We need a whole WithFilter class to honor the "doesn't create a new collection" contract even though it seems unlikely to matter much in a collection with max size 1.
A method that should be called from every well-designed equals method that is open to be overridden in a subclass.
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
Returns the option's value.
Returns the option's value.
if the option is empty.
The option must be nonEmpty.
Returns true if the option is None, false otherwise.
The size of this product.
The nth element of this product, 0-based.
The nth element of this product, 0-based. In other words, for a
product A(x1, ..., xk), returns x(n+1) where 0 < n < k.
the index of the element to return
the element n elements after the first element
Test two objects for inequality.
Test two objects for inequality.
true if !(this == that), false otherwise.
Equivalent to x.hashCode except for boxed numeric types and null.
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 ==
[use case] Returns a new option containing the elements from the left hand operand followed by the elements from the right hand operand.
Returns a new option containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the option is the most specific superclass encompassing the element types of the two operands.
Example:
scala> val a = LinkedList(1) a: scala.collection.mutable.LinkedList[Int] = LinkedList(1) scala> val b = LinkedList(2) b: scala.collection.mutable.LinkedList[Int] = LinkedList(2) scala> val c = a ++ b c: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2) scala> val d = LinkedList('a') d: scala.collection.mutable.LinkedList[Char] = LinkedList(a) scala> val e = c ++ d e: scala.collection.mutable.LinkedList[AnyVal] = LinkedList(1, 2, a)
the element type of the returned collection.
the traversable to append.
a new option which contains all elements of this option
followed by all elements of that.
As with ++, returns a new collection containing the elements from the
left operand followed by the elements from the right operand.
As with ++, returns a new collection containing the elements from the
left operand followed by the elements from the right operand.
It differs from ++ in that the right operand determines the type of
the resulting collection rather than the left one.
Mnemonic: the COLon is on the side of the new COLlection type.
Example:
scala> val x = List(1) x: List[Int] = List(1) scala> val y = LinkedList(2) y: scala.collection.mutable.LinkedList[Int] = LinkedList(2) scala> val z = x ++: y z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)
This overload exists because: for the implementation of ++: we should
reuse that of ++ because many collections override it with more
efficient versions.
Since TraversableOnce has no ++ method, we have to implement that
directly, but Traversable and down can use the overload.
the element type of the returned collection.
the class of the returned collection. Where possible, That is
the same class as the current collection class Repr, but this
depends on the element type B being admissible for that class,
which means that an implicit instance of type CanBuildFrom[Repr, B, That]
is found.
the traversable to append.
an implicit value of class CanBuildFrom which determines
the result class That from the current representation type Repr and
and the new element type B.
a new collection of type That which contains all elements
of this iterable collection followed by all elements of that.
[use case] As with ++, returns a new collection containing the elements from the left operand followed by the
elements from the right operand.
As with ++, returns a new collection containing the elements from the left operand followed by the
elements from the right operand.
It differs from ++ in that the right operand determines the type of
the resulting collection rather than the left one.
Mnemonic: the COLon is on the side of the new COLlection type.
Example:
scala> val x = List(1) x: List[Int] = List(1) scala> val y = LinkedList(2) y: scala.collection.mutable.LinkedList[Int] = LinkedList(2) scala> val z = x ++: y z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)
the element type of the returned collection.
the traversable to append.
a new option which contains all elements of this option
followed by all elements of that.
Applies a binary operator to a start value and all elements of this iterable collection, going left to right.
Applies a binary operator to a start value and all elements of this iterable collection, 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 = LinkedList(1,2,3,4) a: scala.collection.mutable.LinkedList[Int] = LinkedList(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 iterable collection,
going left to right with the start value z on the left:
op(...op(op(z, x_1), x_2), ..., x_n)
where x1, ..., xn are the elements of this iterable collection.
Applies a binary operator to all elements of this iterable collection and a start value, going right to left.
Applies a binary operator to all elements of this iterable collection 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 = LinkedList(1,2,3,4) a: scala.collection.mutable.LinkedList[Int] = LinkedList(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 iterable collection,
going right to left with the start value z on the right:
op(x_1, op(x_2, ... op(x_n, z)...))
where x1, ..., xn are the elements of this iterable collection.
Test two objects for equality.
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.
Appends all elements of this iterable collection to a string builder.
Appends all elements of this iterable collection to a string builder.
The written text consists of the string representations (w.r.t. the method
toString) of all elements of this iterable collection without any separator string.
Example:
scala> val a = LinkedList(1,2,3,4) a: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4) scala> val b = new StringBuilder() b: StringBuilder = scala> val h = a.addString(b) b: StringBuilder = 1234
the string builder to which elements are appended.
the string builder b to which elements were appended.
Appends all elements of this iterable collection to a string builder using a separator string.
Appends all elements of this iterable 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 iterable collection, separated by the string sep.
