AbstractMap
Explicit instantiation of the Map
trait to reduce class file size in subclasses.
- Source
- Map.scala
Type members
Inherited classlikes
Value members
Inherited methods
Alias for concat
Alias for concat
- Inherited from
- IterableOps
- Source
- Iterable.scala
Appends all elements of this collection to a string builder.
Appends all elements of this collection to a string builder.
The written text consists of the string representations (w.r.t. the method
toString
) of all elements of this collection 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
- Value Params
- b
the string builder to which elements are appended.
- Returns
the string builder
b
to which elements were appended.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Appends all elements of this collection to a string builder using a separator string.
Appends all elements of this collection 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 collection, 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
- Value Params
- b
the string builder to which elements are appended.
- sep
the separator string.
- Returns
the string builder
b
to which elements were appended.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Composes this partial function with another partial function that gets applied to results of this partial function.
Composes this partial function with another partial function that gets applied to results of this partial function.
Note that calling isDefinedAt on the resulting partial function may apply the first partial function and execute its side effect. It is highly recommended to call applyOrElse instead of isDefinedAt / apply for efficiency.
- Type Params
- C
the result type of the transformation function.
- Value Params
- k
the transformation function
- Returns
a partial function with the domain of this partial function narrowed by other partial function, which maps arguments
x
tok(this(x))
.- Inherited from
- PartialFunction
- Source
- PartialFunction.scala
Composes this partial function with a transformation function that gets applied to results of this partial function.
Composes this partial function with a transformation function that gets applied to results of this partial function.
If the runtime type of the function is a PartialFunction
then the
other andThen
method is used (note its cautions).
- Type Params
- C
the result type of the transformation function.
- Value Params
- k
the transformation function
- Returns
a partial function with the domain of this partial function, possibly narrowed by the specified function, which maps arguments
x
tok(this(x))
.- Definition Classes
- Inherited from
- PartialFunction
- Source
- PartialFunction.scala
Retrieves the value which is associated with the given key.
Retrieves the value which is associated with the given key. This
method invokes the default
method of the map if there is no mapping
from the given key to a value. Unless overridden, the default
method throws a
NoSuchElementException
.
Builds a new collection by applying a partial function to all elements of this map on which the function is defined.
Builds a new collection by applying a partial function to all elements of this map on which the function is defined.
- Type Params
- K2
the key type of the returned map.
- V2
the value type of the returned map.
- Value Params
- pf
the partial function which filters and maps the map.
- Returns
a new map 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.- Inherited from
- MapOps
- Source
- Map.scala
Finds the first element of the collection for which the given partial function is defined, and applies the partial function to it.
Finds the first element of the collection 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.
- Value Params
- pf
the partial function
- Returns
an option value containing pf applied to the first value for which it is defined, or
None
if none exists.- Example
Seq("a", 1, 5L).collectFirst({ case x: Int => x*10 }) = Some(10)
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Composes another partial function k
with this partial function so that this
partial function gets applied to results of k
.
Composes another partial function k
with this partial function so that this
partial function gets applied to results of k
.
Note that calling isDefinedAt on the resulting partial function may apply the first partial function and execute its side effect. It is highly recommended to call applyOrElse instead of isDefinedAt / apply for efficiency.
- Type Params
- R
the parameter type of the transformation function.
- Value Params
- k
the transformation function
- Returns
a partial function with the domain of other partial function narrowed by this partial function, which maps arguments
x
tothis(k(x))
.- Inherited from
- PartialFunction
- Source
- PartialFunction.scala
Composes two instances of Function1 in a new Function1, with this function applied last.
Composes two instances of Function1 in a new Function1, with this function applied last.
- Type Params
- A
the type to which function
g
can be applied
- Value Params
- g
a function A => T1
- Returns
a new function
f
such thatf(x) == apply(g(x))
- Inherited from
- Function1
- Source
- Function1.scala
Returns a new iterable collection containing the elements from the left hand operand followed by the elements from the right hand operand.
Returns a new iterable collection containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the iterable collection is the most specific superclass encompassing the element types of the two operands.
- Type Params
- B
the element type of the returned collection.
- Value Params
- suffix
the traversable to append.
- Returns
a new iterable collection which contains all elements of this iterable collection followed by all elements of
suffix
.- Inherited from
- IterableOps
- Source
- Iterable.scala
Returns a new map containing the elements from the left hand operand followed by the elements from the right hand operand.
Returns a new map containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the map is the most specific superclass encompassing the element types of the two operands.
Copy elements to an array, returning the number of elements written.
Copy elements to an array, returning the number of elements written.
Fills the given array xs
starting at index start
with at most len
elements of this collection.
Copying will stop once either all the elements of this collection have been copied,
or the end of the array is reached, or len
elements have been copied.
- Type Params
- B
the type of the elements of the array.
- Value Params
- len
the maximal number of elements to copy.
- start
the starting index of xs.
- xs
the array to fill.
- Returns
the number of elements written to the array
- Note
Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Copy elements to an array, returning the number of elements written.
Copy elements to an array, returning the number of elements written.
Fills the given array xs
starting at index start
with values of this collection.
Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached.
- Type Params
- B
the type of the elements of the array.
