The type implementing this traversable
The type implementing this traversable
A class supporting filtered operations.
Creates a new builder for this collection type.
Creates a new builder for this collection type.
A version of this collection with all of the operations implemented sequentially (i.
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.
a sequential view of the collection.
[use case] Returns a new sequence containing the elements from the left hand operand followed by the elements from the right hand operand.
Returns a new sequence containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the sequence is the most specific superclass encompassing the element types of the two operands.
Example:
scala> val a = List(1) a: List[Int] = List(1) scala> val b = List(2) b: List[Int] = List(2) scala> val c = a ++ b c: List[Int] = List(1, 2) scala> val d = List('a') d: List[Char] = List(a) scala> val e = c ++ d e: List[AnyVal] = List(1, 2, a)
the element type of the returned collection.
the traversable to append.
a new sequence which contains all elements of this sequence
followed by all elements of that
.
As with ++
, returns a new collection containing the elements from the
left operand followed by the elements from the right operand.
As with ++
, returns a new collection containing the elements from the
left operand followed by the elements from the right operand.
It differs from ++
in that the right operand determines the type of
the resulting collection rather than the left one.
Mnemonic: the COLon is on the side of the new COLlection type.
Example:
scala> val x = List(1) x: List[Int] = List(1) scala> val y = LinkedList(2) y: scala.collection.mutable.LinkedList[Int] = LinkedList(2) scala> val z = x ++: y z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)
This overload exists because: for the implementation of ++:
we should
reuse that of ++
because many collections override it with more
efficient versions.
Since TraversableOnce
has no ++
method, we have to implement that
directly, but Traversable
and down can use the overload.
the element type of the returned collection.
the class of the returned collection. Where possible, That
is
the same class as the current collection class Repr
, but this
depends on the element type B
being admissible for that class,
which means that an implicit instance of type CanBuildFrom[Repr, B, That]
is found.
the traversable to append.
an implicit value of class CanBuildFrom
which determines
the result class That
from the current representation type Repr
and
and the new element type B
.
a new collection of type That
which contains all elements
of this traversable collection followed by all elements of that
.
[use case] As with ++
, returns a new collection containing the elements from the left operand followed by the
elements from the right operand.
As with ++
, returns a new collection containing the elements from the left operand followed by the
elements from the right operand.
It differs from ++
in that the right operand determines the type of
the resulting collection rather than the left one.
Mnemonic: the COLon is on the side of the new COLlection type.
Example:
scala> val x = List(1) x: List[Int] = List(1) scala> val y = LinkedList(2) y: scala.collection.mutable.LinkedList[Int] = LinkedList(2) scala> val z = x ++: y z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)
the element type of the returned collection.
the traversable to append.
a new sequence which contains all elements of this sequence
followed by all elements of that
.
[use case] A copy of the sequence with an element prepended.
A copy of the sequence with an element prepended.
Note that :-ending operators are right associative (see example).
A mnemonic for +:
vs. :+
is: the COLon goes on the COLlection side.
Also, the original sequence is not modified, so you will want to capture the result.
Example:
scala> val x = List(1) x: List[Int] = List(1) scala> val y = 2 +: x y: List[Int] = List(2, 1) scala> println(x) List(1)
the prepended element
a new sequence consisting of elem
followed
by all elements of this sequence.
Applies a binary operator to a start value and all elements of this traversable or iterator, going left to right.
Applies a binary operator to a start value and all elements of this traversable or iterator, going left to right.
Note: /:
is alternate syntax for foldLeft
; z /: xs
is the same as
xs foldLeft z
.
Examples:
Note that the folding function used to compute b is equivalent to that used to compute c.
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = (5 /: a)(_+_) b: Int = 15 scala> val c = (5 /: a)((x,y) => x + y) c: Int = 15
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
the result type of the binary operator.
the start value.
the binary operator.
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 x_{1}, ..., x_{n}
are the elements of this traversable or iterator.
[use case] A copy of this sequence with an element appended.
A copy of this sequence with an element appended.
A mnemonic for +:
vs. :+
is: the COLon goes on the COLlection side.
Note: will not terminate for infinite-sized collections.
Example:
scala> val a = List(1) a: List[Int] = List(1) scala> val b = a :+ 2 b: List[Int] = List(1, 2) scala> println(a) List(1)
the appended element
a new sequence consisting of
all elements of this sequence followed by elem
.
Applies a binary operator to all elements of this traversable or iterator and a start value, going right to left.
Applies a binary operator to all elements of this traversable or iterator and a start value, going right to left.
Note: :\
is alternate syntax for foldRight
; xs :\ z
is the same as
xs foldRight z
.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
Examples:
Note that the folding function used to compute b is equivalent to that used to compute c.
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = (a :\ 5)(_+_) b: Int = 15 scala> val c = (a :\ 5)((x,y) => x + y) c: Int = 15
the result type of the binary operator.
the start value
the binary operator
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 x_{1}, ..., x_{n}
are the elements of this traversable or iterator.
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
the string builder to which elements are appended.
the string builder b
to which elements were appended.
Appends all elements of this traversable or iterator to a string builder using a separator string.
Appends all elements of this traversable or iterator to a string builder using a separator string.
The written text consists of the string representations (w.r.t. the method toString
)
of all elements of this traversable or iterator, separated by the string sep
.