Example:
scala> val a = LinkedList(1,2,3,4) a: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4) scala> val b = new StringBuilder() b: StringBuilder = scala> a.addString(b, ", ") res0: StringBuilder = 1, 2, 3, 4
the string builder to which elements are appended.
the separator string.
the string builder b to which elements were appended.
Appends all elements of this iterable collection to a string builder using start, end, and separator strings.
Appends all elements of this iterable collection to a string builder using start, end, and separator strings.
The written text begins with the string start and ends with the string end.
Inside, the string representations (w.r.t. the method toString)
of all elements of this iterable collection are separated by the string sep.
Example:
scala> val a = LinkedList(1,2,3,4) a: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4) scala> val b = new StringBuilder() b: StringBuilder = scala> a.addString(b, "LinkedList(", ", ", ")") res1: StringBuilder = LinkedList(1, 2, 3, 4)
the string builder to which elements are appended.
the starting string.
the separator string.
the ending string.
the string builder b to which elements were appended.
Aggregates the results of applying an operator to subsequent elements.
Aggregates the results of applying an operator to subsequent elements.
This is a more general form of fold and reduce. It has similar
semantics, but does not require the result to be a supertype of the
element type. It traverses the elements in different partitions
sequentially, using seqop to update the result, and then applies
combop to results from different partitions. The implementation of
this operation may operate on an arbitrary number of collection
partitions, so combop may be invoked an arbitrary number of times.
For example, one might want to process some elements and then produce
a Set. In this case, seqop would process an element and append it
to the list, while combop would concatenate two lists from different
partitions together. The initial value z would be an empty set.
pc.aggregate(Set[Int]())(_ += process(_), _ ++ _)
Another example is calculating geometric mean from a collection of doubles (one would typically require big doubles for this).
the type of accumulated results
the initial value for the accumulated result of the partition - this
will typically be the neutral element for the seqop operator (e.g.
Nil for list concatenation or 0 for summation)
an operator used to accumulate results within a partition
an associative operator used to combine results from different partitions
Cast the receiver object to be of type T0.
Cast the receiver object to be of type T0.
Note that the success of a cast at runtime is modulo Scala's erasure semantics.
Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at
runtime, while the expression List(1).asInstanceOf[List[String]] will not.
In the latter example, because the type argument is erased as part of compilation it is
not possible to check whether the contents of the list are of the requested type.
the receiver object.
if the receiver object is not an instance of the erasure of type T0.
Create a copy of the receiver object.
Returns a scala.Some containing the result of
applying pf to this scala.Option's contained
value, if this option is
nonempty and pf is defined for that value.
Returns a scala.Some containing the result of
applying pf to this scala.Option's contained
value, if this option is
nonempty and pf is defined for that value.
Returns None otherwise.
the partial function.
the result of applying pf to this scala.Option's
value (if possible), or None.
Finds the first element of the iterable collection for which the given partial function is defined, and applies the partial function to it.
Finds the first element of the iterable 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.
the partial function
an option value containing pf applied to the first
value for which it is defined, or None if none exists.
Seq("a", 1, 5L).collectFirst({ case x: Int => x*10 }) = Some(10)
The factory companion object that builds instances of class Iterable.
The factory companion object that builds instances of class Iterable.
(or its Iterable superclass where class Iterable is not a Seq.)
[use case] Copies elements of this option to an array.
Copies elements of this option to an array.
Fills the given array xs with at most len elements of
this option, starting at position start.
Copying will stop once either the end of the current option is reached,
or the end of the array is reached, or len elements have been copied.
the array to fill.
the starting index.
the maximal number of elements to copy.
[use case] Copies values of this option to an array.
Copies values of this option to an array.
Fills the given array xs with values of this option.
Copying will stop once either the end of the current option is reached,
or the end of the array is reached.
the array to fill.
[use case] Copies values of this option to an array.
Copies values of this option to an array.
Fills the given array xs with values of this option, beginning at index start.
Copying will stop once either the end of the current option is reached,
or the end of the array is reached.
the array to fill.
the starting index.
Copies all elements of this iterable collection to a buffer.
Copies all elements of this iterable collection to a buffer.
Note: will not terminate for infinite-sized collections.
The buffer to which elements are copied.
Counts the number of elements in the iterable collection which satisfy a predicate.
Counts the number of elements in the iterable collection which satisfy a predicate.
the predicate used to test elements.
the number of elements satisfying the predicate p.
Selects all elements except first n ones.
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 iterable collection.
a iterable collection consisting of all elements of this iterable collection except the first n ones, or else the
empty iterable collection, if this iterable collection has less than n elements.
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.
The number of elements to take
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 than n elements.
Drops longest prefix of elements that satisfy a predicate.
Drops longest prefix of elements that satisfy a predicate.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the longest suffix of this iterable collection whose first element
does not satisfy the predicate p.
