Uses of Interface
io.vavr.collection.Traversable

Packages that use Traversable

Package	Description
io.vavr	Beside API the io.vavr package contains core types like (Checked)Functions and Tuples.
io.vavr.collection	Purely functional collections based on Traversable.

Uses of Traversable in io.vavr

Methods in io.vavr with type parameters of type Traversable

Modifier and Type	Method	Description
static <T,R extends Traversable<T>> R	ValueModule.toTraversable(Value<T> value, R empty, java.util.function.Function<T,R> ofElement, java.util.function.Function<java.lang.Iterable<T>,R> ofAll)

Uses of Traversable in io.vavr.collection

Classes in io.vavr.collection with type parameters of type Traversable

Modifier and Type	Class	Description
private static class	JavaConverters.HasDelegate<C extends Traversable<?>>	Encapsulates the access to delegate and performs mutability checks.

Subinterfaces of Traversable in io.vavr.collection

Modifier and Type	Interface	Description
interface	BitSet<T>	An immutable BitSet implementation.
interface	IndexedSeq<T>	Interface for immutable, indexed sequences.
interface	Iterator<T>	io.vavr.collection.Iterator is a compositional replacement for java.util.Iterator whose purpose is to iterate once over a sequence of elements.
interface	LinearSeq<T>	Interface for immutable, linear sequences.
interface	List<T>	An immutable List is an eager sequence of elements.
interface	Map<K,V>	An immutable Map interface.
interface	Multimap<K,V>	An immutable Multimap interface.
interface	Seq<T>	Interface for immutable sequential data structures.
interface	Set<T>	An immutable Set interface.
interface	SortedMap<K,V>	An immutable SortedMap interface.
interface	SortedMultimap<K,V>	An immutable SortedMultimap interface.
interface	SortedSet<T>	An immutable SortedSet interface.
interface	Stream<T>	An immutable Stream is lazy sequence of elements which may be infinitely long.
interface	Tree<T>	A general Tree interface.

Classes in io.vavr.collection that implement Traversable

Modifier and Type	Class	Description
(package private) class	AbstractIterator<T>	Provides a common Object.toString() implementation.
(package private) class	AbstractMultimap<K,V,M extends Multimap<K,V>>	An Multimap implementation (not intended to be public).
(package private) class	AbstractQueue<T,Q extends AbstractQueue<T,Q>>
class	Array<T>	Array is a Traversable wrapper for Object[] containing elements of type T.
static class	BitSetModule.AbstractBitSet<T>
static class	BitSetModule.BitSet1<T>
static class	BitSetModule.BitSet2<T>
static class	BitSetModule.BitSetIterator<T>
static class	BitSetModule.BitSetN<T>
class	CharSeq	The CharSeq (read: character sequence) collection essentially is a rich String wrapper having all operations we know from the functional Vavr collections.
static class	HashArrayMappedTrieModule.LeafNodeIterator<K,V>
class	HashMap<K,V>	An immutable HashMap implementation based on a Hash array mapped trie (HAMT).
class	HashMultimap<K,V>	A HashMap-based implementation of Multimap
class	HashSet<T>	An immutable HashSet implementation.
static class	IteratorModule.CachedIterator<T>
static class	IteratorModule.ConcatIterator<T>
static class	IteratorModule.DistinctIterator<T,U>
static class	IteratorModule.EmptyIterator
static class	IteratorModule.GroupedIterator<T>
class	LinkedHashMap<K,V>	An immutable LinkedHashMap implementation that has predictable (insertion-order) iteration.
class	LinkedHashMultimap<K,V>	A LinkedHashMap-based implementation of Multimap
class	LinkedHashSet<T>	An immutable HashSet implementation that has predictable (insertion-order) iteration.
static class	List.Cons<T>	Non-empty List, consisting of a head and a tail.
static class	List.Nil<T>	Representation of the singleton empty List.
class	PriorityQueue<T>	A PriorityQueue.
class	Queue<T>	An immutable Queue stores elements allowing a first-in-first-out (FIFO) retrieval.
static class	Stream.Cons<T>	Non-empty Stream, consisting of a head, and tail.
static class	Stream.Empty<T>	The empty Stream.
static class	StreamModule.AppendElements<T>
static class	StreamModule.ConsImpl<T>
static class	StreamModule.FlatMapIterator<T,U>
static class	StreamModule.StreamIterator<T>
static class	Tree.Empty<T>	The empty tree.
static class	Tree.Node<T>	Represents a tree node.
class	TreeMap<K,V>	SortedMap implementation, backed by a Red/Black Tree.
class	TreeMultimap<K,V>	A TreeMap-based implementation of Multimap
class	TreeSet<T>	SortedSet implementation, backed by a Red/Black Tree.
class	Vector<T>	Vector is the default Seq implementation that provides effectively constant time access to any element.