Example:
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = new StringBuilder() b: StringBuilder = scala> a.addString(b, ", ") res0: StringBuilder = 1, 2, 3, 4
the string builder to which elements are appended.
the separator string.
the string builder b
to which elements were appended.
Appends all elements of this traversable or iterator to a string builder using start, end, and separator strings.
Appends all elements of this traversable or iterator to a string builder using start, end, and separator strings.
The written text begins with the string start
and ends with the string end
.
Inside, the string representations (w.r.t. the method toString
)
of all elements of this traversable or iterator are separated by the string sep
.
Example:
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = new StringBuilder() b: StringBuilder = scala> a.addString(b , "List(" , ", " , ")") res5: StringBuilder = List(1, 2, 3, 4)
the string builder to which elements are appended.
the starting string.
the separator string.
the ending string.
the string builder b
to which elements were appended.
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).
the type of accumulated results
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
an operator used to accumulate results within a partition
an associative operator used to combine results from different partitions
Selects an element by its index in the sequence.
Selects an element by its index in the sequence.
Note: the execution of apply
may take time proportial to the index value.
the element of this sequence at index idx
, where 0
indicates the first element.
if idx
does not satisfy 0 <= idx < length
.
Method called from equality methods, so that user-defined subclasses can refuse to be equal to other collections of the same kind.
Method called from equality methods, so that user-defined subclasses can refuse to be equal to other collections of the same kind.
The object with which this iterable collection should be compared
true
, if this iterable collection can possibly equal that
, false
otherwise. The test
takes into consideration only the run-time types of objects but ignores their elements.
[use case] Builds a new collection by applying a partial function to all elements of this sequence on which the function is defined.
Builds a new collection by applying a partial function to all elements of this sequence on which the function is defined.
the element type of the returned collection.
the partial function which filters and maps the sequence.
a new sequence resulting from applying the given partial function
pf
to each element on which it is defined and collecting the results.
The order of the elements is preserved.
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.
the partial function
an option value containing pf applied to the first
value for which it is defined, or None
if none exists.
Seq("a", 1, 5L).collectFirst({ case x: Int => x*10 }) = Some(10)
Iterates over combinations.
Iterates over combinations.
An Iterator which traverses the possible n-element combinations of this sequence.
"abbbc".combinations(2) = Iterator(ab, ac, bb, bc)
Tests whether this sequence contains a given value as an element.
Tests whether this sequence contains a given value as an element.
Note: may not terminate for infinite-sized collections.
the element to test.
true
if this sequence has an element that is equal (as
determined by ==
) to elem
, false
otherwise.
Tests whether this sequence contains a given sequence as a slice.
Tests whether this sequence contains a given sequence as a slice.
Note: may not terminate for infinite-sized collections.
the sequence to test
true
if this sequence contains a slice with the same elements
as that
, otherwise false
.
[use case] Copies elements of this sequence to an array.
Copies elements of this sequence to an array.
Fills the given array xs
with at most len
elements of
this sequence, starting at position start
.
Copying will stop once either the end of the current sequence is reached,
or the end of the array is reached, or len
elements have been copied.
Note: will not terminate for infinite-sized collections.
the array to fill.
the starting index.
the maximal number of elements to copy.
[use case] Copies values of this sequence to an array.
Copies values of this sequence to an array.
Fills the given array xs
with values of this sequence.
Copying will stop once either the end of the current sequence is reached,
or the end of the array is reached.
Note: will not terminate for infinite-sized collections.
the array to fill.
[use case] Copies values of this sequence to an array.
Copies values of this sequence to an array.
Fills the given array xs
with values of this sequence, beginning at index start
.
Copying will stop once either the end of the current sequence is reached,
or the end of the array is reached.
Note: will not terminate for infinite-sized collections.
the array to fill.
the starting index.
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.
The buffer to which elements are copied.
Tests whether every element of this sequence relates to the corresponding element of another sequence by satisfying a test predicate.
Tests whether every element of this sequence relates to the corresponding element of another sequence by satisfying a test predicate.
the type of the elements of that
the other sequence
the test predicate, which relates elements from both sequences
true
if both sequences have the same length and
p(x, y)
is true
for all corresponding elements x
of this sequence
and y
of that
, otherwise false
.
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.
the predicate used to test elements.
the number of elements satisfying the predicate p
.
[use case] Computes the multiset difference between this sequence and another sequence.
Computes the multiset difference between this sequence and another sequence.
Note: will not terminate for infinite-sized collections.
the sequence of elements to remove
a new sequence which contains all elements of this sequence
except some of occurrences of elements that also appear in that
.
If an element value x
appears
n times in that
, then the first n occurrences of x
will not form
part of the result, but any following occurrences will.
Builds a new sequence from this sequence without any duplicate elements.
Builds a new sequence from this sequence without any duplicate elements.
Note: will not terminate for infinite-sized collections.
A new sequence which contains the first occurrence of every element of this sequence.
Selects all elements except first n ones.
Selects all elements except first n ones.
the number of elements to drop from this sequence.
a sequence consisting of all elements of this sequence except the first n
ones, or else the
empty sequence, if this sequence has less than n
elements.
Selects all elements except last n ones.
Selects all elements except last n ones.
The number of elements to take
a sequence consisting of all elements of this sequence except the last n
ones, or else the
empty sequence, if this sequence has less than n
elements.
