Returns a new general collection containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the general collection is the most specific superclass encompassing the element types of the two operands.
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 the new element type B
.
a new collection of type That
which contains all elements of this general collection followed by all elements of that
.
Applies a binary operator to a start value and all elements of this collection or iterator, going left to right.
Note: /:
is alternate syntax for foldLeft
; z /: xs
is the same as xs foldLeft z
.
Examples:
Note that the folding function used to compute b is equivalent to that used to compute c.
scala> val 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 collection 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 collection or iterator.
Applies a binary operator to all elements of this collection or iterator and a start value, going right to left.
Note: :\
is alternate syntax for foldRight
; xs :\ z
is the same as xs foldRight z
.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
Examples:
Note that the folding function used to compute b is equivalent to that used to compute c.
scala> val 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 collection 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 collection or iterator.
Aggregates the results of applying an operator to subsequent elements.
This is a more general form of fold
and reduce
. It is similar to foldLeft
in that it doesn't require the result to be a supertype of the element type. In addition, it allows parallel collections to be processed in chunks, and then combines the intermediate results.
aggregate
splits the collection or iterator into partitions and processes each partition by sequentially applying seqop
, starting with z
(like foldLeft
). Those intermediate results are then combined by using combop
(like fold
). The implementation of this operation may operate on an arbitrary number of collection partitions (even 1), so combop
may be invoked an arbitrary number of times (even 0).
As an example, consider summing up the integer values of a list of chars. The initial value for the sum is 0. First, seqop
transforms each input character to an Int and adds it to the sum (of the partition). Then, combop
just needs to sum up the intermediate results of the partitions:
List('a', 'b', 'c').aggregate(0)({ (sum, ch) => sum + ch.toInt }, { (p1, p2) => p1 + p2 })
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 general sequence.
Example:
scala> val x = List(1, 2, 3, 4, 5) x: List[Int] = List(1, 2, 3, 4, 5) scala> x(3) res1: Int = 4
The index to select.
the element of this general sequence at index idx
, where 0
indicates the first element.
IndexOutOfBoundsException
if idx
does not satisfy 0 <= idx < length
.
A method that should be called from every well-designed equals method that is open to be overridden in a subclass. See Programming in Scala, Chapter 28 for discussion and design.
the value being probed for possible equality
true if this instance can possibly equal that
, otherwise false
Tests whether every element of this general 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 general sequence and y
of that
, otherwise false
.
Counts the number of elements in the collection or iterator which satisfy a predicate.
the predicate used to test elements.
the number of elements satisfying the predicate p
.
Builds a new general sequence from this general sequence without any duplicate elements.
Note: will not terminate for infinite-sized collections.
A new general sequence which contains the first occurrence of every element of this general sequence.
Selects all elements except first n ones.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the number of elements to drop from this general collection.
a general collection consisting of all elements of this general collection except the first n
ones, or else the empty general collection, if this general collection has less than n
elements. If n
is negative, don't drop any elements.
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 predicate used to test elements.
the longest suffix of this general collection whose first element does not satisfy the predicate p
.
Tests whether this general sequence ends with the given sequence.
Note: will not terminate for infinite-sized collections.
the sequence to test
true
if this general sequence has that
as a suffix, false
otherwise.
Tests whether a predicate holds for at least one element of this collection or iterator.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
true
if the given predicate p
is satisfied by at least one element of this collection or iterator, otherwise false
Selects all elements of this general collection which satisfy a predicate.
the predicate used to test elements.
a new general collection consisting of all elements of this general collection that satisfy the given predicate p
. Their order may not be preserved.
Selects all elements of this general collection which do not satisfy a predicate.
the predicate used to test elements.
a new general collection consisting of all elements of this general collection that do not satisfy the given predicate p
. Their order may not be preserved.
Finds the first element of the collection or iterator satisfying a predicate, if any.
Note: may not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the predicate used to test elements.
an option value containing the first element in the collection or iterator that satisfies p
, or None
if none exists.
Folds the elements of this collection or iterator using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
Note: will not terminate for infinite-sized collections.
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 the fold operator op
between all the elements and z
, or z
if this collection or iterator is empty.