Tests whether the argument (arg0) is a reference to the receiver object (this).
Tests whether the argument (arg0) is a reference to the receiver object (this).
The eq method implements an equivalence relation on
non-null instances of AnyRef, and has three additional properties:
x and y of type AnyRef, multiple invocations of
x.eq(y) consistently returns true or consistently returns false.x of type AnyRef, x.eq(null) and null.eq(x) returns false.null.eq(null) returns true. When overriding the equals or hashCode methods, it is important to ensure that their behavior is
consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they
should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).
true if the argument is a reference to the receiver object; false otherwise.
The equality method for reference types.
Returns true if this option is nonempty and the predicate
p returns true when applied to this scala.Option's value.
Returns true if this option is nonempty and the predicate
p returns true when applied to this scala.Option's value.
Otherwise, returns false.
the predicate to test
Returns this scala.Option if it is nonempty and applying the predicate p to
this scala.Option's value returns true.
Returns this scala.Option if it is nonempty and applying the predicate p to
this scala.Option's value returns true. Otherwise, return None.
the predicate used for testing.
Returns this scala.Option if it is nonempty and applying the predicate p to
this scala.Option's value returns false.
Returns this scala.Option if it is nonempty and applying the predicate p to
this scala.Option's value returns false. Otherwise, return None.
the predicate used for testing.
Called by the garbage collector on the receiver object when there are no more references to the object.
Called by the garbage collector on the receiver object when there are no more references to the object.
The details of when and if the finalize method is invoked, as
well as the interaction between finalize and non-local returns
and exceptions, are all platform dependent.
Finds the first element of the iterable collection satisfying a predicate, if any.
Finds the first element of the iterable 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.
the predicate used to test elements.
an option value containing the first element in the iterable collection
that satisfies p, or None if none exists.
Returns the result of applying f to this scala.Option's value if
this scala.Option is nonempty.
Returns the result of applying f to this scala.Option's value if
this scala.Option is nonempty.
Returns None if this scala.Option is empty.
Slightly different from map in that f is expected to
return an scala.Option (which could be None).
the function to apply
foreach
map
Returns the result of applying f to this scala.Option's
value if the scala.Option is nonempty.
Returns the result of applying f to this scala.Option's
value if the scala.Option is nonempty. Otherwise, evaluates
expression ifEmpty.
the expression to evaluate if empty.
the function to apply if nonempty.
This is equivalent to scala.Option map f getOrElse ifEmpty.
Applies a binary operator to a start value and all elements of this iterable collection, going left to right.
Applies a binary operator to a start value and all elements of this iterable 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.
the result type of the binary operator.
the start value.
the binary operator.
the result of inserting op between consecutive elements of this iterable collection,
going left to right with the start value z on the left:
op(...op(z, x_1), x_2, ..., x_n)
where x1, ..., xn are the elements of this iterable collection.
Applies a binary operator to all elements of this iterable collection and a start value, going right to left.
Applies a binary operator to all elements of this iterable 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.
the result type of the binary operator.
the start value.
the binary operator.
the result of inserting op between consecutive elements of this iterable collection,
going right to left with the start value z on the right:
op(x_1, op(x_2, ... op(x_n, z)...))
where x1, ..., xn are the elements of this iterable collection.
Returns true if this option is empty or the predicate
p returns true when applied to this scala.Option's value.
Returns true if this option is empty or the predicate
p returns true when applied to this scala.Option's value.
the predicate to test
Apply the given procedure f to the option's value,
if it is nonempty.
Apply the given procedure f to the option's value,
if it is nonempty. Otherwise, do nothing.
the procedure to apply.
flatMap
map
Returns string formatted according to given format string.
Returns string formatted according to given format string.
Format strings are as for String.format
(@see java.lang.String.format).
The generic builder that builds instances of Iterable at arbitrary element types.
The generic builder that builds instances of Iterable at arbitrary element types.
A representation that corresponds to the dynamic class of the receiver object.
A representation that corresponds to the dynamic class of the receiver object.
The nature of the representation is platform dependent.
a representation that corresponds to the dynamic class of the receiver object.
not specified by SLS as a member of AnyRef
Returns the option's value if the option is nonempty, otherwise
return the result of evaluating default.
Returns the option's value if the option is nonempty, otherwise
return the result of evaluating default.
the default expression.
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: 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 iterable collection.
the type of keys returned by the discriminator function.
the discriminator function.
A map from keys to iterable collections such that the following invariant holds:
(xs partition f)(k) = xs filter (x => f(x) == k) That is, every key k is bound to a iterable collection of those elements x
for which f(x) equals k.
Partitions elements in fixed size iterable collections.
Partitions elements in fixed size iterable collections.
the number of elements per group
An iterator producing iterable collections of size size, except the
last will be truncated if the elements don't divide evenly.
scala.collection.Iterator, method grouped
Tests whether this iterable collection is known to have a finite size.