Drops longest prefix of elements that satisfy a predicate.
Drops longest prefix of elements that satisfy a predicate.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the longest suffix of this traversable collection whose first element
does not satisfy the predicate p
.
Tests whether this sequence ends with the given sequence.
Tests whether this sequence ends with the given sequence.
Note: will not terminate for infinite-sized collections.
the sequence to test
true
if this sequence has that
as a suffix, false
otherwise.
The equals method for arbitrary sequences.
The equals method for arbitrary sequences. Compares this sequence to some other object.
The object to compare the sequence to
true
if that
is a sequence that has the same elements as
this sequence in the same order, false
otherwise
Tests whether a predicate holds for some of the elements of this sequence.
Tests whether a predicate holds for some of the elements of this sequence.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
true
if the given predicate p
holds for some of the
elements of this sequence, otherwise false
.
Selects all elements of this traversable collection which satisfy a predicate.
Selects all elements of this traversable collection which satisfy a predicate.
the predicate used to test elements.
a new traversable collection consisting of all elements of this traversable collection that satisfy the given
predicate p
. The order of the elements is preserved.
Selects all elements of this traversable collection which do not satisfy a predicate.
Selects all elements of this traversable collection which do not satisfy a predicate.
the predicate used to test elements.
a new traversable collection consisting of all elements of this traversable collection that do not satisfy the given
predicate p
. The order of the elements is preserved.
Finds the first element of the sequence satisfying a predicate, if any.
Finds the first element of the sequence satisfying a predicate, if any.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
an option value containing the first element in the sequence
that satisfies p
, or None
if none exists.
[use case] Builds a new collection by applying a function to all elements of this sequence and using the elements of the resulting collections.
Builds a new collection by applying a function to all elements of this sequence and using the elements of the resulting collections.
For example:
def getWords(lines: Seq[String]): Seq[String] = lines flatMap (line => line split "\\W+")
The type of the resulting collection is guided by the static type of sequence. This might cause unexpected results sometimes. For example:
// lettersOf will return a Seq[Char] of likely repeated letters, instead of a Set def lettersOf(words: Seq[String]) = words flatMap (word => word.toSet) // lettersOf will return a Set[Char], not a Seq def lettersOf(words: Seq[String]) = words.toSet flatMap (word => word.toSeq) // xs will be an Iterable[Int] val xs = Map("a" -> List(11,111), "b" -> List(22,222)).flatMap(_._2) // ys will be a Map[Int, Int] val ys = Map("a" -> List(1 -> 11,1 -> 111), "b" -> List(2 -> 22,2 -> 222)).flatMap(_._2)
the element type of the returned collection.
the function to apply to each element.
a new sequence resulting from applying the given collection-valued function
f
to each element of this sequence and concatenating the results.
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.
a type parameter for the binary operator, a supertype of A
.
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.)
a binary operator that must be associative
the result of applying fold operator op
between all the elements and z
Applies a binary operator to a start value and all elements of this sequence, going left to right.
Applies a binary operator to a start value and all elements of this sequence, going left to right.
Note: will not terminate for infinite-sized collections.
the result type of the binary operator.
the start value.
the result of inserting op
between consecutive elements of this sequence,
going left to right with the start value z
on the left:
op(...op(z, x_1), x_2, ..., x_n)
where x_{1}, ..., x_{n}
are the elements of this sequence.
Applies a binary operator to all elements of this sequence and a start value, going right to left.
Applies a binary operator to all elements of this sequence and a start value, going right to left.
Note: will not terminate for infinite-sized collections.
the result type of the binary operator.
the start value.
the result of inserting op
between consecutive elements of this sequence,
going right to left with the start value z
on the right:
op(x_1, op(x_2, ... op(x_n, z)...))
where x_{1}, ..., x_{n}
are the elements of this sequence.
Tests whether a predicate holds for all elements of this sequence.
Tests whether a predicate holds for all elements of this sequence.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
true
if the given predicate p
holds for all elements
of this sequence, otherwise false
.
[use case] Applies a function f
to all elements of this sequence.
Applies a function f
to all elements of this sequence.
Note: this method underlies the implementation of most other bulk operations. Subclasses should re-implement this method if a more efficient implementation exists.
the function that is applied for its side-effect to every element.
The result of function f
is discarded.
Returns string formatted according to given format
string.
Returns string formatted according to given format
string.
Format strings are as for String.format
(@see java.lang.String.format).
Partitions this traversable collection into a map of traversable collections according to some discriminator function.
Partitions this traversable collection into a map of traversable collections according to some discriminator function.
Note: this method is not re-implemented by views. This means when applied to a view it will always force the view and return a new traversable collection.
the type of keys returned by the discriminator function.
the discriminator function.
A map from keys to traversable collections such that the following invariant holds:
(xs groupBy f)(k) = xs filter (x => f(x) == k)
That is, every key k
is bound to a traversable collection of those elements x
for which f(x)
equals k
.
Partitions elements in fixed size iterable collections.
Partitions elements in fixed size iterable collections.
the number of elements per group
An iterator producing iterable collections of size size
, except the
last will be less than size size
if the elements don't divide evenly.
scala.collection.Iterator, method grouped
Tests whether this traversable collection is known to have a finite size.
Tests whether this traversable collection is known to have a finite size.
