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
- Alphabetic
- By Inheritance
- TraversableOnce
- GenTraversableOnce
- Any
- by MonadOps
- by any2stringadd
- by StringFormat
- by Ensuring
- by ArrowAssoc
- by alternateImplicit
- Hide All
- Show All
- Public
- All
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
trueif the given predicatepis satisfied by at least one element of this traversable or iterator, otherwisefalse
- 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, orNoneif 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
trueif this traversable or iterator is empty or the given predicatepholds for all elements of this traversable or iterator, otherwisefalse.
- 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 returnstrueif all elements have been computed. It returnsfalseif the stream is not yet evaluated to the end. Non-empty Iterators usually returnfalseeven 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
hasDefiniteSizereturnstrue. However, checkinghasDefiniteSizecan provide an assurance that size is well-defined and non-termination is not a concern.- returns
trueif this collection is known to have finite size,falseotherwise.
- 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
isEmptyis called.- returns
trueif the traversable or iterator contains no elements,falseotherwise.
- 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
trueif it is repeatedly traversable,falseotherwise.
- 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
trueif !(this == that), false otherwise.
- Definition Classes
- Any
-
final
def
##(): Int
Equivalent to
x.hashCodeexcept for boxed numeric types andnull.Equivalent to
x.hashCodeexcept for boxed numeric types andnull. 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. Fornullreturns a hashcode wherenull.hashCodethrows aNullPointerException.- 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.
Applies a binary operator to a start value and all elements of this traversable or iterator, going left to right.
Note:
/:is alternate syntax forfoldLeft;z /: xsis the same asxs 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
opbetween consecutive elements of this traversable or iterator, going left to right with the start valuezon the left:op(...op(op(z, x_1), x_2), ..., x_n)
where
x1, ..., xnare 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.
Applies a binary operator to all elements of this traversable or iterator and a start value, going right to left.
Note:
:\is alternate syntax forfoldRight;xs :\ zis the same asxs 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
opbetween consecutive elements of this traversable or iterator, going right to left with the start valuezon the right:op(x_1, op(x_2, ... op(x_n, z)...))
where
x1, ..., xnare the elements of this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
final
def
==(arg0: Any): Boolean
Test two objects for equality.
Test two objects for equality. The expression
x == thatis equivalent toif (x eq null) that eq null else x.equals(that).- returns
trueif the receiver object is equivalent to the argument;falseotherwise.
- 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
bto 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 stringsep.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
bto 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
startand ends with the stringend. Inside, the string representations (w.r.t. the methodtoString) of all elements of this traversable or iterator are separated by the stringsep.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
bto 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
foldandreduce. It is similar tofoldLeftin 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.aggregatesplits the traversable or iterator into partitions and processes each partition by sequentially applyingseqop, starting withz(likefoldLeft). Those intermediate results are then combined by usingcombop(likefold). The implementation of this operation may operate on an arbitrary number of collection partitions (even 1), socombopmay 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,
seqoptransforms each input character to an Int and adds it to the sum (of the partition). Then,combopjust 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
seqopoperator (e.g.Nilfor list concatenation or0for 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 aClassCastExceptionat runtime, while the expressionList(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
ClassCastExceptionif the receiver object is not an instance of the erasure of typeT0.
-
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
Noneif none exists.
Seq("a", 1, 5L).collectFirst({ case x: Int => x*10 }) = Some(10)
Example: -
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
xswith 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.
[use case]Copies the elements of this traversable or iterator to an array. Fills the given array
xswith values of this traversable or iterator, beginning at indexstart. 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.
[use case]Copies the elements of this traversable or iterator to an array. Fills the given array
xswith at mostlenelements of this traversable or iterator, starting at positionstart. Copying will stop once either the end of the current traversable or iterator is reached, or the end of the target array is reached, orlenelements 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.
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
xof typeAny,x.equals(x)should returntrue. - It is symmetric: for any instances
xandyof typeAny,x.equals(y)should returntrueif and only ify.equals(x)returnstrue. - It is transitive: for any instances
x,y, andzof typeAnyifx.equals(y)returnstrueandy.equals(z)returnstrue, thenx.equals(z)should returntrue.
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
hashCodeto ensure that objects which are "equal" (o1.equals(o2)returnstrue) hash to the same scala.Int. (o1.hashCode.equals(o2.hashCode)).- returns
trueif the receiver object is equivalent to the argument;falseotherwise.
- Definition Classes
- Any
- It is reflexive: for any instance
-
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.,
Nilfor 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
opbetween all the elements andz, orzif 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
opbetween consecutive elements of this traversable or iterator, going left to right with the start valuezon the left:op(...op(z, x_1), x_2, ..., x_n)
where
x1, ..., xnare the elements of this traversable or iterator. Returnszif 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
opbetween consecutive elements of this traversable or iterator, going right to left with the start valuezon the right:op(x_1, op(x_2, ... op(x_n, z)...))
where
x1, ..., xnare the elements of this traversable or iterator. Returnszif this traversable or iterator is empty.
- Definition Classes
- TraversableOnce → GenTraversableOnce
-
abstract
def
foreach(f: (A) ⇒ Unit): Unit
[use case] Applies a function
fto all elements of this traversable or iterator.[use case]Applies a function
fto 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
fis discarded.