Fields in io.vavr.collection declared as Traversable

Modifier and Type	Field	Description
private C	JavaConverters.HasDelegate.delegate

Fields in io.vavr.collection with type parameters of type Traversable

Modifier and Type	Field	Description
private java.util.function.BiFunction<Traversable<?>,java.lang.Object,Traversable<?>>	Multimap.ContainerType.add
private java.util.function.BiFunction<Traversable<?>,java.lang.Object,Traversable<?>>	Multimap.ContainerType.add
protected Map<K,Traversable<V>>	AbstractMultimap.back
protected AbstractMultimap.SerializableSupplier<Traversable<?>>	AbstractMultimap.emptyContainer
private AbstractMultimap.SerializableSupplier<Traversable<?>>	HashMultimap.Builder.emptyContainer
private AbstractMultimap.SerializableSupplier<Traversable<?>>	LinkedHashMultimap.Builder.emptyContainer
private AbstractMultimap.SerializableSupplier<Traversable<?>>	TreeMultimap.Builder.emptyContainer
private java.util.function.BiFunction<Traversable<?>,java.lang.Object,Traversable<?>>	Multimap.ContainerType.remove
private java.util.function.BiFunction<Traversable<?>,java.lang.Object,Traversable<?>>	Multimap.ContainerType.remove

Methods in io.vavr.collection with type parameters of type Traversable

Modifier and Type	Method	Description
(package private) static <C extends Traversable<T>,T> C	Collections.fill(int n, java.util.function.Supplier<? extends T> s, C empty, java.util.function.Function<T[],C> of)
(package private) static <C extends Traversable<T>,T> C	Collections.fillObject(int n, T element, C empty, java.util.function.Function<T[],C> of)
(package private) static <C extends Traversable<T>,T> Tuple2<C,C>	Collections.partition(C collection, java.util.function.Function<java.lang.Iterable<T>,C> creator, java.util.function.Predicate<? super T> predicate)
(package private) static <C extends Traversable<T>,T> C	Collections.reject(C source, java.util.function.Predicate<? super T> predicate)
(package private) static <C extends Traversable<T>,T> C	Collections.removeAll(C source, java.lang.Iterable<? extends T> elements)
(package private) static <C extends Traversable<T>,T> C	Collections.removeAll(C source, T element)
(package private) static <C extends Traversable<T>,T> C	Collections.retainAll(C source, java.lang.Iterable<? extends T> elements)
(package private) static <T,U,R extends Traversable<U>> R	Collections.scanLeft(Traversable<? extends T> source, U zero, java.util.function.BiFunction<? super U,? super T,? extends U> operation, java.util.function.Function<Iterator<U>,R> finisher)
(package private) static <T,U,R extends Traversable<U>> R	Collections.scanRight(Traversable<? extends T> source, U zero, java.util.function.BiFunction<? super T,? super U,? extends U> operation, java.util.function.Function<Iterator<U>,R> finisher)
(package private) static <C extends Traversable<T>,T> C	Collections.tabulate(int n, java.util.function.Function<? super java.lang.Integer,? extends T> f, C empty, java.util.function.Function<T[],C> of)