All strict collections are known to have finite size. For a non-strict
collection such as Stream
, the predicate returns true
if all
elements have been computed. It returns false
if the stream is
not yet evaluated to the end.
Note: many collection methods will not work on collections of infinite sizes.
true
if this collection is known to have finite size,
false
otherwise.
Hashcodes for Seq
produce a value from the hashcodes of all the
elements of the sequence.
Hashcodes for Seq
produce a value from the hashcodes of all the
elements of the sequence.
Selects the first element of this iterable collection.
Selects the first element of this iterable collection.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the first element of this iterable collection.
if the iterable collection is empty.
Optionally selects the first element.
Optionally selects the first element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the first element of this traversable collection if it is nonempty,
None
if it is empty.
[use case] Finds index of first occurrence of some value in this sequence after or at some start index.
Finds index of first occurrence of some value in this sequence after or at some start index.
Note: may not terminate for infinite-sized collections.
the element value to search for.
the start index
the index >= from
of the first element of this sequence that is equal (as determined by ==
)
to elem
, or -1
, if none exists.
[use case] Finds index of first occurrence of some value in this sequence.
Finds index of first occurrence of some value in this sequence.
Note: may not terminate for infinite-sized collections.
the element value to search for.
the index of the first element of this sequence that is equal (as determined by ==
)
to elem
, or -1
, if none exists.
Finds first index after or at a start index where this sequence contains a given sequence as a slice.
Finds first index after or at a start index where this sequence contains a given sequence as a slice.
Note: may not terminate for infinite-sized collections.
the sequence to test
the start index
the first index >= from
such that the elements of this sequence starting at this index
match the elements of sequence that
, or -1
of no such subsequence exists.
Finds first index where this sequence contains a given sequence as a slice.
Finds first index where this sequence contains a given sequence as a slice.
Note: may not terminate for infinite-sized collections.
the sequence to test
the first index such that the elements of this sequence starting at this index
match the elements of sequence that
, or -1
of no such subsequence exists.
Finds index of the first element satisfying some predicate after or at some start index.
Finds index of the first element satisfying some predicate after or at some start index.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
the start index
the index >= from
of the first element of this sequence that satisfies the predicate p
,
or -1
, if none exists.
Finds index of first element satisfying some predicate.
Finds index of first element satisfying some predicate.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
the index of the first element of this general sequence that satisfies the predicate p
,
or -1
, if none exists.
Produces the range of all indices of this sequence.
Produces the range of all indices of this sequence.
a Range
value from 0
to one less than the length of this sequence.
Selects all elements except the last.
Selects all elements except the last.
Note: might return different results for different runs, unless the underlying collection type is ordered.
a traversable collection consisting of all elements of this traversable collection except the last one.
if the traversable collection is empty.
Iterates over the inits of this traversable collection.
Iterates over the inits of this traversable collection. The first value will be this
traversable collection and the final one will be an empty traversable collection, with the intervening
values the results of successive applications of init
.
an iterator over all the inits of this traversable collection
List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)
[use case] Computes the multiset intersection between this sequence and another sequence.
Computes the multiset intersection between this sequence and another sequence.
Note: may not terminate for infinite-sized collections.
the sequence of elements to intersect with.
a new sequence which contains all elements of this sequence
which also appear in that
.
If an element value x
appears
n times in that
, then the first n occurrences of x
will be retained
in the result, but any following occurrences will be omitted.
Tests whether this sequence contains given index.
Tests whether this sequence contains given index.
The implementations of methods apply
and isDefinedAt
turn a Seq[A]
into
a PartialFunction[Int, A]
.
true
if this sequence contains an element at position idx
, false
otherwise.
Tests whether this sequence is empty.
Tests whether this sequence is empty.
true
if the sequence contain no elements, false
otherwise.
Tests whether this traversable collection can be repeatedly traversed.
Tests whether this traversable collection can be repeatedly traversed.
true
Creates a new iterator over all elements contained in this iterable object.
Creates a new iterator over all elements contained in this iterable object.
the new iterator
Selects the last element.
Selects the last element.
The last element of this sequence.
If the sequence is empty.
[use case] Finds index of last occurrence of some value in this sequence before or at a given end index.
Finds index of last occurrence of some value in this sequence before or at a given end index.
the element value to search for.
the end index.
the index <= end
of the last element of this sequence that is equal (as determined by ==
)
to elem
, or -1
, if none exists.
[use case] Finds index of last occurrence of some value in this sequence.
Finds index of last occurrence of some value in this sequence.
Note: will not terminate for infinite-sized collections.
the element value to search for.
the index of the last element of this sequence that is equal (as determined by ==
)
to elem
, or -1
, if none exists.
Finds last index before or at a given end index where this sequence contains a given sequence as a slice.
Finds last index before or at a given end index where this sequence contains a given sequence as a slice.
the sequence to test
the end index
the last index <= end
such that the elements of this sequence starting at this index
match the elements of sequence that
, or -1
of no such subsequence exists.
Finds last index where this sequence contains a given sequence as a slice.
Finds last index where this sequence contains a given sequence as a slice.
Note: will not terminate for infinite-sized collections.
the sequence to test
the last index such that the elements of this sequence starting a this index
match the elements of sequence that
, or -1
of no such subsequence exists.
Finds index of last element satisfying some predicate before or at given end index.