- Value Params
- start
the starting index of xs.
- xs
the array to fill.
- Returns
the number of elements written to the array
- Note
Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Copy elements to an array, returning the number of elements written.
Copy elements to an array, returning the number of elements written.
Fills the given array xs
starting at index start
with values of this collection.
Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached.
- Type Params
- B
the type of the elements of the array.
- Value Params
- xs
the array to fill.
- Returns
the number of elements written to the array
- Note
Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Tests whether every element of this collection's iterator relates to the corresponding element of another collection by satisfying a test predicate.
Tests whether every element of this collection's iterator relates to the corresponding element of another collection by satisfying a test predicate.
Note: will not terminate for infinite-sized collections.
- Type Params
- B
the type of the elements of
that
- Value Params
- p
the test predicate, which relates elements from both collections
- that
the other collection
- Returns
true
if both collections have the same length andp(x, y)
istrue
for all corresponding elementsx
of this iterator andy
ofthat
, otherwisefalse
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Counts the number of elements in the collection which satisfy a predicate.
Counts the number of elements in the collection which satisfy a predicate.
Note: will not terminate for infinite-sized collections.
- Value Params
- p
the predicate used to test elements.
- Returns
the number of elements satisfying the predicate
p
.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Defines the default value computation for the map, returned when a key is not found The method implemented here throws an exception, but it might be overridden in subclasses.
Selects all elements except last n ones.
Selects all elements except last n ones.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- Value Params
- n
the number of elements to drop from this iterable collection.
- Returns
a iterable collection consisting of all elements of this iterable collection except the last
n
ones, or else the empty iterable collection, if this iterable collection has less thann
elements. Ifn
is negative, don't drop any elements.- Inherited from
- IterableOps
- Source
- Iterable.scala
Returns an extractor object with a unapplySeq
method, which extracts each element of a sequence data.
Returns an extractor object with a unapplySeq
method, which extracts each element of a sequence data.
- Example
val firstChar: String => Option[Char] = _.headOption Seq("foo", "bar", "baz") match { case firstChar.unlift.elementWise(c0, c1, c2) => println(s"$c0, $c1, $c2") // Output: f, b, b }
- Inherited from
- PartialFunction
- Source
- PartialFunction.scala
Equality of maps is implemented using the lookup method get.
Equality of maps is implemented using the lookup method get. This method returns true
if
the argument
o
is aMap
,the two maps have the same size, and
for every
(key, value)
pair in this map,other.get(key) == Some(value)
.
The implementation of equals
checks the canEqual method, so subclasses of Map
can narrow down the equality
to specific map types. The Map
implementations in the standard library can all be compared, their canEqual
methods return true
.
Note: The equals
method only respects the equality laws (symmetry, transitivity) if the two maps use the same
key equivalence function in their lookup operation. For example, the key equivalence operation in a
scala.collection.immutable.TreeMap is defined by its ordering. Comparing a TreeMap
with a HashMap
leads
to unexpected results if ordering.equiv(k1, k2)
(used for lookup in TreeMap
) is different from k1 == k2
(used for lookup in HashMap
).
scala> import scala.collection.immutable._
scala> val ord: Ordering[String] = _ compareToIgnoreCase _
scala> TreeMap("A" -> 1)(ord) == HashMap("a" -> 1)
val res0: Boolean = false
scala> HashMap("a" -> 1) == TreeMap("A" -> 1)(ord)
val res1: Boolean = true
Tests whether a predicate holds for at least one element of this collection.
Tests whether a predicate holds for at least one element of this collection.
Note: may not terminate for infinite-sized collections.
- Value Params
- p
the predicate used to test elements.
- Returns
true
if the given predicatep
is satisfied by at least one element of this collection, otherwisefalse
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Finds the first element of the collection satisfying a predicate, if any.
Finds the first element of the collection 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.
- Value Params
- p
the predicate used to test elements.
- Returns
an option value containing the first element in the collection that satisfies
p
, orNone
if none exists.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Builds a new map by applying a function to all elements of this map and using the elements of the resulting collections.
Builds a new map by applying a function to all elements of this map and using the elements of the resulting collections.
Folds the elements of this collection using the specified associative binary operator.
Folds the elements of this collection using the specified associative binary operator.
The default implementation in IterableOnce
is equivalent to foldLeft
but may be
overridden for more efficient traversal orders.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
Note: will not terminate for infinite-sized collections.
- Type Params
- A1
a type parameter for the binary operator, a supertype of
A
.
- Value Params
- op
a binary operator that must be associative.
- z
a neutral element for the fold operation; may be added to the result an arbitrary number of times, and must not change the result (e.g.,
Nil
for list concatenation, 0 for addition, or 1 for multiplication).
- Returns
the result of applying the fold operator
op
between all the elements andz
, orz
if this collection is empty.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Applies a binary operator to a start value and all elements of this collection, going left to right.
Applies a binary operator to a start value and all elements of this collection, 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.
- Type Params
- B
the result type of the binary operator.
- Value Params
- op
the binary operator.
- z
the start value.