Tests whether this iterable collection is known to have a finite size.
All strict collections are known to have finite size. For a non-strict
collection such as Stream, the predicate returns true if all
elements have been computed. It returns false if the stream is
not yet evaluated to the end.
Note: many collection methods will not work on collections of infinite sizes.
true if this collection is known to have finite size,
false otherwise.
The hashCode method for reference types.
Selects the first element of this iterable collection.
Selects the first element of this iterable collection.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the first element of this iterable collection.
if the iterable collection is empty.
Optionally selects the first element.
Optionally selects the first element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the first element of this iterable collection if it is nonempty,
None if it is empty.
Selects all elements except the last.
Selects all elements except the last.
Note: might return different results for different runs, unless the underlying collection type is ordered.
a iterable collection consisting of all elements of this iterable collection except the last one.
if the iterable collection is empty.
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.
an iterator over all the inits of this iterable collection
List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)
Returns true if the option is an instance of scala.Some, false otherwise.
Test whether the dynamic type of the receiver object is T0.
Test whether the dynamic type of the receiver object is T0.
Note that the result of the test is modulo Scala's erasure semantics.
Therefore the expression 1.isInstanceOf[String] will return false, while the
expression List(1).isInstanceOf[List[String]] will return true.
In the latter example, because the type argument is erased as part of compilation it is
not possible to check whether the contents of the list are of the specified type.
true if the receiver object is an instance of erasure of type T0; false otherwise.
Tests whether this iterable collection can be repeatedly traversed.
Tests whether this iterable collection can be repeatedly traversed.
true
Returns a singleton iterator returning the scala.Option's value if it is nonempty, or an empty iterator if the option is empty.
Selects the last element.
Selects the last element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
The last element of this iterable collection.
If the iterable collection is empty.
Optionally selects the last element.
Optionally selects the last element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the last element of this iterable collection$ if it is nonempty,
None if it is empty.
Returns a scala.Some containing the result of applying f to this scala.Option's
value if this scala.Option is nonempty.
Returns a scala.Some containing the result of applying f to this scala.Option's
value if this scala.Option is nonempty.
Otherwise return None.
the function to apply
This is similar to flatMap except here,
f does not need to wrap its result in an scala.Option.
foreach
flatMap
[use case] Finds the largest element.
Finds the largest element.
the largest element of this option.
[use case] Finds the smallest element.
Finds the smallest element.
the smallest element of this option
Displays all elements of this iterable collection in a string.
Displays all elements of this iterable collection in a string.
a string representation of this iterable collection. In the resulting string
the string representations (w.r.t. the method toString)
of all elements of this iterable collection follow each other without any
separator string.
Displays all elements of this iterable collection in a string using a separator string.
Displays all elements of this iterable collection in a string using a separator string.
the separator string.
a string representation of this iterable collection. In the resulting string
the string representations (w.r.t. the method toString)
of all elements of this iterable collection are separated by the string sep.
List(1, 2, 3).mkString("|") = "1|2|3"
Displays all elements of this iterable collection in a string using start, end, and separator strings.
Displays all elements of this iterable collection in a string using start, end, and separator strings.
the starting string.
the separator string.
the ending string.
a string representation of this iterable collection. 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 iterable collection are separated by
the string sep.
List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"
Equivalent to !(this eq that).
Equivalent to !(this eq that).
true if the argument is not a reference to the receiver object; false otherwise.
Returns false if the option is None, true otherwise.
Returns false if the option is None, true otherwise.
Implemented here to avoid the implicit conversion to Iterable.
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up a single thread that is waiting on the receiver object's monitor.
not specified by SLS as a member of AnyRef
Wakes up all threads that are waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.
not specified by SLS as a member of AnyRef
Returns this scala.Option if it is nonempty,
otherwise return the result of evaluating alternative.
Returns this scala.Option if it is nonempty,
otherwise return the result of evaluating alternative.
the alternative expression.
Returns the option's value if it is nonempty,
or null if it is empty.
Returns the option's value if it is nonempty,
or null if it is empty.
Although the use of null is discouraged, code written to use
scala.Option must often interface with code that expects and returns nulls.
val initalText: Option[String] = getInitialText val textField = new JComponent(initalText.orNull,20)
Returns a parallel implementation of this collection.
Returns a parallel implementation of this collection.
For most collection types, this method creates a new parallel collection by copying
all the elements. For these collection, par takes linear time. Mutable collections
in this category do not produce a mutable parallel collection that has the same
underlying dataset, so changes in one collection will not be reflected in the other one.
Specific collections (e.g. ParArray or mutable.ParHashMap) override this default
behaviour by creating a parallel collection which shares the same underlying dataset.
For these collections, par takes constant or sublinear time.
All parallel collections return a reference to themselves.
a parallel implementation of this collection
Partitions this iterable collection in two iterable collections according to a predicate.