Finds index of last element satisfying some predicate before or at given end index.
the predicate used to test elements.
the index <= end
of the last element of this sequence that satisfies the predicate p
,
or -1
, if none exists.
Finds index of last element satisfying some predicate.
Finds index of last element satisfying some predicate.
Note: will not terminate for infinite-sized collections.
the predicate used to test elements.
the index of the last element of this general sequence that satisfies the predicate p
,
or -1
, if none exists.
Optionally selects the last element.
Optionally selects the last element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the last element of this traversable collection$ if it is nonempty,
None
if it is empty.
The length of the sequence.
The length of the sequence.
Note: will not terminate for infinite-sized collections.
Note: the execution of length
may take time proportial to the length of the sequence.
the number of elements in this sequence.
Compares the length of this sequence to a test value.
Compares the length of this sequence to a test value.
the test value that gets compared with the length.
A value x
where
x < 0 if this.length < len x == 0 if this.length == len x > 0 if this.length > len
The method as implemented here does not call length
directly; its running time
is O(length min len)
instead of O(length)
. The method should be overwritten
if computing length
is cheap.
[use case] Builds a new collection by applying a function to all elements of this sequence.
Builds a new collection by applying a function to all elements of this sequence.
the element type of the returned collection.
the function to apply to each element.
a new sequence resulting from applying the given function
f
to each element of this sequence and collecting the results.
[use case] Finds the largest element.
Finds the largest element.
the largest element of this sequence.
[use case] Finds the first element which yields the largest value measured by function f.
Finds the first element which yields the largest value measured by function f.
The result type of the function f.
The measuring function.
the first element of this sequence with the largest value measured by function f.
[use case] Finds the smallest element.
Finds the smallest element.
the smallest element of this sequence
[use case] Finds the first element which yields the smallest value measured by function f.
Finds the first element which yields the smallest value measured by function f.
The result type of the function f.
The measuring function.
the first element of this sequence with the smallest value measured by function f.
Displays all elements of this traversable or iterator in a string.
Displays all elements of this traversable or iterator in a string.
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.
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.
the separator string.
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
.
List(1, 2, 3).mkString("|") = "1|2|3"
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.
the starting string.
the separator string.
the ending string.
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
.
List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"
Tests whether the traversable or iterator is not empty.
Tests whether the traversable or iterator is not empty.
true
if the traversable or iterator contains at least one element, false
otherwise.
[use case] A copy of this sequence with an element value appended until a given target length is reached.
A copy of this sequence with an element value appended until a given target length is reached.
the target length
the padding value
a new sequence consisting of
all elements of this sequence followed by the minimal number of occurrences of elem
so
that the resulting sequence has a length of at least len
.
Returns a parallel implementation of this collection.
Returns a parallel implementation of this collection.
For most collection types, this method creates a new parallel collection by copying
all the elements. For these collection, par
takes linear time. Mutable collections
in this category do not produce a mutable parallel collection that has the same
underlying dataset, so changes in one collection will not be reflected in the other one.
Specific collections (e.g. ParArray
or mutable.ParHashMap
) override this default
behaviour by creating a parallel collection which shares the same underlying dataset.
For these collections, par
takes constant or sublinear time.
All parallel collections return a reference to themselves.
a parallel implementation of this collection
The default par
implementation uses the combiner provided by this method
to create a new parallel collection.
The default par
implementation uses the combiner provided by this method
to create a new parallel collection.
a combiner for the parallel collection of type ParRepr
Partitions this traversable collection in two traversable collections according to a predicate.
Partitions this traversable collection in two traversable collections according to a predicate.
the predicate on which to partition.
a pair of traversable collections: the first traversable collection consists of all elements that
satisfy the predicate p
and the second traversable collection consists of all elements
that don't. The relative order of the elements in the resulting traversable collections
is the same as in the original traversable collection.
[use case] Produces a new sequence where a slice of elements in this sequence is replaced by another sequence.
Produces a new sequence where a slice of elements in this sequence is replaced by another sequence.
the index of the first replaced element
the number of elements to drop in the original sequence
a new sequence consisting of all elements of this sequence
except that replaced
elements starting from from
are replaced
by patch
.
Iterates over distinct permutations.
Iterates over distinct permutations.
An Iterator which traverses the distinct permutations of this sequence.
"abb".permutations = Iterator(abb, bab, bba)
Returns the length of the longest prefix whose elements all satisfy some predicate.
Returns the length of the longest prefix whose elements all satisfy some predicate.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
the length of the longest prefix of this general sequence
such that every element of the segment satisfies the predicate p
.
[use case] Multiplies up the elements of this collection.
Multiplies up the elements of this collection.
the product of all elements in this sequence 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 sequence and as result type of product
.
Examples of such types are: Long
, Float
, Double
, BigInt
.
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.
A type parameter for the binary operator, a supertype of A
.
A binary operator that must be associative.
The result of applying reduce operator op
between all the elements if the traversable or iterator is nonempty.
if this traversable or iterator is empty.
Applies a binary operator to all elements of this sequence, going left to right.
Applies a binary operator to all elements of this sequence, going left to right.
Note: will not terminate for infinite-sized collections.
the result type of the binary operator.
the result of inserting op
between consecutive elements of this sequence,
going left to right:
op( op( ... op(x_1, x_2) ..., x_{n-1}), x_n)
where x_{1}, ..., x_{n}
are the elements of this sequence.
if this sequence is empty.
