains an equivalence relation. Additionally, when overriding this method it is usually necessary to override hashCode to ensure that objects which are "equal" (o1.equals(o2) returns true) hash to the same scala.Int. (o1.hashCode.equals(o2.hashCode)).
returns
true if the receiver object is equivalent to the argument; false otherwise.

Definition Classes
Any
def filter(p: (A) ⇒ Boolean): TraversableOnce[A]

Implicit
This member is added by an implicit conversion from TraversableOnce[A] to MonadOps[A] performed by method MonadOps in scala.collection.TraversableOnce.
Definition Classes
MonadOps
def flatMap[B](f: (A) ⇒ GenTraversableOnce[B]): TraversableOnce[B]

Implicit
This member is added by an implicit conversion from TraversableOnce[A] to MonadOps[A] performed by method MonadOps in scala.collection.TraversableOnce.
Definition Classes
MonadOps
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.
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
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.
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, ..., x_n are the elements of this traversable or iterator. Returns z if this traversable or iterator is empty.
Definition Classes
TraversableOnce → GenTraversableOnce
def foldRight[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.
Applies a binary operator to all elements of this traversable or iterator and a start value, going right to left.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
B
the result type of the binary operator.
z
the start value.
op
the binary operator.
returns
the result of inserting op between consecutive elements of this 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, ..., x_n are the elements of this traversable or iterator. Returns z if this traversable or iterator is empty.
Definition Classes
TraversableOnce → GenTraversableOnce
abstract def foreach(f: (A) ⇒ Unit): Unit
[use case] Applies a function f to all elements of this traversable or iterator.
[use case]
Applies a function f to all elements of this traversable or iterator.
Note: this method underlies the implementation of most other bulk operations. It's important to implement this method in an efficient way.
f
the function that is applied for its side-effect to every element. The result of function f is discarded.

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
abstract def foreach[U](f: (A) ⇒ U): Unit
def hashCode(): Int
Calculate a hash code value for the object.
Calculate a hash code value for the object.
The default hashing algorithm is platform dependent.
Note that it is allowed for two objects to have identical hash codes (o1.hashCode.equals(o2.hashCode)) yet not be equal (o1.equals(o2) returns false). A degenerate implementation could always return 0. However, it is required that if two objects are equal (o1.equals(o2) returns true) that they have identical hash codes (o1.hashCode.equals(o2.hashCode)). Therefore, when overriding this method, be sure to verify that the behavior is consistent with the equals method.
returns
the hash code value for this object.

Definition Classes
Any
final def isInstanceOf[T0]: Boolean
Test whether the dynamic type of the receiver object is T0.
Test whether the dynamic type of the receiver object is T0.
Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression 1.isInstanceOf[String] will return false, while the expression List(1).isInstanceOf[List[String]] will return true. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.
returns
true if the receiver object is an instance of erasure of type T0; false otherwise.

Definition Classes
Any
def map[B](f: (A) ⇒ B): TraversableOnce[B]

Implicit
This member is added by an implicit conversion from TraversableOnce[A] to MonadOps[A] performed by method MonadOps in scala.collection.TraversableOnce.
Definition Classes
MonadOps
def max: A
[use case] Finds the largest element.
[use case]
Finds the largest element.
returns
the largest element of this traversable or iterator.

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def max[B >: A](implicit cmp: Ordering[B]): A

Exceptions thrown
UnsupportedOperationException if this traversable or iterator is empty.
def maxBy[B](f: (A) ⇒ B): A
[use case] Finds the first element which yields the largest value measured by function f.
[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 traversable or iterator with the largest value measured by function f.

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def maxBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A

Exceptions thrown
UnsupportedOperationException if this traversable or iterator is empty.
def min: A
[use case] Finds the smallest element.
[use case]
Finds the smallest element.
returns
the smallest element of this traversable or iterator

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def min[B >: A](implicit cmp: Ordering[B]): A

Exceptions thrown
UnsupportedOperationException if this traversable or iterator is empty.
def minBy[B](f: (A) ⇒ B): A
[use case] Finds the first element which yields the smallest value measured by function f.
[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 traversable or iterator with the smallest value measured by function f.

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def minBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A

Exceptions thrown
UnsupportedOperationException if this traversable or iterator is empty.
def mkString: String
Displays all elements of this traversable or iterator in a string.
Displays all elements of this traversable or iterator in a 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 follow each other without any separator string.

Definition Classes
TraversableOnce → GenTraversableOnce
def mkString(sep: String): String
Displays all elements of this traversable or iterator in a string using a separator 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:
1. List(1, 2, 3).mkString("|") = "1|2|3"
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.
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:
1. List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"
def nonEmpty: Boolean
Tests whether the traversable or iterator is not empty.
Tests whether the traversable or iterator is not empty.
returns
true if the traversable or iterator contains at least one element, false otherwise.