Partitions this iterable collection in two iterable collections according to a predicate.
the predicate on which to partition.
a pair of iterable collections: the first iterable collection consists of all elements that
satisfy the predicate p and the second iterable collection consists of all elements
that don't. The relative order of the elements in the resulting iterable collections
is the same as in the original iterable collection.
[use case] Multiplies up the elements of this collection.
Multiplies up the elements of this collection.
the product of all elements in this option 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 option and as result type of product.
Examples of such types are: Long, Float, Double, BigInt.
An iterator over all the elements of this product.
An iterator over all the elements of this product.
in the default implementation, an Iterator[Any]
A string used in the toString methods of derived classes.
A string used in the toString methods of derived classes.
Implementations may override this method to prepend a string prefix
to the result of toString methods.
in the default implementation, the empty string
Reduces the elements of this iterable collection using the specified associative binary operator.
Reduces the elements of this iterable collection 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 iterable collection is nonempty.
if this iterable collection is empty.
Applies a binary operator to all elements of this iterable collection, going left to right.
Applies a binary operator to all elements of this iterable 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.
the result type of the binary operator.
the binary operator.
the result of inserting op between consecutive elements of this iterable collection,
going left to right:
op( op( ... op(x_1, x_2) ..., x_{n-1}), x_n) where x1, ..., xn are the elements of this iterable collection.
if this iterable collection is empty.
Optionally applies a binary operator to all elements of this iterable collection, going left to right.
Optionally applies a binary operator to all elements of this iterable 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.
the result type of the binary operator.
the binary operator.
an option value containing the result of reduceLeft(op) is this iterable collection is nonempty,
None otherwise.
Reduces the elements of this iterable collection, if any, using the specified associative binary operator.
Reduces the elements of this iterable collection, 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 iterable collection, going right to left.
Applies a binary operator to all elements of this iterable 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.
the result type of the binary operator.
the binary operator.
the result of inserting op between consecutive elements of this iterable collection,
going right to left:
op(x_1, op(x_2, ..., op(x_{n-1}, x_n)...)) where x1, ..., xn are the elements of this iterable collection.
if this iterable collection is empty.
Optionally applies a binary operator to all elements of this iterable collection, going right to left.
Optionally applies a binary operator to all elements of this iterable 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.
the result type of the binary operator.
the binary operator.
an option value containing the result of reduceRight(op) is this iterable collection is nonempty,
None otherwise.
The collection of type iterable collection underlying this TraversableLike object.
The collection of type iterable collection underlying this TraversableLike object.
By default this is implemented as the TraversableLike object itself,
but this can be overridden.
[use case] Checks if the other iterable collection contains the same elements in the same order as this option.
Checks if the other iterable collection contains the same elements in the same order as this option.
the collection to compare with.
true, if both collections contain the same elements in the same order, false otherwise.
Computes a prefix scan of the elements of the collection.
Computes a prefix scan of the elements of the collection.
Note: The neutral element z may be applied more than once.
element type of the resulting collection
type of the resulting collection
neutral element for the operator op
the associative operator for the scan
combiner factory which provides a combiner
a new iterable collection containing the prefix scan of the elements in this iterable collection
Produces a collection containing cumulative results of applying the operator going left to right.
Produces a collection containing cumulative results of applying the operator going left to right.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the type of the elements in the resulting collection
the actual type of the resulting collection
the initial value
the binary operator applied to the intermediate result and the element
an implicit value of class CanBuildFrom which determines
the result class That from the current representation type Repr and
and the new element type B.
collection with intermediate results
Produces a collection containing cumulative results of applying the operator going right to left.
Produces a collection containing cumulative results of applying the operator going right to left. The head of the collection is the last cumulative result.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
Example:
List(1, 2, 3, 4).scanRight(0)(_ + _) == List(10, 9, 7, 4, 0)
the type of the elements in the resulting collection
the actual type of the resulting collection
the initial value
the binary operator applied to the intermediate result and the element
an implicit value of class CanBuildFrom which determines
the result class That from the current representation type Repr and
and the new element type B.
collection with intermediate results
(Changed in version 2.9.0) The behavior of scanRight has changed. The previous behavior can be reproduced with scanRight.reverse.
A version of this collection with all of the operations implemented sequentially (i.
A version of this collection with all of the operations implemented sequentially (i.e. in a single-threaded manner).
This method returns a reference to this collection. In parallel collections, it is redefined to return a sequential implementation of this collection. In both cases, it has O(1) complexity.
a sequential view of the collection.
The size of this iterable collection.
The size of this iterable collection.
Note: will not terminate for infinite-sized collections.
the number of elements in this iterable collection.
Selects an interval of elements.
Selects an interval of elements. The returned collection is made up
of all elements x which satisfy the invariant:
from <= indexOf(x) < until
Note: might return different results for different runs, unless the underlying collection type is ordered.
a iterable collection containing the elements greater than or equal to
index from extending up to (but not including) index until
of this iterable collection.