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.
the result type of the binary operator.
the binary operator.
an option value containing the result of reduceLeft(op)
is this traversable or iterator is nonempty,
None
otherwise.
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.
A type parameter for the binary operator, a supertype of A
.
A binary operator that must be associative.
An option value containing result of applying reduce operator op
between all
the elements if the collection is nonempty, and None
otherwise.
Applies a binary operator to all elements of this sequence, going right to left.
Applies a binary operator to all elements of this sequence, going right to left.
Note: will not terminate for infinite-sized collections.
the result type of the binary operator.
the binary operator.
the result of inserting op
between consecutive elements of this sequence,
going right to left:
op(x_1, op(x_2, ..., op(x_{n-1}, x_n)...))
where x_{1}, ..., x_{n}
are the elements of this sequence.
if this sequence is empty.
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.
the result type of the binary operator.
the binary operator.
an option value containing the result of reduceRight(op)
is this traversable or iterator is nonempty,
None
otherwise.
The collection of type traversable collection underlying this TraversableLike
object.
The collection of type traversable collection underlying this TraversableLike
object.
By default this is implemented as the TraversableLike
object itself,
but this can be overridden.
Returns new sequence with elements in reversed order.
Returns new sequence with elements in reversed order.
Note: will not terminate for infinite-sized collections.
A new sequence with all elements of this sequence in reversed order.
An iterator yielding elements in reversed order.
An iterator yielding elements in reversed order.
Note: will not terminate for infinite-sized collections.
Note: xs.reverseIterator
is the same as xs.reverse.iterator
but might be more efficient.
an iterator yielding the elements of this sequence in reversed order
[use case] Builds a new collection by applying a function to all elements of this sequence and collecting the results in reversed order.
Builds a new collection by applying a function to all elements of this sequence and collecting the results in reversed order.
Note: will not terminate for infinite-sized collections.
Note: xs.reverseMap(f)
is the same as xs.reverse.map(f)
but might be more efficient.
the element type of the returned collection.
the function to apply to each element.
a new sequence resulting from applying the given function
f
to each element of this sequence and collecting the results in reversed order.
[use case] Checks if the other iterable collection contains the same elements in the same order as this sequence.
Checks if the other iterable collection contains the same elements in the same order as this sequence.
Note: will not terminate for infinite-sized collections.
the collection to compare with.
true
, if both collections contain the same elements in the same order, false
otherwise.
Computes a prefix scan of the elements of the collection.
Computes a prefix scan of the elements of the collection.
Note: The neutral element z
may be applied more than once.
element type of the resulting collection
type of the resulting collection
neutral element for the operator op
the associative operator for the scan
combiner factory which provides a combiner
a new traversable collection containing the prefix scan of the elements in this traversable collection
Produces a collection containing cumulative results of applying the operator going left to right.
Produces a collection containing cumulative results of applying the operator 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.
the type of the elements in the resulting collection
the actual type of the resulting collection
the initial value
the binary operator applied to the intermediate result and the element
an implicit value of class CanBuildFrom
which determines
the result class That
from the current representation type Repr
and
and the new element type B
.
collection with intermediate results
Produces a collection containing cumulative results of applying the operator going right to left.
Produces a collection containing cumulative results of applying the operator going right to left. The head of the collection is the last cumulative result.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
Example:
List(1, 2, 3, 4).scanRight(0)(_ + _) == List(10, 9, 7, 4, 0)
the type of the elements in the resulting collection
the actual type of the resulting collection
the initial value
the binary operator applied to the intermediate result and the element
an implicit value of class CanBuildFrom
which determines
the result class That
from the current representation type Repr
and
and the new element type B
.
collection with intermediate results
(Changed in version 2.9.0) The behavior of scanRight
has changed. The previous behavior can be reproduced with scanRight.reverse.
Computes length of longest segment whose elements all satisfy some predicate.
Computes length of longest segment whose elements all satisfy some predicate.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
the index where the search starts.
the length of the longest segment of this sequence starting from index from
such that every element of the segment satisfies the predicate p
.
The size of this sequence, equivalent to length
.
The size of this sequence, equivalent to length
.
Note: will not terminate for infinite-sized collections.
the number of elements in this sequence.
Selects an interval of elements.
Selects an interval of elements. The returned collection is made up
of all elements x
which satisfy the invariant:
from <= indexOf(x) < until
a sequence containing the elements greater than or equal to
index from
extending up to (but not including) index until
of this sequence.
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)
the number of elements per group
the distance between the first elements of successive groups (defaults to 1)
An iterator producing iterable collections of size size
, except the
last and the only element will be truncated if there are
fewer elements than size.
scala.collection.Iterator, method sliding
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)
the number of elements per group
An iterator producing iterable collections of size size
, except the
last and the only element will be truncated if there are
fewer elements than size.
scala.collection.Iterator, method sliding
Sorts this Seq
according to the Ordering which results from transforming
an implicitly given Ordering with a transformation function.
Sorts this Seq
according to the Ordering which results from transforming
an implicitly given Ordering with a transformation function.
the target type of the transformation f
, and the type where
the ordering ord
is defined.
the transformation function mapping elements
to some other domain B
.
the ordering assumed on domain B
.
a sequence consisting of the elements of this sequence
sorted according to the ordering where x < y
if
ord.lt(f(x), f(y))
.
val words = "The quick brown fox jumped over the lazy dog".split(' ') // this works because scala.Ordering will implicitly provide an Ordering[Tuple2[Int, Char]] words.sortBy(x => (x.length, x.head)) res0: Array[String] = Array(The, dog, fox, the, lazy, over, brown, quick, jumped)
Note: will not terminate for infinite-sized collections.