Definition Classes
TraversableOnce → GenTraversableOnce
def product: A
[use case] Multiplies up the elements of this collection.
[use case]
Multiplies up the elements of this collection.
returns
the product of all elements in this traversable or iterator of numbers of type Int. Instead of Int, any other type T with an implicit Numeric[T] implementation can be used as element type of the traversable or iterator and as result type of product. Examples of such types are: Long, Float, Double, BigInt.

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def product[B >: A](implicit num: Numeric[B]): B
def reduce[A1 >: A](op: (A1, A1) ⇒ A1): A1
Reduces the elements of this traversable or iterator using the specified associative binary operator.
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.
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.
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, ..., x_n are the elements of this traversable or iterator.
Exceptions thrown
UnsupportedOperationException if this traversable or iterator is empty.
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.
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
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.
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
def reduceRight[B >: A](op: (A, B) ⇒ B): B
Applies a binary operator to all elements of this traversable or iterator, going right to left.
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
the result of inserting op between consecutive elements of this traversable or iterator, going right to left:
```
op(x_1, op(x_2, ..., op(x_{n-1}, x_n)...))
```
where x₁, ..., x_n are the elements of this traversable or iterator.
Definition Classes
TraversableOnce → GenTraversableOnce
Exceptions thrown
UnsupportedOperationException if this traversable or iterator is empty.
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.
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
def reversed: List[A]

Attributes
protected[this]
def size: Int
The size of this traversable or iterator.
The size of this traversable or iterator.
Note: will not terminate for infinite-sized collections.
returns
the number of elements in this traversable or iterator.

Definition Classes
TraversableOnce → GenTraversableOnce
def sizeHintIfCheap: Int
The size of this collection or iterator, if it can be cheaply computed
The size of this collection or iterator, if it can be cheaply computed
returns
the number of elements in this collection or iterator, or -1 if the size cannot be determined cheaply

Attributes
protected[collection]
Definition Classes
GenTraversableOnce
def sum: A
[use case] Sums up the elements of this collection.
[use case]
Sums up the elements of this collection.
returns
the sum of all elements in this traversable or iterator of numbers of type Int. Instead of Int, any other type T with an implicit Numeric[T] implementation can be used as element type of the traversable or iterator and as result type of sum. Examples of such types are: Long, Float, Double, BigInt.

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def sum[B >: A](implicit num: Numeric[B]): B
def to[Col[_]]: Col[A]
[use case] Converts this traversable or iterator into another by copying all elements.
[use case]
Converts this traversable or iterator into another by copying all elements.
Note: will not terminate for infinite-sized collections.
Col
The collection type to build.
returns
a new collection containing all elements of this traversable or iterator.

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def to[Col[_]](implicit cbf: CanBuildFrom[Nothing, A, Col[A]]): Col[A]
def toArray: Array[A]
[use case] Converts this traversable or iterator to an array.
[use case]
Converts this traversable or iterator to an array.
Note: will not terminate for infinite-sized collections.
returns
an array containing all elements of this traversable or iterator. An ClassTag must be available for the element type of this traversable or iterator.

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def toArray[B >: A](implicit arg0: ClassTag[B]): Array[B]
def toBuffer[B >: A]: Buffer[B]
Uses the contents of this traversable or iterator to create a new mutable buffer.
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
def toIndexedSeq: immutable.IndexedSeq[A]
Converts this traversable or iterator to an indexed sequence.
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
def toIterable: Iterable[A]
Converts this traversable or iterator to an iterable collection.
Converts this traversable or iterator to an iterable collection. Note that the choice of target Iterable is lazy in this default implementation as this TraversableOnce may be lazy and unevaluated (i.e. it may be an iterator which is only traversable once).
Note: will not terminate for infinite-sized collections.
returns
an Iterable containing all elements of this traversable or iterator.

Definition Classes
TraversableOnce → GenTraversableOnce
def toList: List[A]
Converts this traversable or iterator to a list.
Converts this traversable or iterator to a list.
Note: will not terminate for infinite-sized collections.
returns
a list containing all elements of this traversable or iterator.

Definition Classes
TraversableOnce → GenTraversableOnce
def toMap[T, U]: Map[T, U]
[use case] Converts this traversable or iterator to a map.
[use case]
Converts this traversable or iterator 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 traversable or iterator.

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def toMap[T, U](implicit ev: <:<[A, (T, U)]): immutable.Map[T, U]
def toSeq: Seq[A]
Converts this traversable or iterator to a sequence.
Converts this traversable or iterator to a sequence. As with toIterable, it's lazy in this default implementation, as this TraversableOnce may be lazy and unevaluated.
Note: will not terminate for infinite-sized collections.
returns
a sequence containing all elements of this traversable or iterator.

Definition Classes
TraversableOnce → GenTraversableOnce
def toSet[B >: A]: immutable.Set[B]
Converts this traversable or iterator to a set.
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
def toString(): String
Returns a string representation of the object.
Returns a string representation of the object.
The default representation is platform dependent.
returns
a string representation of the object.

