GenTraversableOnce

trait GenTraversableOnce[+A] extends AnyRef

A template trait for all traversable-once objects which may be traversed in parallel.

Methods in this trait are either abstract or can be implemented in terms of other methods.

Source
GenTraversableOnce.scala
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Abstract Value Members

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

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

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

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

Examples:

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

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

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

Note: will not terminate for infinite-sized collections.

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

B

the result type of the binary operator.

z

the start value.

op

the binary operator.

returns

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

op(...op(op(z, x1), x2), ..., xn)

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

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

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

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

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

Note: will not terminate for infinite-sized collections.

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

Examples:

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

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

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

B

the result type of the binary operator.

z

the start value

op

the binary operator

returns

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

op(x1, op(x2, ... op(xn, z)...))

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

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

Aggregates the results of applying an operator to subsequent elements.

Aggregates the results of applying an operator to subsequent elements.

This is a more general form of fold and reduce. It has similar semantics, but does not require the result to be a supertype of the element type. It traverses the elements in different partitions sequentially, using seqop to update the result, and then applies combop to results from different partitions. The implementation of this operation may operate on an arbitrary number of collection partitions, so combop may be invoked an arbitrary number of times.

For example, one might want to process some elements and then produce a Set. In this case, seqop would process an element and append it to the list, while combop would concatenate two lists from different partitions together. The initial value z would be an empty set.

pc.aggregate(Set[Int]())(_ += process(_), _ ++ _)

Another example is calculating geometric mean from a collection of doubles (one would typically require big doubles for this).

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)

seqop

an operator used to accumulate results within a partition

combop

an associative operator used to combine results from different partitions

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

Copies values of this collection or iterator to an array.

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

Note: will not terminate for infinite-sized collections.

B

the type of the elements of the array.

xs

the array to fill.

start

the starting index.

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

Copies values of this collection or iterator to an array.

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

Note: will not terminate for infinite-sized collections.

B

the type of the elements of the array.

xs

the array to fill.

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

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

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

p

the predicate used to test elements.

returns

the number of elements satisfying the predicate p.

9. abstract def find(pred: (A) ⇒ Boolean): Option[A]

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

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

Note: may not terminate for infinite-sized collections.

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

returns

an option value containing the first element in the collection or iterator that satisfies p, or None if none exists.

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

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

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

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

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 fold operator op between all the elements and z

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

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

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

Note: will not terminate for infinite-sized collections.

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

B

the result type of the binary operator.

z

the start value.

op

the binary operator.

returns

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

op(...op(z, x1), x2, ..., xn)

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

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

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

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

Note: will not terminate for infinite-sized collections.

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

B

the result type of the binary operator.

z

the start value.

op

the binary operator.

returns

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

op(x1, op(x2, ... op(xn, z)...))

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

16. abstract def isEmpty: Boolean

Tests whether the collection or iterator is empty.

Tests whether the collection or iterator is empty.

returns

true if the collection or iterator contains no elements, false otherwise.

17. 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.

18. abstract def max[A1 >: A](implicit ord: Ordering[A1]): A

Finds the largest element.

Finds the largest element.

returns

the largest element of this collection or iterator with respect to the ordering cmp.

20. abstract def min[A1 >: A](implicit ord: Ordering[A1]): A

Finds the smallest element.

Finds the smallest element.

returns

the smallest element of this collection or iterator with respect to the ordering cmp.

22. abstract def mkString: String

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

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

returns

a string representation of this collection or iterator. In the resulting string the string representations (w.r.t. the method toString) of all elements of this collection or iterator follow each other without any separator string.

23. abstract def mkString(sep: String): String

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

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

sep

the separator string.

returns

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

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

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

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

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

start

the starting string.

sep

the separator string.

end

the ending string.

returns

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

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

25. abstract def nonEmpty: Boolean

Tests whether the collection or iterator is not empty.

Tests whether the collection or iterator is not empty.

returns

true if the collection or iterator contains at least one element, false otherwise.

26. abstract def product[A1 >: A](implicit num: Numeric[A1]): A1

Multiplies up the elements of this collection.

Multiplies up the elements of this collection.

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 or iterator with respect to the * operator in num.

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

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

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

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

A1

A type parameter for the binary operator, a supertype of A.

op

A binary operator that must be associative.

returns

The result of applying reduce operator op between all the elements if the collection or iterator is nonempty.

Exceptions thrown
UnsupportedOperationException

if this collection or iterator is empty.