Methods in io.vavr.collection that return Traversable

Modifier and Type	Method	Description
(package private) <T> Traversable<T>	Multimap.ContainerType.add(Traversable<?> container, T elem)
default Traversable<V>	Multimap.apply(K key)	Deprecated.
<R> Traversable<R>	Traversable.collect(PartialFunction<? super T,? extends R> partialFunction)	Collects all elements that are in the domain of the given partialFunction by mapping the elements to type R.
Traversable<T>	Traversable.distinct()	Returns a new version of this which contains no duplicates.
Traversable<T>	Traversable.distinctBy(java.util.Comparator<? super T> comparator)	Returns a new version of this which contains no duplicates.
<U> Traversable<T>	Traversable.distinctBy(java.util.function.Function<? super T,? extends U> keyExtractor)	Returns a new version of this which contains no duplicates.
Traversable<T>	Traversable.drop(int n)	Drops the first n elements of this or all elements, if this length < n.
Traversable<T>	Traversable.dropRight(int n)	Drops the last n elements of this or all elements, if this length < n.
Traversable<T>	Traversable.dropUntil(java.util.function.Predicate<? super T> predicate)	Drops elements until the predicate holds for the current element.
Traversable<T>	Traversable.dropWhile(java.util.function.Predicate<? super T> predicate)	Drops elements while the predicate holds for the current element.
Traversable<T>	Traversable.filter(java.util.function.Predicate<? super T> predicate)	Returns a new traversable consisting of all elements which satisfy the given predicate.
<U> Traversable<U>	Traversable.flatMap(java.util.function.Function<? super T,? extends java.lang.Iterable<? extends U>> mapper)	FlatMaps this Traversable.
Traversable<V>	AbstractMultimap.getOrElse(K key, Traversable<? extends V> defaultValue)
Traversable<V>	Multimap.getOrElse(K key, Traversable<? extends V> defaultValue)	Returns the value associated with a key, or a default value if the key is not contained in the map
Traversable<T>	Traversable.init()	Dual of tail(), returning all elements except the last.
<U> Traversable<U>	Traversable.map(java.util.function.Function<? super T,? extends U> mapper)	Maps the elements of this Traversable to elements of a new type preserving their order, if any.
static <T> Traversable<T>	Traversable.narrow(Traversable<? extends T> traversable)	Narrows a widened Traversable<? extends T> to Traversable<T> by performing a type-safe cast.
Traversable<T>	Traversable.orElse(java.lang.Iterable<? extends T> other)	Returns this Traversable if it is nonempty, otherwise return the alternative.
Traversable<T>	Traversable.orElse(java.util.function.Supplier<? extends java.lang.Iterable<? extends T>> supplier)	Returns this Traversable if it is nonempty, otherwise return the result of evaluating supplier.
Traversable<T>	Traversable.peek(java.util.function.Consumer<? super T> action)
default Traversable<T>	Traversable.reject(java.util.function.Predicate<? super T> predicate)	Returns a new traversable consisting of all elements which do not satisfy the given predicate.
(package private) <T> Traversable<T>	Multimap.ContainerType.remove(Traversable<?> container, T elem)
Traversable<T>	Traversable.replace(T currentElement, T newElement)	Replaces the first occurrence (if exists) of the given currentElement with newElement.
Traversable<T>	Traversable.replaceAll(T currentElement, T newElement)	Replaces all occurrences of the given currentElement with newElement.
Traversable<T>	Traversable.retainAll(java.lang.Iterable<? extends T> elements)	Keeps all occurrences of the given elements from this.
default Traversable<T>	Iterator.scan(T zero, java.util.function.BiFunction<? super T,? super T,? extends T> operation)
Traversable<T>	Traversable.scan(T zero, java.util.function.BiFunction<? super T,? super T,? extends T> operation)	Computes a prefix scan of the elements of the collection.
<U> Traversable<U>	Traversable.scanLeft(U zero, java.util.function.BiFunction<? super U,? super T,? extends U> operation)	Produces a collection containing cumulative results of applying the operator going left to right.
<U> Traversable<U>	Traversable.scanRight(U zero, java.util.function.BiFunction<? super T,? super U,? extends U> operation)	Produces a collection containing cumulative results of applying the operator going right to left.
Traversable<T>	Traversable.tail()	Drops the first element of a non-empty Traversable.
Traversable<T>	Traversable.take(int n)	Takes the first n elements of this or all elements, if this length < n.
Traversable<T>	Traversable.takeRight(int n)	Takes the last n elements of this or all elements, if this length < n.
Traversable<T>	Traversable.takeUntil(java.util.function.Predicate<? super T> predicate)	Takes elements until the predicate holds for the current element.
Traversable<T>	Traversable.takeWhile(java.util.function.Predicate<? super T> predicate)	Takes elements while the predicate holds for the current element.
Traversable<V>	AbstractMultimap.values()
Traversable<V>	Multimap.values()
<U> Traversable<Tuple2<T,U>>	Traversable.zip(java.lang.Iterable<? extends U> that)	Returns a traversable formed from this traversable and another Iterable collection by combining corresponding elements in pairs.
<U> Traversable<Tuple2<T,U>>	Traversable.zipAll(java.lang.Iterable<? extends U> that, T thisElem, U thatElem)	Returns a traversable formed from this traversable and another Iterable by combining corresponding elements in pairs.
<U,R> Traversable<R>	Traversable.zipWith(java.lang.Iterable<? extends U> that, java.util.function.BiFunction<? super T,? super U,? extends R> mapper)	Returns a traversable formed from this traversable and another Iterable collection by mapping elements.
Traversable<Tuple2<T,java.lang.Integer>>	Traversable.zipWithIndex()	Zips this traversable with its indices.
<U> Traversable<U>	Traversable.zipWithIndex(java.util.function.BiFunction<? super T,? super java.lang.Integer,? extends U> mapper)	Zips this traversable with its indices by applying mapper provided.