- Returns
the result of inserting
op
between consecutive elements of this collection, going left to right with the start valuez
on the left:op(...op(z, x1), x2, ..., xn)
wherex1, ..., xn
are the elements of this collection. Returnsz
if this collection is empty.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Applies a binary operator to all elements of this collection and a start value, going right to left.
Applies a binary operator to all elements of this collection 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.
- Type Params
- B
the result type of the binary operator.
- Value Params
- op
the binary operator.
- z
the start value.
- Returns
the result of inserting
op
between consecutive elements of this collection, going right to left with the start valuez
on the right:op(x1, op(x2, ... op(xn, z)...))
wherex1, ..., xn
are the elements of this collection. Returnsz
if this collection is empty.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Tests whether a predicate holds for all elements of this collection.
Tests whether a predicate holds for all elements of this collection.
Note: may not terminate for infinite-sized collections.
- Value Params
- p
the predicate used to test elements.
- Returns
true
if this collection is empty or the given predicatep
holds for all elements of this collection, otherwisefalse
.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Apply f
to each element for its side effects
Note: [U] parameter needed to help scalac's type inference.
Apply f
to each element for its side effects
Note: [U] parameter needed to help scalac's type inference.
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Returns the value associated with a key, or a default value if the key is not contained in the map.
Returns the value associated with a key, or a default value if the key is not contained in the map.
- Type Params
- V1
the result type of the default computation.
- Value Params
- default
a computation that yields a default value in case no binding for
key
is found in the map.- key
the key.
- Returns
the value associated with
key
if it exists, otherwise the result of thedefault
computation.- Inherited from
- MapOps
- Source
- Map.scala
Partitions this iterable collection into a map of iterable collections according to some discriminator function.
Partitions this iterable collection into a map of iterable collections according to some discriminator function.
Note: Even when applied to a view or a lazy collection it will always force the elements.
- Type Params
- K
the type of keys returned by the discriminator function.
- Value Params
- f
the discriminator function.
- Returns
A map from keys to iterable 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 iterable collection of those elementsx
for whichf(x)
equalsk
.- Inherited from
- IterableOps
- Source
- Iterable.scala
Partitions this iterable collection into a map of iterable collections according to a discriminator function key
.
Partitions this iterable collection into a map of iterable collections according to a discriminator function key
.
Each element in a group is transformed into a value of type B
using the value
function.
It is equivalent to groupBy(key).mapValues(_.map(f))
, but more efficient.
case class User(name: String, age: Int)
def namesByAge(users: Seq[User]): Map[Int, Seq[String]] =
users.groupMap(_.age)(_.name)
Note: Even when applied to a view or a lazy collection it will always force the elements.
- Type Params
- B
the type of values returned by the transformation function
- K
the type of keys returned by the discriminator function
- Value Params
- f
the element transformation function
- key
the discriminator function
- Inherited from
- IterableOps
- Source
- Iterable.scala
Partitions this iterable collection into a map according to a discriminator function key
.
Partitions this iterable collection into a map according to a discriminator function key
. All the values that
have the same discriminator are then transformed by the f
function and then reduced into a
single value with the reduce
function.
It is equivalent to groupBy(key).mapValues(_.map(f).reduce(reduce))
, but more efficient.
def occurrences[A](as: Seq[A]): Map[A, Int] =
as.groupMapReduce(identity)(_ => 1)(_ + _)
Note: Even when applied to a view or a lazy collection it will always force the elements.
- Inherited from
- IterableOps
- Source
- Iterable.scala
Partitions elements in fixed size iterable collections.
Partitions elements in fixed size iterable collections.
- Value Params
- size
the number of elements per group
- Returns
An iterator producing iterable collections of size
size
, except the last will be less than sizesize
if the elements don't divide evenly.- See also
scala.collection.Iterator, method
grouped
- Inherited from
- IterableOps
- Source
- Iterable.scala
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.
- Returns
the first element of this iterable collection.
- Throws
- NoSuchElementException
if the iterable collection is empty.
- Inherited from
- IterableOps
- Source
- Iterable.scala
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.
- Returns
the first element of this iterable collection if it is nonempty,
None
if it is empty.- Inherited from
- IterableOps
- Source
- Iterable.scala
The initial part of the collection without its last element.
The initial part of the collection without its last element.
Note: Even when applied to a view or a lazy collection it will always force the elements.
- Inherited from
- IterableOps
- Source
- Iterable.scala
Iterates over the inits of this iterable collection.
Iterates over the inits of this iterable collection. The first value will be this
iterable collection and the final one will be an empty iterable collection, with the intervening
values the results of successive applications of init
.
Note: Even when applied to a view or a lazy collection it will always force the elements.
- Returns
an iterator over all the inits of this iterable collection
- Example
List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)
- Inherited from
- IterableOps
- Source
- Iterable.scala
Tests whether the collection is empty.
Tests whether the collection is empty.
Note: Implementations in subclasses that are not repeatedly traversable must take
care not to consume any elements when isEmpty
is called.
- Returns
true
if the collection contains no elements,false
otherwise.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Iterator can be used only once
Iterator can be used only once
- Inherited from
- IterableOnce
- Source
- IterableOnce.scala
- Returns
The number of elements in this collection, if it can be cheaply computed, -1 otherwise. Cheaply usually means: Not requiring a collection traversal.