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)
the number of elements per group
the distance between the first elements of successive groups (defaults to 1)
An iterator producing iterable collections of size size, except the
last and the only element will be truncated if there are
fewer elements than size.
scala.collection.Iterator, method sliding
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)
the number of elements per group
An iterator producing iterable collections of size size, except the
last and the only element will be truncated if there are
fewer elements than size.
scala.collection.Iterator, method sliding
Splits this iterable collection into a prefix/suffix pair according to a predicate.
Splits this iterable 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.
a pair consisting of the longest prefix of this iterable collection whose
elements all satisfy p, and the rest of this iterable collection.
Splits this iterable collection into two at a given position.
Splits this iterable 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 iterable collections consisting of the first n
elements of this iterable collection, and the other elements.
Defines the prefix of this object's toString representation.
Defines the prefix of this object's toString representation.
a string representation which starts the result of toString
applied to this iterable collection. By default the string prefix is the
simple name of the collection class iterable collection.
[use case] Sums up the elements of this collection.
Sums up the elements of this collection.
the sum of all elements in this option 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 option and as result type of sum.
Examples of such types are: Long, Float, Double, BigInt.
Selects all elements except the first.
Selects all elements except the first.
Note: might return different results for different runs, unless the underlying collection type is ordered.
a iterable collection consisting of all elements of this iterable collection except the first one.
if the iterable collection is empty.
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.
an iterator over all the tails of this iterable collection
List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)
Selects first n elements.
Selects first n elements.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the number of elements to take from this iterable collection.
a iterable collection consisting only of the first n elements of this iterable collection,
or else the whole iterable collection, if it has less than n elements.
Selects last n elements.
Selects last n elements.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the number of elements to take
a iterable collection consisting only of the last n elements of this iterable collection, or else the
whole iterable collection, if it has less than n elements.
Takes longest prefix of elements that satisfy a predicate.
Takes longest prefix of elements that satisfy a predicate.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the longest prefix of this iterable collection whose elements all satisfy
the predicate p.
[use case] Converts this option into another by copying all elements.
Converts this option into another by copying all elements.
The collection type to build.
a new collection containing all elements of this option.
[use case] Converts this option to an array.
Converts this option to an array.
an array containing all elements of this option.
An ClassTag must be available for the element type of this option.
Converts this iterable collection to a mutable buffer.
Converts this iterable collection to a mutable buffer.
Note: will not terminate for infinite-sized collections.
a buffer containing all elements of this iterable collection.
Converts this iterable collection to an indexed sequence.
Converts this iterable collection to an indexed sequence.
Note: will not terminate for infinite-sized collections.
an indexed sequence containing all elements of this iterable collection.
Converts this iterable collection to an iterable collection.
Converts this iterable collection 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 iterable collection.
Returns an Iterator over the elements in this iterable collection.
Returns an Iterator over the elements in this iterable collection. 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 iterable collection.
Returns a scala.util.Right containing the given
argument right if this is empty, or
a scala.util.Left containing this scala.Option's value
if this scala.Option is nonempty.
Returns a scala.util.Right containing the given
argument right if this is empty, or
a scala.util.Left containing this scala.Option's value
if this scala.Option is nonempty.
the expression to evaluate and return if this is empty
toRight
Returns a singleton list containing the scala.Option's value if it is nonempty, or the empty list if the scala.Option is empty.
[use case] Converts this option to a map.
Converts this option 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.
a map of type immutable.Map[T, U]
containing all key/value pairs of type (T, U) of this option.
Returns a scala.util.Left containing the given
argument left if this scala.Option is empty, or
a scala.util.Right containing this scala.Option's value if
this is nonempty.
Returns a scala.util.Left containing the given
argument left if this scala.Option is empty, or
a scala.util.Right containing this scala.Option's value if
this is nonempty.
the expression to evaluate and return if this is empty
toLeft
Converts this iterable collection to a sequence.
Converts this iterable collection 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 iterable collection.
Converts this iterable collection to a set.
Converts this iterable collection to a set.
Note: will not terminate for infinite-sized collections.
a set containing all elements of this iterable collection.
Converts this iterable collection to a stream.
Converts this iterable collection to a stream.
Note: will not terminate for infinite-sized collections.
a stream containing all elements of this iterable collection.
Creates a String representation of this object.
Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.
a String representation of the object.
Converts this iterable collection to an unspecified Traversable.
Converts this iterable collection to an unspecified Traversable. Will return the same collection if this instance is already Traversable.
Note: will not terminate for infinite-sized collections.
a Traversable containing all elements of this iterable collection.
Converts this iterable collection to a Vector.
Converts this iterable collection to a Vector.
Note: will not terminate for infinite-sized collections.
a vector containing all elements of this iterable collection.