Sorts this sequence according to a comparison function.
Sorts this sequence according to a comparison function.
Note: will not terminate for infinite-sized collections.
The sort is stable. That is, elements that are equal (as determined by
lt
) appear in the same order in the sorted sequence as in the original.
the comparison function which tests whether its first argument precedes its second argument in the desired ordering.
a sequence consisting of the elements of this sequence
sorted according to the comparison function lt
.
List("Steve", "Tom", "John", "Bob").sortWith(_.compareTo(_) < 0) = List("Bob", "John", "Steve", "Tom")
Sorts this sequence according to an Ordering.
Sorts this sequence according to an Ordering.
The sort is stable. That is, elements that are equal (as determined by
lt
) appear in the same order in the sorted sequence as in the original.
the ordering to be used to compare elements.
a sequence consisting of the elements of this sequence
sorted according to the ordering ord
.
Splits this sequence into a prefix/suffix pair according to a predicate.
Splits this sequence into a prefix/suffix pair according to a predicate.
Note: c span p
is equivalent to (but possibly more efficient than)
(c takeWhile p, c dropWhile p)
, provided the evaluation of the
predicate p
does not cause any side-effects.
a pair consisting of the longest prefix of this sequence whose
elements all satisfy p
, and the rest of this sequence.
Splits this traversable collection into two at a given position.
Splits this traversable collection into two at a given position.
Note: c splitAt n
is equivalent to (but possibly more efficient than)
(c take n, c drop n)
.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the position at which to split.
a pair of traversable collections consisting of the first n
elements of this traversable collection, and the other elements.
Tests whether this sequence contains the given sequence at a given index.
Tests whether this sequence contains the given sequence at a given index.
Note: If the both the receiver object this
and the argument
that
are infinite sequences this method may not terminate.
the sequence to test
the index where the sequence is searched.
true
if the sequence that
is contained in this sequence at
index offset
, otherwise false
.
Tests whether this general sequence starts with the given sequence.
Tests whether this general sequence starts with the given sequence.
the sequence to test
true
if this collection has that
as a prefix, false
otherwise.
Defines the prefix of this object's toString
representation.
Defines the prefix of this object's toString
representation.
a string representation which starts the result of toString
applied to this traversable collection. By default the string prefix is the
simple name of the collection class traversable collection.
[use case] Sums up the elements of this collection.
Sums up the elements of this collection.
the sum of all elements in this sequence 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 sequence and as result type of sum
.
Examples of such types are: Long
, Float
, Double
, BigInt
.
Selects all elements except the first.
Selects all elements except the first.
Note: might return different results for different runs, unless the underlying collection type is ordered.
a traversable collection consisting of all elements of this traversable collection except the first one.
if the traversable collection is empty.
Iterates over the tails of this traversable collection.
Iterates over the tails of this traversable collection. The first value will be this
traversable collection and the final one will be an empty traversable collection, with the intervening
values the results of successive applications of tail
.
an iterator over all the tails of this traversable collection
List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)
Selects first n elements.
Selects first n elements.
the number of elements to take from this sequence.
a sequence consisting only of the first n
elements of this sequence,
or else the whole sequence, if it has less than n
elements.
Selects last n elements.
Selects last n elements.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the number of elements to take
a iterable collection consisting only of the last n
elements of this iterable collection, or else the
whole iterable collection, if it has less than n
elements.
Takes longest prefix of elements that satisfy a predicate.
Takes longest prefix of elements that satisfy a predicate.
the longest prefix of this sequence whose elements all satisfy
the predicate p
.
The underlying collection seen as an instance of
.Seq
The underlying collection seen as an instance of
.
By default this is implemented as the current collection object itself,
but this can be overridden.
Seq
[use case] Converts this sequence into another by copying all elements.
Converts this sequence into another by copying all elements.
Note: will not terminate for infinite-sized collections.
The collection type to build.
a new collection containing all elements of this sequence.
[use case] Converts this sequence to an array.
Converts this sequence to an array.
Note: will not terminate for infinite-sized collections.
an array containing all elements of this sequence.
An ClassTag
must be available for the element type of this sequence.
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.
a buffer containing all elements of this traversable or iterator.
A conversion from collections of type Repr
to
objects.Seq
A conversion from collections of type Repr
to
objects.
By default this is implemented as just a cast, but this can be overridden.
Seq
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.
an indexed sequence containing all elements of this traversable or iterator.
Returns this iterable collection as an iterable collection.
Returns this iterable collection as an iterable collection.
A new collection will not be built; lazy collections will stay lazy.
Note: will not terminate for infinite-sized collections.
an Iterable
containing all elements of this iterable collection.
Returns an Iterator over the elements in this iterable collection.
Returns an Iterator over the elements in this iterable collection. Produces the same
result as iterator
.
Note: will not terminate for infinite-sized collections.
an Iterator containing all elements of this iterable collection.
Converts this traversable or iterator to a list.
Converts this traversable or iterator to a list.
Note: will not terminate for infinite-sized collections.
a list containing all elements of this traversable or iterator.