- Inherited from
- IterableOnce
- Source
- IterableOnce.scala
Selects the last element.
Selects the last element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- Returns
The last element of this iterable collection.
- Throws
- NoSuchElementException
If the iterable collection is empty.
- Inherited from
- IterableOps
- Source
- Iterable.scala
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.
- Returns
the last element of this iterable collection$ if it is nonempty,
None
if it is empty.- Inherited from
- IterableOps
- Source
- Iterable.scala
Analogous to zip
except that the elements in each collection are not consumed until a strict operation is
invoked on the returned LazyZip2
decorator.
Analogous to zip
except that the elements in each collection are not consumed until a strict operation is
invoked on the returned LazyZip2
decorator.
Calls to lazyZip
can be chained to support higher arities (up to 4) without incurring the expense of
constructing and deconstructing intermediary tuples.
val xs = List(1, 2, 3)
val res = (xs lazyZip xs lazyZip xs lazyZip xs).map((a, b, c, d) => a + b + c + d)
// res == List(4, 8, 12)
- Type Params
- B
the type of the second element in each eventual pair
- Value Params
- that
the iterable providing the second element of each eventual pair
- Returns
a decorator
LazyZip2
that allows strict operations to be performed on the lazily evaluated pairs or chained calls tolazyZip
. Implicit conversion toIterable[(A, B)]
is also supported.- Inherited from
- Iterable
- Source
- Iterable.scala
Turns this partial function into a plain function returning an Option
result.
Turns this partial function into a plain function returning an Option
result.
- Returns
a function that takes an argument
x
toSome(this(x))
ifthis
is defined forx
, and toNone
otherwise.- See also
Function.unlift
- Inherited from
- PartialFunction
- Source
- PartialFunction.scala
Finds the largest element.
Finds the largest element.
Note: will not terminate for infinite-sized collections.
- Type Params
- B
The type over which the ordering is defined.
- Value Params
- ord
An ordering to be used for comparing elements.
- Returns
the largest element of this collection with respect to the ordering
ord
.- Throws
- UnsupportedOperationException
if this collection is empty.
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
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.
Note: will not terminate for infinite-sized collections.
- Type Params
- B
The result type of the function f.
- Value Params
- cmp
An ordering to be used for comparing elements.
- f
The measuring function.
- Returns
the first element of this collection with the largest value measured by function f with respect to the ordering
cmp
.- Throws
- UnsupportedOperationException
if this collection is empty.
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
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.
Note: will not terminate for infinite-sized collections.
- Type Params
- B
The result type of the function f.
- Value Params
- cmp
An ordering to be used for comparing elements.
- f
The measuring function.
- Returns
an option value containing the first element of this collection with the largest value measured by function f with respect to the ordering
cmp
.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Finds the largest element.
Finds the largest element.
Note: will not terminate for infinite-sized collections.
- Type Params
- B
The type over which the ordering is defined.
- Value Params
- ord
An ordering to be used for comparing elements.
- Returns
an option value containing the largest element of this collection with respect to the ordering
ord
.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Finds the smallest element.
Finds the smallest element.
Note: will not terminate for infinite-sized collections.
- Type Params
- B
The type over which the ordering is defined.
- Value Params
- ord
An ordering to be used for comparing elements.
- Returns
the smallest element of this collection with respect to the ordering
ord
.- Throws
- UnsupportedOperationException
if this collection is empty.
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
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.
Note: will not terminate for infinite-sized collections.
- Type Params
- B
The result type of the function f.
- Value Params
- cmp
An ordering to be used for comparing elements.
- f
The measuring function.
- Returns
the first element of this collection with the smallest value measured by function f with respect to the ordering
cmp
.- Throws
- UnsupportedOperationException
if this collection is empty.
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
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.
Note: will not terminate for infinite-sized collections.
- Type Params
- B
The result type of the function f.
- Value Params
- cmp
An ordering to be used for comparing elements.
- f
The measuring function.
- Returns
an option value containing the first element of this collection with the smallest value measured by function f with respect to the ordering
cmp
.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Finds the smallest element.
Finds the smallest element.
Note: will not terminate for infinite-sized collections.
- Type Params
- B
The type over which the ordering is defined.
- Value Params
- ord
An ordering to be used for comparing elements.
- Returns
an option value containing the smallest element of this collection with respect to the ordering
ord
.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Displays all elements of this collection in a string.
Displays all elements of this collection in a string.
Delegates to addString, which can be overridden.
- Returns
a string representation of this collection. In the resulting string the string representations (w.r.t. the method
toString
) of all elements of this collection follow each other without any separator string.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Displays all elements of this collection in a string using a separator string.
Displays all elements of this collection in a string using a separator string.
Delegates to addString, which can be overridden.
- Value Params
- sep
the separator string.
- Returns
a string representation of this collection. In the resulting string the string representations (w.r.t. the method
toString
) of all elements of this collection are separated by the stringsep
.- Example
List(1, 2, 3).mkString("|") = "1|2|3"
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Displays all elements of this collection in a string using start, end, and separator strings.
Displays all elements of this collection in a string using start, end, and separator strings.
Delegates to addString, which can be overridden.