Applies a binary operator to a start value and all elements of this collection or iterator, going left to right.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
the result type of the binary operator.
the start value.
the binary operator.
the result of inserting op
between consecutive elements of this collection or iterator, going left to right with the start value z
on the left:
op(...op(z, x_1), x_2, ..., x_n)
where x_{1}, ..., x_{n}
are the elements of this collection or iterator. Returns z
if this collection or iterator is empty.
Applies a binary operator to all elements of this collection or iterator and a start value, going right to left.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
the result type of the binary operator.
the start value.
the binary operator.
the result of inserting op
between consecutive elements of this collection or iterator, going right to left with the start value z
on the right:
op(x_1, op(x_2, ... op(x_n, z)...))
where x_{1}, ..., x_{n}
are the elements of this collection or iterator. Returns z
if this collection or iterator is empty.
Tests whether a predicate holds for all elements of this collection or iterator.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
true
if this collection or iterator is empty or the given predicate p
holds for all elements of this collection or iterator, otherwise false
.
Returns the runtime class representation of the object.
a class object corresponding to the runtime type of the receiver.
Partitions this general collection into a map of general 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 general collection.
the type of keys returned by the discriminator function.
the discriminator function.
A map from keys to general 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 general collection of those elements x
for which f(x)
equals k
.
Tests whether this collection or iterator is known to have a finite size. All strict collections are known to have finite size. For a non-strict collection such as Stream
, the predicate returns true
if all elements have been computed. It returns false
if the stream is not yet evaluated to the end. Non-empty Iterators usually return false
even if they were created from a collection with a known finite size.
Note: many collection methods will not work on collections of infinite sizes. The typical failure mode is an infinite loop. These methods always attempt a traversal without checking first that hasDefiniteSize
returns true
. However, checking hasDefiniteSize
can provide an assurance that size is well-defined and non-termination is not a concern.
true
if this collection is known to have finite size, false
otherwise.
Selects the first element of this general collection.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the first element of this general collection.
NoSuchElementException
if the general collection is empty.
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 general collection if it is nonempty, None
if it is empty.
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 general sequence that satisfies the predicate p
, or -1
, if none exists.
Selects all elements except the last.
Note: might return different results for different runs, unless the underlying collection type is ordered.
a general collection consisting of all elements of this general collection except the last one.
UnsupportedOperationException
if the general collection is empty.
Tests whether the collection or iterator is empty.
Note: Implementations in subclasses that are not repeatedly traversable must take care not to consume any elements when isEmpty
is called.
true
if the collection or iterator contains no elements, false
otherwise.
Tests whether this general collection can be repeatedly traversed.
true
Selects the last element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
The last element of this general collection.
NoSuchElementException
If the general collection is empty.
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 general sequence that satisfies the predicate p
, or -1
, if none exists.
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 general collection$ if it is nonempty, None
if it is empty.
The length of the general sequence.
Note: will not terminate for infinite-sized collections.
Note: xs.length
and xs.size
yield the same result.
the number of elements in this general sequence.
IllegalArgumentException
if the length of the sequence cannot be represented in an Int
, for example, (-1 to Int.MaxValue).length
.
Displays all elements of this collection or iterator in a string.
a string representation of this collection or iterator. In the resulting string the string representations (w.r.t. the method toString
) of all elements of this collection or iterator follow each other without any separator string.
Displays all elements of this collection or iterator in a string using a separator string.
the separator string.
a string representation of this collection or iterator. In the resulting string the string representations (w.r.t. the method toString
) of all elements of this collection or iterator are separated by the string sep
.
List(1, 2, 3).mkString("|") = "1|2|3"
Displays all elements of this collection 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 collection or iterator. The resulting string begins with the string start
and ends with the string end
. Inside, the string representations (w.r.t. the method toString
) of all elements of this collection or iterator are separated by the string sep
.
List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"
Tests whether the collection or iterator is not empty.
true
if the collection or iterator contains at least one element, false
otherwise.
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 general collection in two general collections according to a predicate.
the predicate on which to partition.
a pair of general collections: the first general collection consists of all elements that satisfy the predicate p
and the second general collection consists of all elements that don't. The relative order of the elements in the resulting general collections may not be preserved.