Definition Classes
Any
def toVector: Vector[A]
Converts this traversable or iterator to a Vector.
Converts this traversable or iterator to a Vector.
Note: will not terminate for infinite-sized collections.
returns
a vector containing all elements of this traversable or iterator.

Definition Classes
TraversableOnce → GenTraversableOnce
def withFilter(p: (A) ⇒ Boolean): Iterator[A]

Implicit
This member is added by an implicit conversion from TraversableOnce[A] to MonadOps[A] performed by method MonadOps in scala.collection.TraversableOnce.
Definition Classes
MonadOps
def →[B](y: B): (TraversableOnce[A], B)

Implicit
This member is added by an implicit conversion from TraversableOnce[A] to ArrowAssoc[TraversableOnce[A]] performed by method ArrowAssoc in scala.Predef.
Definition Classes
ArrowAssoc

Deprecated Value Members

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.
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, ..., x_n are the elements of this traversable or iterator.
Definition Classes
TraversableOnce → GenTraversableOnce
Annotations
@deprecated
Deprecated
(Since version 2.12.10) Use foldLeft instead of /:
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.
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, ..., x_n are the elements of this traversable or iterator.
Definition Classes
TraversableOnce → GenTraversableOnce
Annotations
@deprecated
Deprecated
(Since version 2.12.10) Use foldRight instead of :\
def formatted(fmtstr: String): String
Returns string formatted according to given format string.
Returns string formatted according to given format string. Format strings are as for String.format (@see java.lang.String.format).

Implicit
This member is added by an implicit conversion from TraversableOnce[A] to StringFormat[TraversableOnce[A]] performed by method StringFormat in scala.Predef.
Definition Classes
StringFormat
Annotations
@deprecated @inline()
Deprecated
(Since version 2.12.16) Use formatString.format(value) instead of value.formatted(formatString), or use the f"" string interpolator. In Java 15 and later, formatted resolves to the new method in String which has reversed parameters.

Packages

Package structure

Automatic imports

Guide

Using Collections

Creating Collections

Converting to and from Java Collections

TraversableOnce

Companion object TraversableOnce

trait TraversableOnce[+A] extends GenTraversableOnce[A]

Abstract Value Members

Concrete Value Members

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

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

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

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

def max[B >: A](implicit cmp: Ordering[B]): A

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

def min[B >: A](implicit cmp: Ordering[B]): A

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

def product[B >: A](implicit num: Numeric[B]): B

def sum[B >: A](implicit num: Numeric[B]): B

def to[Col[_]](implicit cbf: CanBuildFrom[Nothing, A, Col[A]]): Col[A]

def toArray[B >: A](implicit arg0: ClassTag[B]): Array[B]

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

Deprecated Value Members

Inherited from GenTraversableOnce[A]

Inherited from Any

Inherited by implicit conversion MonadOps from TraversableOnce[A] to MonadOps[A]

Inherited by implicit conversion any2stringadd from TraversableOnce[A] to any2stringadd[TraversableOnce[A]]

Inherited by implicit conversion StringFormat from TraversableOnce[A] to StringFormat[TraversableOnce[A]]

Inherited by implicit conversion Ensuring from TraversableOnce[A] to Ensuring[TraversableOnce[A]]

Inherited by implicit conversion ArrowAssoc from TraversableOnce[A] to ArrowAssoc[TraversableOnce[A]]

Inherited by implicit conversion alternateImplicit from TraversableOnce[A] to ForceImplicitAmbiguity

Ungrouped

Packages

Package structure

Automatic imports

Guide

Using Collections

Creating Collections

Converting to and from Java Collections

TraversableOnce 

Companion object TraversableOnce

trait TraversableOnce[+A] extends GenTraversableOnce[A]

Abstract Value Members

Concrete Value Members

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

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

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

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

def max[B >: A](implicit cmp: Ordering[B]): A

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

def min[B >: A](implicit cmp: Ordering[B]): A

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

def product[B >: A](implicit num: Numeric[B]): B

def sum[B >: A](implicit num: Numeric[B]): B

def to[Col[_]](implicit cbf: CanBuildFrom[Nothing, A, Col[A]]): Col[A]

def toArray[B >: A](implicit arg0: ClassTag[B]): Array[B]

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

Deprecated Value Members

Inherited from GenTraversableOnce[A]

Inherited from Any

Inherited by implicit conversion MonadOps from TraversableOnce[A] to MonadOps[A]

Inherited by implicit conversion any2stringadd from TraversableOnce[A] to any2stringadd[TraversableOnce[A]]

Inherited by implicit conversion StringFormat from TraversableOnce[A] to StringFormat[TraversableOnce[A]]

Inherited by implicit conversion Ensuring from TraversableOnce[A] to Ensuring[TraversableOnce[A]]

Inherited by implicit conversion ArrowAssoc from TraversableOnce[A] to ArrowAssoc[TraversableOnce[A]]

Inherited by implicit conversion alternateImplicit from TraversableOnce[A] to ForceImplicitAmbiguity

Ungrouped

TraversableOnce