- Value Params
- end
the ending string.
- sep
the separator string.
- start
the starting string.
- Returns
a string representation of this collection. The resulting string begins with the string
start
and ends with the stringend
. Inside, the string representations (w.r.t. the methodtoString
) of all elements of this collection are separated by the stringsep
.- Example
List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Tests whether the collection is not empty.
Tests whether the collection is not empty.
- Returns
true
if the collection contains at least one element,false
otherwise.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Composes this partial function with a fallback partial function which gets applied where this partial function is not defined.
Composes this partial function with a fallback partial function which gets applied where this partial function is not defined.
- Type Params
- A1
the argument type of the fallback function
- B1
the result type of the fallback function
- Value Params
- that
the fallback function
- Returns
a partial function which has as domain the union of the domains of this partial function and
that
. The resulting partial function takesx
tothis(x)
wherethis
is defined, and tothat(x)
where it is not.- Inherited from
- PartialFunction
- Source
- PartialFunction.scala
A pair of, first, all elements that satisfy predicate p
and, second,
all elements that do not.
A pair of, first, all elements that satisfy predicate p
and, second,
all elements that do not. Interesting because it splits a collection in two.
The default implementation provided here needs to traverse the collection twice.
Strict collections have an overridden version of partition
in StrictOptimizedIterableOps
,
which requires only a single traversal.
- Inherited from
- IterableOps
- Source
- Iterable.scala
Applies a function f
to each element of the iterable collection and returns a pair of iterable collections: the first one
made of those values returned by f
that were wrapped in scala.util.Left, and the second
one made of those wrapped in scala.util.Right.
Applies a function f
to each element of the iterable collection and returns a pair of iterable collections: the first one
made of those values returned by f
that were wrapped in scala.util.Left, and the second
one made of those wrapped in scala.util.Right.
Example:
val xs = Iterable(1, "one", 2, "two", 3, "three") partitionMap {
case i: Int => Left(i)
case s: String => Right(s)
}
// xs == (Iterable(1, 2, 3),
// Iterable(one, two, three))
- Type Params
- A1
the element type of the first resulting collection
- A2
the element type of the second resulting collection
- Value Params
- f
the 'split function' mapping the elements of this iterable collection to an scala.util.Either
- Returns
a pair of iterable collections: the first one made of those values returned by
f
that were wrapped in scala.util.Left, and the second one made of those wrapped in scala.util.Right.- Inherited from
- IterableOps
- Source
- Iterable.scala
Multiplies up the elements of this collection.
Multiplies up the elements of this collection.
Note: will not terminate for infinite-sized collections.
- Type Params
- B
the result type of the
*
operator.
- Value Params
- num
an implicit parameter defining a set of numeric operations which includes the
*
operator to be used in forming the product.
- Returns
the product of all elements of this collection with respect to the
*
operator innum
.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Reduces the elements of this collection using the specified associative binary operator.
Reduces the elements of this collection using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
- Type Params
- B
A type parameter for the binary operator, a supertype of
A
.
- Value Params
- op
A binary operator that must be associative.
- Returns
The result of applying reduce operator
op
between all the elements if the collection is nonempty.- Throws
- UnsupportedOperationException
if this collection is empty.
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Applies a binary operator to all elements of this collection, going left to right.
Applies a binary operator to all elements of this collection, 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.
- Type Params
- B
the result type of the binary operator.
- Value Params
- op
the binary operator.
- Returns
the result of inserting
op
between consecutive elements of this collection, going left to right:op( op( ... op(x1, x2) ..., xn-1), xn)
wherex1, ..., xn
are the elements of this collection.- Throws
- UnsupportedOperationException
if this collection is empty.
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Optionally applies a binary operator to all elements of this collection, going left to right.
Optionally applies a binary operator to all elements of this collection, 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.
- Type Params
- B
the result type of the binary operator.
- Value Params
- op
the binary operator.
- Returns
an option value containing the result of
reduceLeft(op)
if this collection is nonempty,None
otherwise.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Reduces the elements of this collection, if any, using the specified associative binary operator.
Reduces the elements of this collection, if any, using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
- Type Params
- B
A type parameter for the binary operator, a supertype of
A
.
- Value Params
- op
A binary operator that must be associative.
- Returns
An option value containing result of applying reduce operator
op
between all the elements if the collection is nonempty, andNone
otherwise.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Applies a binary operator to all elements of this collection, going right to left.
Applies a binary operator to all elements of this collection, 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.
- Type Params
- B
the result type of the binary operator.
- Value Params
- op
the binary operator.
- Returns
the result of inserting
op
between consecutive elements of this collection, going right to left:op(x1, op(x2, ..., op(xn-1, xn)...))
wherex1, ..., xn
are the elements of this collection.- Throws
- UnsupportedOperationException
if this collection is empty.
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Optionally applies a binary operator to all elements of this collection, going right to left.
Optionally applies a binary operator to all elements of this collection, 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.
- Type Params
- B
the result type of the binary operator.
- Value Params
- op
the binary operator.
- Returns
an option value containing the result of
reduceRight(op)
if this collection is nonempty,None
otherwise.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Creates a new immutable map from this immutable map by removing all elements of another collection.