Reduces the elements of this collection or iterator using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
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 collection or iterator is nonempty.
UnsupportedOperationException
if this collection or iterator is empty.
Optionally applies a binary operator to all elements of this collection or iterator, going left to right.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
the result type of the binary operator.
the binary operator.
an option value containing the result of reduceLeft(op)
if this collection or iterator is nonempty, None
otherwise.
Reduces the elements of this collection or iterator, if any, using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
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 collection or iterator, going right to left.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
the result type of the binary operator.
the binary operator.
the result of inserting op
between consecutive elements of this collection or iterator, going right to left:
op(x_1, op(x_2, ..., op(x_{n-1}, x_n)...))
where x_{1}, ..., x_{n}
are the elements of this collection or iterator.
UnsupportedOperationException
if this collection or iterator is empty.
Optionally applies a binary operator to all elements of this collection or iterator, going right to left.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
the result type of the binary operator.
the binary operator.
an option value containing the result of reduceRight(op)
if this collection or iterator is nonempty, None
otherwise.
Returns new general sequence with elements in reversed order.
Note: will not terminate for infinite-sized collections.
A new general sequence with all elements of this general sequence in reversed order.
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 general collection containing the prefix scan of the elements in this general collection
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 the new element type B
.
collection with intermediate results
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 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.
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 general sequence starting from index from
such that every element of the segment satisfies the predicate p
.
The size of this general collection.
Note: will not terminate for infinite-sized collections.
the number of elements in this general collection.
Selects an interval of elements. The returned collection is made up of all elements x
which satisfy the invariant:
from <= indexOf(x) < until
Note: might return different results for different runs, unless the underlying collection type is ordered.
the lowest index to include from this general collection.
the lowest index to EXCLUDE from this general collection.
a general collection containing the elements greater than or equal to index from
extending up to (but not including) index until
of this general collection.
Splits this general collection 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.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the test predicate
a pair consisting of the longest prefix of this general collection whose elements all satisfy p
, and the rest of this general collection.
Splits this general 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 general collections consisting of the first n
elements of this general collection, and the other elements.
Tests whether this general 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 general sequence at index offset
, otherwise false
.
Defines the prefix of this object's toString
representation.
a string representation which starts the result of toString
applied to this general collection. By default the string prefix is the simple name of the collection class general collection.
Selects all elements except the first.
Note: might return different results for different runs, unless the underlying collection type is ordered.
a general collection consisting of all elements of this general collection except the first one.
UnsupportedOperationException
if the general collection is empty.
Selects first n elements.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the number of elements to take from this general collection.
a general collection consisting only of the first n
elements of this general collection, or else the whole general collection, if it has less than n
elements. If n
is negative, returns an empty general collection.
Takes longest prefix of elements that satisfy a predicate.
Note: might return different results for different runs, unless the underlying collection type is ordered.
The predicate used to test elements.
the longest prefix of this general collection whose elements all satisfy the predicate p
.
Uses the contents of this collection or iterator to create a new mutable buffer.
Note: will not terminate for infinite-sized collections.
a buffer containing all elements of this collection or iterator.
Converts this collection or iterator to an indexed sequence.
Note: will not terminate for infinite-sized collections.
an indexed sequence containing all elements of this collection or iterator.
Converts this collection or iterator to an iterable collection. Note that the choice of target Iterable
is lazy in this default implementation as this TraversableOnce
may be lazy and unevaluated (i.e. it may be an iterator which is only traversable once).
Note: will not terminate for infinite-sized collections.
an Iterable
containing all elements of 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.
an Iterator containing all elements of this collection or iterator.
Converts this collection or iterator to a list.
Note: will not terminate for infinite-sized collections.
a list containing all elements of this collection or iterator.
Converts this general sequence to a sequence. As with toIterable
, it's lazy in this default implementation, as this TraversableOnce
may be lazy and unevaluated.
Note: will not terminate for infinite-sized collections.
a sequence containing all elements of this general sequence.
Converts this collection or iterator to a set.