Transposes this iterable collection of traversable collections into a iterable collection of iterable collections.
Transposes this iterable collection of traversable collections into a iterable collection of iterable collections.
the type of the elements of each traversable collection.
an implicit conversion which asserts that the
element type of this iterable collection is a Traversable.
a two-dimensional iterable collection of iterable collections which has as nth row the nth column of this iterable collection.
(Changed in version 2.9.0) transpose throws an IllegalArgumentException if collections are not uniformly sized.
if all collections in this iterable collection are not of the same size.
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.
the type of the first half of the element pairs
the type of the second half of the element pairs
an implicit conversion which asserts that the element type of this iterable collection is a pair.
a pair iterable collections, containing the first, respectively second half of each element pair of this iterable collection.
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.
the type of the first member of the element triples
the type of the second member of the element triples
the type of the third member of the element triples
an implicit conversion which asserts that the element type of this iterable collection is a triple.
a triple iterable collections, containing the first, second, respectively third member of each element triple of this iterable collection.
Creates a non-strict view of a slice of this iterable collection.
Creates a non-strict view of a slice of this iterable collection.
Note: the difference between view and slice is that view produces
a view of the current iterable collection, whereas slice produces a new iterable collection.
Note: view(from, to) is equivalent to view.slice(from, to)
Note: might return different results for different runs, unless the underlying collection type is ordered.
the index of the first element of the view
the index of the element following the view
a non-strict view of a slice of this iterable collection, starting at index from
and extending up to (but not including) index until.
Creates a non-strict view of this iterable collection.
Creates a non-strict view of this iterable collection.
a non-strict view of this iterable collection.
Necessary to keep scala.Option from being implicitly converted to
scala.collection.Iterable in for comprehensions.
Necessary to keep scala.Option from being implicitly converted to
scala.collection.Iterable in for comprehensions.
[use case] Returns a option formed from this option and another iterable collection by combining corresponding elements in pairs.
Returns a option formed from this option and another iterable collection by combining corresponding elements in pairs. If one of the two collections is longer than the other, its remaining elements are ignored.
the type of the second half of the returned pairs
The iterable providing the second half of each result pair
a new option containing pairs consisting of
corresponding elements of this option and that. The length
of the returned collection is the minimum of the lengths of this option and that.
[use case] Returns a option formed from this option and another iterable collection by combining corresponding elements in pairs.
Returns a option formed from this option and another iterable collection by combining corresponding elements in pairs. If one of the two collections is shorter than the other, placeholder elements are used to extend the shorter collection to the length of the longer.
the type of the second half of the returned pairs
The iterable providing the second half of each result pair
the element to be used to fill up the result if this option is shorter than that.
the element to be used to fill up the result if that is shorter than this option.
a new option containing pairs consisting of
corresponding elements of this option and that. The length
of the returned collection is the maximum of the lengths of this option and that.
If this option is shorter than that, thisElem values are used to pad the result.
If that is shorter than this option, thatElem values are used to pad the result.
[use case] Zips this option with its indices.
Zips this option with its indices.
A new option containing pairs consisting of all elements of this
option paired with their index. Indices start at 0.
List("a", "b", "c").zipWithIndex = List(("a", 0), ("b", 1), ("c", 2))
Method called from equality methods, so that user-defined subclasses can refuse to be equal to other collections of the same kind.
Method called from equality methods, so that user-defined subclasses can refuse to be equal to other collections of the same kind.
The object with which this iterable collection should be compared
true, if this iterable collection can possibly equal that, false otherwise. The test
takes into consideration only the run-time types of objects but ignores their elements.
(option: Iterable[A]).canEqual(that)
[use case] Builds a new collection by applying a partial function to all elements of this option on which the function is defined.
Builds a new collection by applying a partial function to all elements of this option on which the function is defined.
the element type of the returned collection.
the partial function which filters and maps the option.
a new option 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.
(option: Iterable[A]).collect(pf)
Tests whether a predicate holds for some of the elements of this iterable collection.
Tests whether a predicate holds for some of the elements of this iterable collection.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
true if the given predicate p holds for some of the
elements of this iterable collection, otherwise false.
(option: Iterable[A]).exists(p)
Selects all elements of this iterable collection which satisfy a predicate.
Selects all elements of this iterable collection which satisfy a predicate.
the predicate used to test elements.
a new iterable collection consisting of all elements of this iterable collection that satisfy the given
predicate p. The order of the elements is preserved.
(option: Iterable[A]).filter(p)
Selects all elements of this iterable collection which do not satisfy a predicate.
Selects all elements of this iterable collection which do not satisfy a predicate.
the predicate used to test elements.
a new iterable collection consisting of all elements of this iterable collection that do not satisfy the given
predicate p. The order of the elements is preserved.
(option: Iterable[A]).filterNot(p)
[use case] Builds a new collection by applying a function to all elements of this option and using the elements of the resulting collections.