Creates a new immutable map from this immutable map by removing all elements of another collection.
Note: Even when applied to a view or a lazy collection it will always force the elements.
Composes this partial function with an action function which gets applied to results of this partial function.
Composes this partial function with an action function which gets applied to results of this partial function. The action function is invoked only for its side effects; its result is ignored.
Note that expression pf.runWith(action)(x)
is equivalent to
if(pf isDefinedAt x) { action(pf(x)); true } else false
except that runWith
is implemented via applyOrElse
and thus potentially more efficient.
Using runWith
avoids double evaluation of pattern matchers and guards for partial function literals.
- Value Params
- action
the action function
- Returns
a function which maps arguments
x
toisDefinedAt(x)
. The resulting function runsaction(this(x))
wherethis
is defined.- See also
applyOrElse
.- Inherited from
- PartialFunction
- Source
- PartialFunction.scala
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.
- Type Params
- B
element type of the resulting collection
- Value Params
- op
the associative operator for the scan
- z
neutral element for the operator
op
- Returns
a new iterable collection containing the prefix scan of the elements in this iterable collection
- Inherited from
- IterableOps
- Source
- Iterable.scala
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.
Note: Even when applied to a view or a lazy collection it will always force the elements.
Example:
List(1, 2, 3, 4).scanRight(0)(_ + _) == List(10, 9, 7, 4, 0)
- Type Params
- B
the type of the elements in the resulting collection
- Value Params
- op
the binary operator applied to the intermediate result and the element
- z
the initial value
- Returns
collection with intermediate results
- Inherited from
- IterableOps
- Source
- Iterable.scala
The size of this collection.
The size of this collection.
Note: will not terminate for infinite-sized collections.
- Returns
the number of elements in this collection.
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Compares the size of this iterable collection to the size of another Iterable
.
Compares the size of this iterable collection to the size of another Iterable
.
- Value Params
- that
the
Iterable
whose size is compared with this iterable collection's size.
- Returns
A value
x
wherex < 0 if this.size < that.size x == 0 if this.size == that.size x > 0 if this.size > that.size
The method as implemented here does not call
size
directly; its running time isO(this.size min that.size)
instead ofO(this.size + that.size)
. The method should be overridden if computingsize
is cheap andknownSize
returns-1
.- Inherited from
- IterableOps
- Source
- Iterable.scala
Compares the size of this iterable collection to a test value.
Compares the size of this iterable collection to a test value.
- Value Params
- otherSize
the test value that gets compared with the size.
- Returns
A value
x
wherex < 0 if this.size < otherSize x == 0 if this.size == otherSize x > 0 if this.size > otherSize
The method as implemented here does not call
size
directly; its running time isO(size min otherSize)
instead ofO(size)
. The method should be overridden if computingsize
is cheap andknownSize
returns-1
.- See also
- Inherited from
- IterableOps
- Source
- Iterable.scala
Returns a value class containing operations for comparing the size of this iterable collection to a test value.
Returns a value class containing operations for comparing the size of this iterable collection to a test value.
These operations are implemented in terms of sizeCompare(Int)
, and
allow the following more readable usages:
this.sizeIs < size // this.sizeCompare(size) < 0
this.sizeIs <= size // this.sizeCompare(size) <= 0
this.sizeIs == size // this.sizeCompare(size) == 0
this.sizeIs != size // this.sizeCompare(size) != 0
this.sizeIs >= size // this.sizeCompare(size) >= 0
this.sizeIs > size // this.sizeCompare(size) > 0
- Inherited from
- IterableOps
- Source
- Iterable.scala
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 returned iterator will be empty when called on an empty collection. The last element the iterator produces may be smaller than the window size when the original collection isn't exhausted by the window before it and its last element isn't skipped by the step before it.
- Value Params
- size
the number of elements per group
- step
the distance between the first elements of successive groups
- Returns
An iterator producing iterable collections of size
size
, except the last element (which may be the only element) will be smaller if there are fewer thansize
elements remaining to be grouped.- See also
scala.collection.Iterator, method
sliding
- Example
List(1, 2, 3, 4, 5).sliding(2, 2) = Iterator(List(1, 2), List(3, 4), List(5))
List(1, 2, 3, 4, 5, 6).sliding(2, 3) = Iterator(List(1, 2), List(4, 5))
- Inherited from
- IterableOps
- Source
- Iterable.scala
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
.)
An empty collection returns an empty iterator, and a non-empty collection containing fewer elements than the window size returns an iterator that will produce the original collection as its only element.
- Value Params
- size
the number of elements per group
- Returns
An iterator producing iterable collections of size
size
, except for a non-empty collection with less thansize
elements, which returns an iterator that produces the source collection itself as its only element.- See also
scala.collection.Iterator, method
sliding
- Example
List().sliding(2) = empty iterator
List(1).sliding(2) = Iterator(List(1))
List(1, 2).sliding(2) = Iterator(List(1, 2))
List(1, 2, 3).sliding(2) = Iterator(List(1, 2), List(2, 3))
- Inherited from
- IterableOps
- Source
- Iterable.scala
Returns a scala.collection.Stepper for the elements of this collection.