Methods in io.vavr.collection that return types with arguments of type Traversable

Modifier and Type	Method	Description
Map<K,Traversable<V>>	AbstractMultimap.asMap()
Map<K,Traversable<V>>	Multimap.asMap()	Converts this Multimap to a Map
default PartialFunction<K,Traversable<V>>	Multimap.asPartialFunction()	Turns this Multimap into a PartialFunction which is defined at a specific index, if this Multimap contains the given key.
Option<Traversable<V>>	AbstractMultimap.get(K key)
Option<Traversable<V>>	Multimap.get(K key)	Returns the Some of value to which the specified key is mapped, or None if this multimap contains no mapping for the key.
<C> Map<C,? extends Traversable<T>>	Traversable.groupBy(java.util.function.Function<? super T,? extends C> classifier)	Groups this elements by classifying the elements.
Iterator<? extends Traversable<T>>	Traversable.grouped(int size)	Groups this Traversable into fixed size blocks.
default Option<? extends Traversable<T>>	Traversable.initOption()	Dual of tailOption(), returning all elements except the last as Option.
Tuple2<? extends Traversable<T>,? extends Traversable<T>>	Traversable.partition(java.util.function.Predicate<? super T> predicate)	Creates a partition of this Traversable by splitting this elements in two in distinct traversables according to a predicate.
Tuple2<? extends Traversable<T>,? extends Traversable<T>>	Traversable.partition(java.util.function.Predicate<? super T> predicate)	Creates a partition of this Traversable by splitting this elements in two in distinct traversables according to a predicate.
Iterator<? extends Traversable<T>>	Traversable.slideBy(java.util.function.Function<? super T,?> classifier)	Slides a non-overlapping window of a variable size over this Traversable.
Iterator<? extends Traversable<T>>	Traversable.sliding(int size)	Slides a window of a specific size and step size 1 over this Traversable by calling sliding(int, int).
Iterator<? extends Traversable<T>>	Traversable.sliding(int size, int step)	Slides a window of a specific size and step size over this Traversable.
Tuple2<? extends Traversable<T>,? extends Traversable<T>>	Traversable.span(java.util.function.Predicate<? super T> predicate)	Returns a tuple where the first element is the longest prefix of elements that satisfy the given predicate and the second element is the remainder.
Tuple2<? extends Traversable<T>,? extends Traversable<T>>	Traversable.span(java.util.function.Predicate<? super T> predicate)	Returns a tuple where the first element is the longest prefix of elements that satisfy the given predicate and the second element is the remainder.
Option<? extends Traversable<T>>	Traversable.tailOption()	Drops the first element of a non-empty Traversable and returns an Option.
<T1,T2> Tuple2<? extends Traversable<T1>,? extends Traversable<T2>>	Traversable.unzip(java.util.function.Function<? super T,Tuple2<? extends T1,? extends T2>> unzipper)	Unzips this elements by mapping this elements to pairs which are subsequently split into two distinct sets.
<T1,T2> Tuple2<? extends Traversable<T1>,? extends Traversable<T2>>	Traversable.unzip(java.util.function.Function<? super T,Tuple2<? extends T1,? extends T2>> unzipper)	Unzips this elements by mapping this elements to pairs which are subsequently split into two distinct sets.
<T1,T2,T3> Tuple3<? extends Traversable<T1>,? extends Traversable<T2>,? extends Traversable<T3>>	Traversable.unzip3(java.util.function.Function<? super T,Tuple3<? extends T1,? extends T2,? extends T3>> unzipper)	Unzips this elements by mapping this elements to triples which are subsequently split into three distinct sets.
<T1,T2,T3> Tuple3<? extends Traversable<T1>,? extends Traversable<T2>,? extends Traversable<T3>>	Traversable.unzip3(java.util.function.Function<? super T,Tuple3<? extends T1,? extends T2,? extends T3>> unzipper)	Unzips this elements by mapping this elements to triples which are subsequently split into three distinct sets.
<T1,T2,T3> Tuple3<? extends Traversable<T1>,? extends Traversable<T2>,? extends Traversable<T3>>	Traversable.unzip3(java.util.function.Function<? super T,Tuple3<? extends T1,? extends T2,? extends T3>> unzipper)	Unzips this elements by mapping this elements to triples which are subsequently split into three distinct sets.