Builds a new collection by applying a function to all elements of this option 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 option. 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 a 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 option resulting from applying the given collection-valued function
f to each element of this option and concatenating the results.
(option: Iterable[A]).flatMap(f)
[use case] Converts this option of traversable collections into a option formed by the elements of these traversable collections.
Converts this option of traversable collections into a option formed by the elements of these traversable collections.
The resulting collection's type will be guided by the static type of option. For example:
val xs = List(Set(1, 2, 3), Set(1, 2, 3)) // xs == List(1, 2, 3, 1, 2, 3) val ys = Set(List(1, 2, 3), List(3, 2, 1)) // ys == Set(1, 2, 3)
the type of the elements of each traversable collection.
a new option resulting from concatenating all element options.
(option: Iterable[A]).flatten
Folds the elements of this iterable collection using the specified associative binary operator.
Folds the elements of this iterable collection using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
a type parameter for the binary operator, a supertype of A.
a neutral element for the fold operation; may be added to the result
an arbitrary number of times, and must not change the result (e.g., Nil for list concatenation,
0 for addition, or 1 for multiplication.)
a binary operator that must be associative
the result of applying fold operator op between all the elements and z
(option: Iterable[A]).fold(z)(op)
Tests whether a predicate holds for all elements of this iterable collection.
Tests whether a predicate holds for all elements of this iterable collection.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
true if the given predicate p holds for all elements
of this iterable collection, otherwise false.
(option: Iterable[A]).forall(p)
[use case] Applies a function f to all elements of this option.
Applies a function f to all elements of this option.
Note: this method underlies the implementation of most other bulk operations. Subclasses should re-implement this method if a more efficient implementation exists.
the function that is applied for its side-effect to every element.
The result of function f is discarded.
(option: Iterable[A]).foreach(f)
Tests whether this iterable collection is empty.
Tests whether this iterable collection is empty.
true if the iterable collection contain no elements, false otherwise.
(option: Iterable[A]).isEmpty
Creates a new iterator over all elements contained in this iterable object.
Creates a new iterator over all elements contained in this iterable object.
the new iterator
(option: Iterable[A]).iterator
[use case] Builds a new collection by applying a function to all elements of this option.
Builds a new collection by applying a function to all elements of this option.
the element type of the returned collection.
the function to apply to each element.
a new option resulting from applying the given function
f to each element of this option and collecting the results.
(option: Iterable[A]).map(f)
Tests whether the iterable collection is not empty.
Tests whether the iterable collection is not empty.
true if the iterable collection contains at least one element, false otherwise.
(option: Iterable[A]).nonEmpty
(option: StringAdd).self
(option: StringFormat).self
Converts this iterable collection to a list.
Converts this iterable collection to a list.
Note: will not terminate for infinite-sized collections.
a list containing all elements of this iterable collection.
(option: Iterable[A]).toList
Converts this iterable collection to a string.
Converts this iterable collection to a string.
a string representation of this collection. By default this
string consists of the stringPrefix of this iterable collection, followed
by all elements separated by commas and enclosed in parentheses.
(option: Iterable[A]).toString()
Creates a non-strict filter of this iterable collection.
Creates a non-strict filter of this iterable collection.
Note: the difference between c filter p and c withFilter p is that
the former creates a new collection, whereas the latter only
restricts the domain of subsequent map, flatMap, foreach,
and withFilter operations.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the predicate used to test elements.
an object of class WithFilter, which supports
map, flatMap, foreach, and withFilter operations.
All these operations apply to those elements of this iterable collection
which satisfy the predicate p.
(option: Iterable[A]).withFilter(p)
A syntactic sugar for out of order folding.
A syntactic sugar for out of order folding. See fold.
Example:
scala> val a = LinkedList(1,2,3,4) a: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4) scala> val b = (a /:\ 5)(_+_) b: Int = 15
(Since version 2.10.0) use fold instead
(option: ArrowAssoc[Option[A]]).x
(Since version 2.10.0) Use leftOfArrow instead
(option: Ensuring[Option[A]]).x
(Since version 2.10.0) Use resultOfEnsuring instead
Represents optional values. Instances of
Optionare either an instance of scala.Some or the objectNone.The most idiomatic way to use an scala.Option instance is to treat it as a collection or monad and use
map,flatMap,filter, orforeach:Note that this is equivalent to
Because of how for comprehension works, if
Noneis returned fromrequest.getParameter, the entire expression results inNoneThis allows for sophisticated chaining of scala.Option values without having to check for the existence of a value.
A less-idiomatic way to use scala.Option values is via pattern matching:
1.1, 16/01/2007
Many of the methods in here are duplicative with those in the Traversable hierarchy, but they are duplicated for a reason: the implicit conversion tends to leave one with an Iterable in situations where one could have retained an Option.