Trait scala.collection.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

Known Subclasses

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.

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.

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.

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: 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. 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.

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. 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).

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. 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.

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. 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.

returns: true if !(this == that), false otherwise.

Definition Classes: Any

final def ##(): Int

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()

def /:[B](z: B)(op: (B, A) ⇒ B): B

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

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

Examples:

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

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

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

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

Note: will not terminate for infinite-sized collections.

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

B

the result type of the binary operator.

z

the start value.

op

the binary operator.

returns

the result of inserting op between consecutive elements of this traversable or iterator, going left to right with the start value z on the left:

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

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

Definition Classes: TraversableOnce → GenTraversableOnce

def :\[B](z: B)(op: (A, B) ⇒ B): B

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

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

Note: will not terminate for infinite-sized collections.

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

Examples:

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

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

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

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

B

the result type of the binary operator.

z

the start value

op

the binary operator

returns

the result of inserting op between consecutive elements of this traversable or iterator, going right to left with the start value z on the right:

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

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

Definition Classes: TraversableOnce → GenTraversableOnce

final def ==(arg0: Any): Boolean

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. 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. 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. 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.

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.

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.

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:

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. 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

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

[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

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

[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

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

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

Note: will not terminate for infinite-sized collections.

dest: The buffer to which elements are copied.

def count(p: (A) ⇒ Boolean): Int

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

p: the predicate used to test elements.
returns: the number of elements satisfying the predicate p.

Definition Classes: TraversableOnce → GenTraversableOnce

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.

Any implementation of this method should be an equivalence relation:

x

Any

x.equals(x)

true

x

y

Any

x.equals(y)

true

y.equals(x)

true

x

y

z

Any

x.equals(y)

true

y.equals(z)

true

x.equals(z)

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.

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.

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.

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.

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

def formatted(fmtstr: String): 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: @inline()

def hashCode(): Int

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.

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.

returns: the largest element of this traversable or iterator.

Definition Classes: TraversableOnce → GenTraversableOnce
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.

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
Exceptions thrown: UnsupportedOperationException if this traversable or iterator is empty.

def min: A

[use case]

Finds the smallest element.

returns: the smallest element of this traversable or iterator

Definition Classes: TraversableOnce → GenTraversableOnce
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.

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
Exceptions thrown: UnsupportedOperationException if this traversable or iterator is empty.

def mkString: 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.

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

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

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

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

Definition Classes: TraversableOnce → GenTraversableOnce

def nonEmpty: Boolean

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.

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

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

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

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

A1: A type parameter for the binary operator, a supertype of A.
op: A binary operator that must be associative.
returns: The result of applying reduce operator op between all the elements if the traversable or iterator is nonempty.

Definition Classes: TraversableOnce → GenTraversableOnce
Exceptions thrown: UnsupportedOperationException if this traversable or iterator is empty.

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

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

Note: will not terminate for infinite-sized collections.

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

B

the result type of the binary operator.

op

the binary operator.

returns

the result of inserting op between consecutive elements of this traversable or iterator, going left to right:

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

where x₁, ..., 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.

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.

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.

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.

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.

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

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.

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

def to[Col[_]]: Col[A]

[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

def toArray: Array[A]

[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

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

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

Note: will not terminate for infinite-sized collections.

returns: a buffer containing all elements of this traversable or iterator.

Definition Classes: TraversableOnce → GenTraversableOnce

def toIndexedSeq: immutable.IndexedSeq[A]

Converts this traversable or iterator to an indexed sequence.

Note: will not terminate for infinite-sized collections.

returns: an indexed sequence containing all elements of this traversable or iterator.

Definition Classes: TraversableOnce → GenTraversableOnce

def toIterable: Iterable[A]

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.

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. 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

def toSeq: Seq[A]

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.

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.

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.

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

© 2002-2019 EPFL, with contributions from Lightbend.
Licensed under the Apache License, Version 2.0.
https://www.scala-lang.org/api/2.12.9/scala/collection/TraversableOnce.html