- Definition Classes
- TraversableOnce → GenTraversableOnce
Full Signatureabstract def foreach[U](f: (A) ⇒ U): Unit
-
def
formatted(fmtstr: String): String
Returns string formatted according to given
formatstring.Returns string formatted according to given
formatstring. Format strings are as forString.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.
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)returnsfalse). A degenerate implementation could always return0. However, it is required that if two objects are equal (o1.equals(o2)returnstrue) 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 theequalsmethod.- 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 returnfalse, while the expressionList(1).isInstanceOf[List[String]]will returntrue. 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
trueif the receiver object is an instance of erasure of typeT0;falseotherwise.
- 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
- Exceptions thrown
UnsupportedOperationExceptionif this traversable or iterator is empty.
Full Signaturedef max[B >: A](implicit cmp: Ordering[B]): A
-
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
- Exceptions thrown
UnsupportedOperationExceptionif this traversable or iterator is empty.
Full Signaturedef maxBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A
-
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
- Exceptions thrown
UnsupportedOperationExceptionif this traversable or iterator is empty.
Full Signaturedef min[B >: A](implicit cmp: Ordering[B]): A
-
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
- Exceptions thrown
UnsupportedOperationExceptionif this traversable or iterator is empty.
Full Signaturedef minBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A
-
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 stringsep.
- Definition Classes
- TraversableOnce → GenTraversableOnce
List(1, 2, 3).mkString("|") = "1|2|3"
Example: -
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
startand ends with the stringend. Inside, the string representations (w.r.t. the methodtoString) of all elements of this traversable or iterator are separated by the stringsep.
- Definition Classes
- TraversableOnce → GenTraversableOnce
List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"
Example: -
def
nonEmpty: Boolean
Tests whether the traversable or iterator is not empty.
Tests whether the traversable or iterator is not empty.
- returns
trueif the traversable or iterator contains at least one element,falseotherwise.
- 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 ofInt, any other typeTwith an implicitNumeric[T]implementation can be used as element type of the traversable or iterator and as result type ofproduct. Examples of such types are:Long,Float,Double,BigInt.
- Definition Classes
- TraversableOnce → GenTraversableOnce
Full Signaturedef 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
opbetween all the elements if the traversable or iterator is nonempty.
- Definition Classes
- TraversableOnce → GenTraversableOnce
- Exceptions thrown
UnsupportedOperationExceptionif 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
opbetween 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, ..., xnare the elements of this traversable or iterator.
- Exceptions thrown
UnsupportedOperationExceptionif 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,Noneotherwise.
- 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
opbetween all the elements if the collection is nonempty, andNoneotherwise.
- 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
opbetween 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, ..., xnare the elements of this traversable or iterator.
- Definition Classes
- TraversableOnce → GenTraversableOnce
- Exceptions thrown
UnsupportedOperationExceptionif 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,Noneotherwise.
- 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 ofInt, any other typeTwith an implicitNumeric[T]implementation can be used as element type of the traversable or iterator and as result type ofsum. Examples of such types are:Long,Float,Double,BigInt.
- Definition Classes
- TraversableOnce → GenTraversableOnce
Full Signaturedef 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 Signaturedef 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
ClassTagmust 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.
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
Iterableis lazy in this default implementation as thisTraversableOncemay 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
Iterablecontaining 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 Signaturedef 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 thisTraversableOncemay 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
This is the documentation for the Scala standard library.
Package structure
The scala package contains core types like
Int,Float,ArrayorOptionwhich are accessible in all Scala compilation units without explicit qualification or imports.Notable packages include:
scala.collectionand its sub-packages contain Scala's collections frameworkscala.collection.immutable- Immutable, sequential data-structures such asVector,List,Range,HashMaporHashSetscala.collection.mutable- Mutable, sequential data-structures such asArrayBuffer,StringBuilder,HashMaporHashSetscala.collection.concurrent- Mutable, concurrent data-structures such asTrieMapscala.collection.parallel.immutable- Immutable, parallel data-structures such asParVector,ParRange,ParHashMaporParHashSetscala.collection.parallel.mutable- Mutable, parallel data-structures such asParArray,ParHashMap,ParTrieMaporParHashSetscala.concurrent- Primitives for concurrent programming such asFuturesandPromisesscala.io- Input and output operationsscala.math- Basic math functions and additional numeric types likeBigIntandBigDecimalscala.sys- Interaction with other processes and the operating systemscala.util.matching- Regular expressionsOther packages exist. See the complete list on the right.
Additional parts of the standard library are shipped as separate libraries. These include:
scala.reflect- Scala's reflection API (scala-reflect.jar)scala.xml- XML parsing, manipulation, and serialization (scala-xml.jar)scala.swing- A convenient wrapper around Java's GUI framework called Swing (scala-swing.jar)scala.util.parsing- Parser combinators (scala-parser-combinators.jar)Automatic imports
Identifiers in the scala package and the
scala.Predefobject are always in scope by default.Some of these identifiers are type aliases provided as shortcuts to commonly used classes. For example,
Listis an alias forscala.collection.immutable.List.Other aliases refer to classes provided by the underlying platform. For example, on the JVM,
Stringis an alias forjava.lang.String.