Returns a scala.collection.Stepper for the elements of this collection.
The Stepper enables creating a Java stream to operate on the collection, see scala.jdk.StreamConverters. For collections holding primitive values, the Stepper can be used as an iterator which doesn't box the elements.
The implicit scala.collection.StepperShape parameter defines the resulting Stepper type according to the element type of this collection.
For collections of
Int
,Short
,Byte
orChar
, an scala.collection.IntStepper is returnedFor collections of
Double
orFloat
, a scala.collection.DoubleStepper is returnedFor collections of
Long
a scala.collection.LongStepper is returnedFor any other element type, an scala.collection.AnyStepper is returned
Note that this method is overridden in subclasses and the return type is refined to
S with EfficientSplit
, for example scala.collection.IndexedSeqOps.stepper. For Steppers marked with
scala.collection.Stepper.EfficientSplit, the converters in scala.jdk.StreamConverters
allow creating parallel streams, whereas bare Steppers can be converted only to sequential
streams.
- Inherited from
- IterableOnce
- Source
- IterableOnce.scala
Sums up the elements of this collection.
Sums up the elements of this collection.
Note: will not terminate for infinite-sized collections.
- Type Params
- B
the result type of the
+
operator.
- Value Params
- num
an implicit parameter defining a set of numeric operations which includes the
+
operator to be used in forming the sum.
- Returns
the sum of all elements of this collection with respect to the
+
operator innum
.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
The rest of the collection without its first element.
The rest of the collection without its first element.
- Inherited from
- IterableOps
- Source
- Iterable.scala
Iterates over the tails of this iterable collection.
Iterates over the tails of this iterable collection. The first value will be this
iterable collection and the final one will be an empty iterable collection, with the intervening
values the results of successive applications of tail
.
- Returns
an iterator over all the tails of this iterable collection
- Example
List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)
- Inherited from
- IterableOps
- Source
- Iterable.scala
Selects the last n elements.
Selects the last n elements.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- Value Params
- n
the number of elements to take from this iterable collection.
- Returns
a iterable collection consisting only of the last
n
elements of this iterable collection, or else the whole iterable collection, if it has less thann
elements. Ifn
is negative, returns an empty iterable collection.- Inherited from
- IterableOps
- Source
- Iterable.scala
Takes longest prefix of elements that satisfy a predicate.
Takes longest prefix of elements that satisfy a predicate.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- Value Params
- p
The predicate used to test elements.
- Returns
the longest prefix of this iterable collection whose elements all satisfy the predicate
p
.- Inherited from
- IterableOps
- Source
- Iterable.scala
Given a collection factory factory
, convert this collection to the appropriate
representation for the current element type A
.
Given a collection factory factory
, convert this collection to the appropriate
representation for the current element type A
. Example uses:
xs.to(List) xs.to(ArrayBuffer) xs.to(BitSet) // for xs: Iterable[Int]
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Convert collection to array.
Convert collection to array.
Implementation note: DO NOT call Array.from from this method.
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
- Returns
This collection as a
Seq[A]
. This is equivalent toto(Seq)
but might be faster.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Transposes this iterable collection of iterable collections into a iterable collection of iterable collections.
Transposes this iterable collection of iterable collections into a iterable collection of iterable collections.
The resulting collection's type will be guided by the static type of iterable collection. For example:
val xs = List(
Set(1, 2, 3),
Set(4, 5, 6)).transpose
// xs == List(
// List(1, 4),
// List(2, 5),
// List(3, 6))
val ys = Vector(
List(1, 2, 3),
List(4, 5, 6)).transpose
// ys == Vector(
// Vector(1, 4),
// Vector(2, 5),
// Vector(3, 6))
Note: Even when applied to a view or a lazy collection it will always force the elements.
- Type Params
- B
the type of the elements of each iterable collection.
- Value Params
- asIterable
an implicit conversion which asserts that the element type of this iterable collection is an
Iterable
.
- Returns
a two-dimensional iterable collection of iterable collections which has as nth row the nth column of this iterable collection.
- Throws
- IllegalArgumentException
if all collections in this iterable collection are not of the same size.
- Inherited from
- IterableOps
- Source
- Iterable.scala
Tries to extract a B
from an A
in a pattern matching expression.
Tries to extract a B
from an A
in a pattern matching expression.
- Inherited from
- PartialFunction
- Source
- PartialFunction.scala
Converts this iterable collection of pairs into two collections of the first and second half of each pair.
Converts this iterable collection of pairs into two collections of the first and second half of each pair.
val xs = Iterable(
(1, "one"),
(2, "two"),
(3, "three")).unzip
// xs == (Iterable(1, 2, 3),
// Iterable(one, two, three))
- Type Params
- A1
the type of the first half of the element pairs
- A2
the type of the second half of the element pairs
- Value Params
- asPair
an implicit conversion which asserts that the element type of this iterable collection is a pair.
- Returns
a pair of iterable collections, containing the first, respectively second half of each element pair of this iterable collection.
- Inherited from
- IterableOps
- Source
- Iterable.scala
Converts this iterable collection of triples into three collections of the first, second, and third element of each triple.