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

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

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

Note: will not terminate for infinite-sized collections.

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

B

the result type of the binary operator.

op

the binary operator.

returns

an option value containing the result of reduceLeft(op) is this collection or iterator is nonempty, None otherwise.

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

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

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

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

A1

A type parameter for the binary operator, a supertype of A.

op

A binary operator that must be associative.

returns

An option value containing result of applying reduce operator op between all the elements if the collection is nonempty, and None otherwise.

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

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

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

Note: will not terminate for infinite-sized collections.

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

B

the result type of the binary operator.

op

the binary operator.

returns

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

op(x,,1,,, op(x,,2,,, ..., op(x,,n-1,,, x,,n,,)...))

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

Exceptions thrown
`UnsupportedOperationException`

if this collection or iterator is empty.

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

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

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

Note: will not terminate for infinite-sized collections.

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

B

the result type of the binary operator.

op

the binary operator.

returns

an option value containing the result of reduceRight(op) is this collection or iterator is nonempty, None otherwise.

33. abstract def size: Int

The size of this collection or iterator.

The size of this collection or iterator.

Note: will not terminate for infinite-sized collections.

returns

the number of elements in this collection or iterator.

34. abstract def sum[A1 >: A](implicit num: Numeric[A1]): A1

Sums up the elements of this collection.

Sums up the elements of this collection.

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 or iterator with respect to the + operator in num.

35. abstract def toArray[A1 >: A](implicit arg0: ClassManifest[A1]): Array[A1]

Converts this collection or iterator to an array.

Converts this collection or iterator to an array.

Note: will not terminate for infinite-sized collections.

returns

an array containing all elements of this collection or iterator.

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

Converts this collection or iterator to a mutable buffer.

Converts this collection or iterator to a mutable buffer.

Note: will not terminate for infinite-sized collections.

returns

a buffer containing all elements of this collection or iterator.

37. abstract def toIndexedSeq[A1 >: A]: IndexedSeq[A1]

Converts this collection or iterator to an indexed sequence.

Converts this collection or iterator to an indexed sequence.

Note: will not terminate for infinite-sized collections.

returns

an indexed sequence containing all elements of this collection or iterator.

38. abstract def toIterable: GenIterable[A]

Converts this collection or iterator to an iterable collection.

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

Note: will not terminate for infinite-sized collections.

returns

an Iterable containing all elements of this collection or iterator.

39. 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.

40. abstract def toList: List[A]

Converts this collection or iterator to a list.

Converts this collection or iterator to a list.

Note: will not terminate for infinite-sized collections.

returns

a list containing all elements of this collection or iterator.

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

Converts this collection or iterator to a map.

Converts this collection 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 containing all elements of this collection or iterator.

42. abstract def toSeq: GenSeq[A]

Converts this collection or iterator to a sequence.

Converts this collection 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 collection or iterator.

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

Converts this collection or iterator to a set.

Converts this collection or iterator to a set.

Note: will not terminate for infinite-sized collections.

returns

a set containing all elements of this collection or iterator.

44. abstract def toStream: Stream[A]

Converts this collection or iterator to a stream.

Converts this collection or iterator to a stream.

Note: will not terminate for infinite-sized collections.

returns

a stream containing all elements of this collection or iterator.

45. abstract def toTraversable: GenTraversable[A]

Converts this collection or iterator to an unspecified Traversable.

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

Note: will not terminate for infinite-sized collections.

returns

a Traversable containing all elements of this collection or iterator.

Concrete Value Members

1. final def !=(arg0: AnyRef): Boolean

Definition Classes
AnyRef
2. 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
3. final def ##(): Int

Equivalent to x.hashCode except for boxed numeric types.

Equivalent to x.hashCode except for boxed numeric types. 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.

returns

a hash value consistent with ==

Definition Classes
AnyRef → Any
4. def /:\[A1 >: A](z: A1)(op: (A1, A1) ⇒ A1): A1

A syntactic sugar for out of order folding.

A syntactic sugar for out of order folding. See fold.

Example:

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

5. final def ==(arg0: AnyRef): Boolean

Definition Classes
AnyRef
6. final def ==(arg0: Any): Boolean

Test two objects for equality.

Test two objects for equality.

returns

true if the receiver object is equivalent to the argument; false otherwise.

Definition Classes
Any
7. 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

Definition Classes
Any
Exceptions thrown
ClassCastException

if the receiver object is not an instance of the erasure of type T0.