Note: will not terminate for infinite-sized collections.
a set containing all elements of this collection or iterator.
Converts this collection or iterator to a stream.
a stream containing all elements of this collection or iterator.
Converts this collection or iterator to an unspecified Traversable. Will return the same collection if this instance is already Traversable.
Note: will not terminate for infinite-sized collections.
a Traversable containing all elements of this collection or iterator.
Converts this collection or iterator to a Vector.
Note: will not terminate for infinite-sized collections.
a vector containing all elements of this collection or iterator.
Test two objects for inequality.
true
if !(this == that), false otherwise.
Equivalent to x.hashCode
except for boxed numeric types and null
. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For null
returns a hashcode where null.hashCode
throws a NullPointerException
.
a hash value consistent with ==
A copy of the general 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 general 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 general sequence consisting of elem
followed by all elements of this general sequence.
A copy of this general 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 general sequence consisting of all elements of this general sequence followed by elem
.
Test two objects for equality. The expression x == that
is equivalent to if (x eq null) that eq null else x.equals(that)
.
true
if the receiver object is equivalent to the argument; false
otherwise.
Cast the receiver object to be of type T0
.
Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression 1.asInstanceOf[String]
will throw a ClassCastException
at runtime, while the expression List(1).asInstanceOf[List[String]]
will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.
the receiver object.
ClassCastException
if the receiver object is not an instance of the erasure of type T0
.
Builds a new collection by applying a partial function to all elements of this general sequence on which the function is defined.
the element type of the returned collection.
the partial function which filters and maps the general sequence.
a new general 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.
Copies the elements of this general sequence to an array. Fills the given array xs
with at most len
elements of this general sequence, starting at position start
. Copying will stop once either the end of the current general sequence is reached, or the end of the target array is reached, or len
elements have been copied.
Note: will not terminate for infinite-sized collections.
the array to fill.
the starting index.
the maximal number of elements to copy.
Copies the elements of this general sequence to an array. Fills the given array xs
with values of this general sequence, beginning at index start
. Copying will stop once either the end of the current general sequence is reached, or the end of the target array is reached.
Note: will not terminate for infinite-sized collections.
the array to fill.
the starting index.
Copies the elements of this general sequence to an array. Fills the given array xs
with values of this general sequence. Copying will stop once either the end of the current general sequence is reached, or the end of the target array is reached.
Note: will not terminate for infinite-sized collections.
the array to fill.
Computes the multiset difference between this general sequence and another sequence.
Note: will not terminate for infinite-sized collections.
the sequence of elements to remove
a new general sequence which contains all elements of this general 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.
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
Builds a new collection by applying a function to all elements of this general 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 general 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 general sequence resulting from applying the given collection-valued function f
to each element of this general sequence and concatenating the results.
Applies a function f
to all elements of this general sequence.
Note: this method underlies the implementation of most other bulk operations. It's important to implement this method in an efficient way.
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. Format strings are as for String.format
(@see java.lang.String.format).
Hashcodes for GenSeq produce a value from the hashcodes of all the elements of the general sequence.
the hash code value for this object.
Finds index of first occurrence of some value in this general 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 general sequence that is equal (as determined by ==
) to elem
, or -1
, if none exists.
Finds index of first occurrence of some value in this general sequence.
Note: may not terminate for infinite-sized collections.
the element value to search for.
the index of the first element of this general sequence that is equal (as determined by ==
) to elem
, or -1
, if none exists.
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.
Computes the multiset intersection between this general sequence and another sequence.
Note: may not terminate for infinite-sized collections.
the sequence of elements to intersect with.
a new general sequence which contains all elements of this general 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 general sequence contains given index.
The implementations of methods apply
and isDefinedAt
turn a Seq[A]
into a PartialFunction[Int, A]
.
the index to test
true
if this general sequence contains an element at position idx
, false
otherwise.
Test whether the dynamic type of the receiver object is T0
.
Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression 1.isInstanceOf[String]
will return false
, while the expression List(1).isInstanceOf[List[String]]
will return true
. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.
true
if the receiver object is an instance of erasure of type T0
; false
otherwise.