[use case] Converts this sequence to a map.
Converts this sequence 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.
a map of type immutable.Map[T, U]
containing all key/value pairs of type (T, U)
of this sequence.
Converts this sequence to a sequence.
Converts this sequence to a sequence.
Note: will not terminate for infinite-sized collections.
A new collection will not be built; in particular, lazy sequences will stay lazy.
a sequence containing all elements of this sequence.
Converts this traversable or iterator to a set.
Converts this traversable or iterator to a set.
Note: will not terminate for infinite-sized collections.
a set containing all elements of this traversable or iterator.
Converts this iterable collection to a stream.
Converts this iterable collection to a stream.
Note: will not terminate for infinite-sized collections.
a stream containing all elements of this iterable collection.
Converts this sequence to a string.
Converts this sequence to a string.
a string representation of this collection. By default this
string consists of the stringPrefix
of this sequence, followed
by all elements separated by commas and enclosed in parentheses.
Converts this traversable collection to an unspecified Traversable.
Converts this traversable collection to an unspecified Traversable. Will return the same collection if this instance is already Traversable.
Note: will not terminate for infinite-sized collections.
a Traversable containing all elements of this traversable collection.
Converts this traversable or iterator to a Vector.
Converts this traversable or iterator to a Vector.
Note: will not terminate for infinite-sized collections.
a vector containing all elements of this traversable or iterator.
[use case] Produces a new sequence which contains all elements of this sequence and also all elements of a given sequence.
Produces a new sequence which contains all elements of this sequence and also all elements of
a given sequence. xs union ys
is equivalent to xs ++ ys
.
Another way to express this
is that xs union ys
computes the order-presevring multi-set union of xs
and ys
.
union
is hence a counter-part of diff
and intersect
which also work on multi-sets.
Note: will not terminate for infinite-sized collections.
the sequence to add.
a new sequence which contains all elements of this sequence
followed by all elements of that
.
[use case] A copy of this sequence with one single replaced element.
A copy of this sequence with one single replaced element.
the position of the replacement
the replacing element
a copy of this sequence with the element at position index
replaced by elem
.
Creates a non-strict view of a slice of this sequence.
Creates a non-strict view of a slice of this sequence.
Note: the difference between view
and slice
is that view
produces
a view of the current sequence, whereas slice
produces a new sequence.
Note: view(from, to)
is equivalent to view.slice(from, to)
the index of the first element of the view
the index of the element following the view
a non-strict view of a slice of this sequence, starting at index from
and extending up to (but not including) index until
.
Creates a non-strict view of this sequence.
Creates a non-strict view of this sequence.
a non-strict view of this sequence.
Creates a non-strict filter of this traversable collection.
Creates a non-strict filter of this traversable collection.
Note: the difference between c filter p
and c withFilter p
is that
the former creates a new collection, whereas the latter only
restricts the domain of subsequent map
, flatMap
, foreach
,
and withFilter
operations.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the predicate used to test elements.
an object of class WithFilter
, which supports
map
, flatMap
, foreach
, and withFilter
operations.
All these operations apply to those elements of this traversable collection
which satisfy the predicate p
.
[use case] Returns a sequence formed from this sequence and another iterable collection by combining corresponding elements in pairs.
Returns a sequence formed from this sequence and another iterable collection by combining corresponding elements in pairs. If one of the two collections is longer than the other, its remaining elements are ignored.
the type of the second half of the returned pairs
The iterable providing the second half of each result pair
a new sequence containing pairs consisting of
corresponding elements of this sequence and that
. The length
of the returned collection is the minimum of the lengths of this sequence and that
.
[use case] Returns a sequence formed from this sequence and another iterable collection by combining corresponding elements in pairs.
Returns a sequence formed from this sequence and another iterable collection by combining corresponding elements in pairs. If one of the two collections is shorter than the other, placeholder elements are used to extend the shorter collection to the length of the longer.
the type of the second half of the returned pairs
The iterable providing the second half of each result pair
the element to be used to fill up the result if this sequence is shorter than that
.
the element to be used to fill up the result if that
is shorter than this sequence.
a new sequence containing pairs consisting of
corresponding elements of this sequence and that
. The length
of the returned collection is the maximum of the lengths of this sequence and that
.
If this sequence is shorter than that
, thisElem
values are used to pad the result.
If that
is shorter than this sequence, thatElem
values are used to pad the result.
[use case] Zips this sequence with its indices.
Zips this sequence with its indices.
A new sequence containing pairs consisting of all elements of this
sequence paired with their index. Indices start at 0
.
List("a", "b", "c").zipWithIndex = List(("a", 0), ("b", 1), ("c", 2))
(linearSeqOptimized: MonadOps[A]).filter(p)
(linearSeqOptimized: MonadOps[A]).flatMap(f)
(linearSeqOptimized: MonadOps[A]).map(f)
(linearSeqOptimized: MonadOps[A]).withFilter(p)
A template trait for linear sequences of type
LinearSeq[A]
which optimizes the implementation of several methods under the assumption of fast linear access.Linear sequences are defined in terms of three abstract methods, which are assumed to have efficient implementations. These are:
Here,
A
is the type of the sequence elements andRepr
is the type of the sequence itself.Linear sequences do not add any new methods to
Seq
, but promise efficient implementations of linear access patterns.