8. def clone(): AnyRef

Create a copy of the receiver object.

Create a copy of the receiver object.

The default implementation of the clone method is platform dependent.

returns

a copy of the receiver object.

Attributes
protected[lang]
Definition Classes
AnyRef
Annotations
()
Note

not specified by SLS as a member of AnyRef

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

[use case] Copies values of this collection or iterator to an array.

[use case]

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

xs

the array to fill.

start

the starting index.

10. abstract def copyToArray(xs: Array[A]): Unit

[use case] Copies values of this collection or iterator to an array.

[use case]

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

xs

the array to fill.

11. final def eq(arg0: AnyRef): Boolean

Tests whether the argument (arg0) is a reference to the receiver object (this).

Tests whether the argument (arg0) is a reference to the receiver object (this).

The eq method implements an equivalence relation on non-null instances of AnyRef, and has three additional properties:

• It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
• For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
• null.eq(null) returns true.

When overriding the equals or hashCode methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).

returns

true if the argument is a reference to the receiver object; false otherwise.

Definition Classes
AnyRef
12. def equals(arg0: Any): Boolean

The equality method for reference types.

The equality method for reference types. See equals in Any.

returns

true if the receiver object is equivalent to the argument; false otherwise.

Definition Classes
AnyRef → Any
13. def finalize(): Unit

Called by the garbage collector on the receiver object when there are no more references to the object.

Called by the garbage collector on the receiver object when there are no more references to the object.

The details of when and if the finalize method is invoked, as well as the interaction between finalize and non-local returns and exceptions, are all platform dependent.

Attributes
protected[lang]
Definition Classes
AnyRef
Annotations
()
Note

not specified by SLS as a member of AnyRef

14. final def getClass(): java.lang.Class[_]

A representation that corresponds to the dynamic class of the receiver object.

A representation that corresponds to the dynamic class of the receiver object.

The nature of the representation is platform dependent.

returns

a representation that corresponds to the dynamic class of the receiver object.

Definition Classes
AnyRef → Any
Note

not specified by SLS as a member of AnyRef

15. def hashCode(): Int

The hashCode method for reference types.

The hashCode method for reference types. See hashCode in Any.

returns

the hash code value for this object.

Definition Classes
AnyRef → Any
16. 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
17. abstract def max: A

[use case] Finds the largest element.

[use case]

Finds the largest element.

returns

the largest element of this collection or iterator with respect to the ordering cmp.

18. abstract def min: A

[use case] Finds the smallest element.

[use case]

Finds the smallest element.

returns

the smallest element of this collection or iterator with respect to the ordering cmp.

19. final def ne(arg0: AnyRef): Boolean

Equivalent to !(this eq that).

Equivalent to !(this eq that).

returns

true if the argument is not a reference to the receiver object; false otherwise.

Definition Classes
AnyRef
20. final def notify(): Unit

Wakes up a single thread that is waiting on the receiver object's monitor.

Wakes up a single thread that is waiting on the receiver object's monitor.

Definition Classes
AnyRef
Note

not specified by SLS as a member of AnyRef

21. final def notifyAll(): Unit

Wakes up all threads that are waiting on the receiver object's monitor.

Wakes up all threads that are waiting on the receiver object's monitor.

Definition Classes
AnyRef
Note

not specified by SLS as a member of AnyRef

22. abstract 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 of this collection or iterator with respect to the * operator in num.

23. abstract 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 of this collection or iterator with respect to the + operator in num.

24. final def synchronized[T0](arg0: ⇒ T0): T0

Definition Classes
AnyRef
25. abstract def toArray: Array[A]

[use case] Converts this collection or iterator to an array.

[use case]

Converts this collection or iterator to an array.

Note: will not terminate for infinite-sized collections.

returns

an array containing all elements of this collection or iterator.

26. abstract def toMap[T, U]: Map[T, U]

[use case] Converts this collection or iterator to a map.

[use case]

Converts this collection 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 containing all elements of this collection or iterator.

27. def toString(): String

Creates a String representation of this object.

Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.

returns

a String representation of the object.

Definition Classes
AnyRef → Any
28. final def wait(): Unit

Definition Classes
AnyRef
Annotations
()
29. final def wait(arg0: Long, arg1: Int): Unit

Definition Classes
AnyRef
Annotations
()
30. final def wait(arg0: Long): Unit

Definition Classes
AnyRef
Annotations
()