Finds index of last occurrence of some value in this general 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 general sequence that is equal (as determined by ==
) to elem
, or -1
, if none exists.
Finds index of last occurrence of some value in this general sequence.
Note: will not terminate for infinite-sized collections.
the element value to search for.
the index of the last element of this general sequence that is equal (as determined by ==
) to elem
, or -1
, if none exists.
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.
Builds a new collection by applying a function to all elements of this general sequence.
the element type of the returned collection.
the function to apply to each element.
a new general sequence resulting from applying the given function f
to each element of this general sequence and collecting the results.
Finds the largest element.
the largest element of this general sequence.
UnsupportedOperationException
if this general sequence is empty.
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 general sequence with the largest value measured by function f.
UnsupportedOperationException
if this general sequence is empty.
Finds the smallest element.
the smallest element of this general sequence
UnsupportedOperationException
if this general sequence is empty.
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 general sequence with the smallest value measured by function f.
UnsupportedOperationException
if this general sequence is empty.
A copy of this general sequence with an element value appended until a given target length is reached.
the target length
the padding value
a new general sequence consisting of all elements of this general sequence followed by the minimal number of occurrences of elem
so that the resulting general sequence has a length of at least len
.
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
Produces a new general sequence where a slice of elements in this general sequence is replaced by another sequence.
the index of the first replaced element
the number of elements to drop in the original general sequence
a new general sequence consisting of all elements of this general sequence except that replaced
elements starting from from
are replaced by patch
.
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
.
Multiplies up the elements of this collection.
the product of all elements in this general 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 general sequence and as result type of product
. Examples of such types are: Long
, Float
, Double
, BigInt
.
Builds a new collection by applying a function to all elements of this general 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 general sequence resulting from applying the given function f
to each element of this general sequence and collecting the results in reversed order.
Checks if the other iterable collection contains the same elements in the same order as this general sequence.
Note: might return different results for different runs, unless the underlying collection type is ordered.
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.
The size of this collection or iterator, if it can be cheaply computed
the number of elements in this collection or iterator, or -1 if the size cannot be determined cheaply
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.
Sums up the elements of this collection.
the sum of all elements in this general 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 general sequence and as result type of sum
. Examples of such types are: Long
, Float
, Double
, BigInt
.
Converts this general 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 general sequence.
Converts this general sequence to an array.
Note: will not terminate for infinite-sized collections.
an array containing all elements of this general sequence. An ClassTag
must be available for the element type of this general sequence.
Converts this general 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 general sequence.
Returns a string representation of the object.
The default representation is platform dependent.
a string representation of the object.
Produces a new sequence which contains all elements of this general 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-preserving 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 general sequence which contains all elements of this general sequence followed by all elements of that
.
A copy of this general sequence with one single replaced element.
the position of the replacement
the replacing element
a copy of this general sequence with the element at position index
replaced by elem
.
Returns a general sequence formed from this general 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.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the type of the second half of the returned pairs
The iterable providing the second half of each result pair
a new general sequence containing pairs consisting of corresponding elements of this general sequence and that
. The length of the returned collection is the minimum of the lengths of this general sequence and that
.
Returns a general sequence formed from this general 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.
Note: might return different results for different runs, unless the underlying collection type is ordered.
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 general sequence is shorter than that
.
the element to be used to fill up the result if that
is shorter than this general sequence.
a new general sequence containing pairs consisting of corresponding elements of this general sequence and that
. The length of the returned collection is the maximum of the lengths of this general sequence and that
. If this general sequence is shorter than that
, thisElem
values are used to pad the result. If that
is shorter than this general sequence, thatElem
values are used to pad the result.
Zips this general sequence with its indices.
Note: might return different results for different runs, unless the underlying collection type is ordered.
A new general sequence containing pairs consisting of all elements of this general sequence paired with their index. Indices start at 0
.
List("a", "b", "c").zipWithIndex = List(("a", 0), ("b", 1), ("c", 2))
© 2002-2019 EPFL, with contributions from Lightbend.
Licensed under the Apache License, Version 2.0.
https://www.scala-lang.org/api/2.12.9/scala/collection/GenSeqLike.html
A template trait for all sequences which may be traversed in parallel.