Converts this iterable collection of triples into three collections of the first, second, and third element of each triple.
val xs = Iterable(
(1, "one", '1'),
(2, "two", '2'),
(3, "three", '3')).unzip3
// xs == (Iterable(1, 2, 3),
// Iterable(one, two, three),
// Iterable(1, 2, 3))
- Type Params
- A1
the type of the first member of the element triples
- A2
the type of the second member of the element triples
- A3
the type of the third member of the element triples
- Value Params
- asTriple
an implicit conversion which asserts that the element type of this iterable collection is a triple.
- Returns
a triple of iterable collections, containing the first, second, respectively third member of each element triple of this iterable collection.
- Inherited from
- IterableOps
- Source
- Iterable.scala
Update a mapping for the specified key and its current optionally-mapped value
(Some
if there is current mapping, None
if not).
Update a mapping for the specified key and its current optionally-mapped value
(Some
if there is current mapping, None
if not).
If the remapping function returns Some(v)
, the mapping is updated with the new value v
.
If the remapping function returns None
, the mapping is removed (or remains absent if initially absent).
If the function itself throws an exception, the exception is rethrown, and the current mapping is left unchanged.
The same map with a given default function.
The same map with a given default function.
Note: The default is only used for apply
. Other methods like get
, contains
, iterator
, keys
, etc.
are not affected by withDefault
.
Invoking transformer methods (e.g. map
) will not preserve the default value.
The same map with a given default value.
The same map with a given default value.
Note: The default is only used for apply
. Other methods like get
, contains
, iterator
, keys
, etc.
are not affected by withDefaultValue
.
Invoking transformer methods (e.g. map
) will not preserve the default value.
- Definition Classes
- Inherited from
- MapFactoryDefaults
- Source
- Iterable.scala
Returns a iterable collection formed from this iterable collection and another iterable collection by combining corresponding elements in pairs.
Returns a iterable collection formed from this iterable collection 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.
- Type Params
- B
the type of the second half of the returned pairs
- Value Params
- that
The iterable providing the second half of each result pair
- Returns
a new iterable collection containing pairs consisting of corresponding elements of this iterable collection and
that
. The length of the returned collection is the minimum of the lengths of this iterable collection andthat
.- Inherited from
- IterableOps
- Source
- Iterable.scala
Returns a iterable collection formed from this iterable collection and another iterable collection by combining corresponding elements in pairs.
Returns a iterable collection formed from this iterable collection 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.
- Value Params
- that
the iterable providing the second half of each result pair
- thatElem
the element to be used to fill up the result if
that
is shorter than this iterable collection.- thisElem
the element to be used to fill up the result if this iterable collection is shorter than
that
.
- Returns
a new collection of type
That
containing pairs consisting of corresponding elements of this iterable collection andthat
. The length of the returned collection is the maximum of the lengths of this iterable collection andthat
. If this iterable collection is shorter thanthat
,thisElem
values are used to pad the result. Ifthat
is shorter than this iterable collection,thatElem
values are used to pad the result.- Inherited from
- IterableOps
- Source
- Iterable.scala
Deprecated and Inherited methods
- Deprecated
- Inherited from
- IterableOps
- Source
- Iterable.scala
- Deprecated
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
- Deprecated
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
- Deprecated
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
- Deprecated
- Inherited from
- IterableOps
- Source
- Iterable.scala
- Deprecated
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Filters this map by retaining only keys satisfying a predicate.
Filters this map by retaining only keys satisfying a predicate.
Tests whether this collection is known to have a finite size.
Tests whether this 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. Non-empty Iterators usually return
false
even if they were created from a collection with a known
finite size.
Note: many collection methods will not work on collections of infinite sizes.
The typical failure mode is an infinite loop. These methods always attempt a
traversal without checking first that hasDefiniteSize
returns true
.
However, checking hasDefiniteSize
can provide an assurance that size is
well-defined and non-termination is not a concern.
- Returns
true
if this collection is known to have finite size,false
otherwise.- See also
method
knownSize
for a more useful alternative- Deprecated
This method is deprecated in 2.13 because it does not provide any actionable information. As noted above, even the collection library itself does not use it. When there is no guarantee that a collection is finite, it is generally best to attempt a computation anyway and document that it will not terminate for infinite collections rather than backing out because this would prevent performing the computation on collections that are in fact finite even though
hasDefiniteSize
returnsfalse
.- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Transforms this map by applying a function to every retrieved value.
Transforms this map by applying a function to every retrieved value.
- Deprecated
- Inherited from
- IterableOps
- Source
- Iterable.scala
- Deprecated
- Inherited from
- Iterable
- Source
- Iterable.scala
- Deprecated
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
- Deprecated
- Inherited from
- IterableOnceOps
- Source
- IterableOnce.scala
Converts this iterable collection to an unspecified Iterable.
Converts this iterable collection to an unspecified Iterable. Will return the same collection if this instance is already Iterable.
- Returns
An Iterable containing all elements of this iterable collection.
- Deprecated
- Inherited from
- IterableOps
- Source
- Iterable.scala
A view over a slice of the elements of this collection.
A view over a slice of the elements of this collection.
- Deprecated
- Inherited from
- IterableOps
- Source
- Iterable.scala