Methods in io.vavr.collection with parameters of type Traversable

Modifier and Type	Method	Description
(package private) <T> Traversable<T>	Multimap.ContainerType.add(Traversable<?> container, T elem)
Traversable<V>	AbstractMultimap.getOrElse(K key, Traversable<? extends V> defaultValue)
Traversable<V>	Multimap.getOrElse(K key, Traversable<? extends V> defaultValue)	Returns the value associated with a key, or a default value if the key is not contained in the map
private static <T,C> java.util.Set<java.util.Map.Entry<C,java.util.Collection<T>>>	Collections.groupBy(Traversable<T> source, java.util.function.Function<? super T,? extends C> classifier)
(package private) static <T,C,R extends java.lang.Iterable<T>> Map<C,R>	Collections.groupBy(Traversable<T> source, java.util.function.Function<? super T,? extends C> classifier, java.util.function.Function<? super java.lang.Iterable<T>,R> mapper)
(package private) static <T> T	Collections.last(Traversable<T> source)
static <T> Traversable<T>	Traversable.narrow(Traversable<? extends T> traversable)	Narrows a widened Traversable<? extends T> to Traversable<T> by performing a type-safe cast.
(package private) <T> Traversable<T>	Multimap.ContainerType.remove(Traversable<?> container, T elem)
(package private) static <T,U,R extends Traversable<U>> R	Collections.scanLeft(Traversable<? extends T> source, U zero, java.util.function.BiFunction<? super U,? super T,? extends U> operation, java.util.function.Function<Iterator<U>,R> finisher)
(package private) static <T,U,R extends Traversable<U>> R	Collections.scanRight(Traversable<? extends T> source, U zero, java.util.function.BiFunction<? super T,? super U,? extends U> operation, java.util.function.Function<Iterator<U>,R> finisher)

Method parameters in io.vavr.collection with type arguments of type Traversable

Modifier and Type	Method	Description
protected abstract <K2,V2> Multimap<K2,V2>	AbstractMultimap.createFromMap(Map<K2,Traversable<V2>> back)
protected <K2,V2> HashMultimap<K2,V2>	HashMultimap.createFromMap(Map<K2,Traversable<V2>> back)
protected <K2,V2> LinkedHashMultimap<K2,V2>	LinkedHashMultimap.createFromMap(Map<K2,Traversable<V2>> back)
protected <K2,V2> TreeMultimap<K2,V2>	TreeMultimap.createFromMap(Map<K2,Traversable<V2>> back)
<K2 extends K,V2 extends V> M	AbstractMultimap.merge(Multimap<K2,V2> that, java.util.function.BiFunction<Traversable<V>,Traversable<V2>,Traversable<V>> collisionResolution)
<K2 extends K,V2 extends V> M	AbstractMultimap.merge(Multimap<K2,V2> that, java.util.function.BiFunction<Traversable<V>,Traversable<V2>,Traversable<V>> collisionResolution)
<K2 extends K,V2 extends V> M	AbstractMultimap.merge(Multimap<K2,V2> that, java.util.function.BiFunction<Traversable<V>,Traversable<V2>,Traversable<V>> collisionResolution)
<K2 extends K,V2 extends V> Multimap<K,V>	Multimap.merge(Multimap<K2,V2> that, java.util.function.BiFunction<Traversable<V>,Traversable<V2>,Traversable<V>> collisionResolution)	Creates a new multimap which by merging the entries of this multimap and that multimap.
<K2 extends K,V2 extends V> Multimap<K,V>	Multimap.merge(Multimap<K2,V2> that, java.util.function.BiFunction<Traversable<V>,Traversable<V2>,Traversable<V>> collisionResolution)	Creates a new multimap which by merging the entries of this multimap and that multimap.
<K2 extends K,V2 extends V> Multimap<K,V>	Multimap.merge(Multimap<K2,V2> that, java.util.function.BiFunction<Traversable<V>,Traversable<V2>,Traversable<V>> collisionResolution)	Creates a new multimap which by merging the entries of this multimap and that multimap.
<K2 extends K,V2 extends V> SortedMultimap<K,V>	SortedMultimap.merge(Multimap<K2,V2> that, java.util.function.BiFunction<Traversable<V>,Traversable<V2>,Traversable<V>> collisionResolution)
<K2 extends K,V2 extends V> SortedMultimap<K,V>	SortedMultimap.merge(Multimap<K2,V2> that, java.util.function.BiFunction<Traversable<V>,Traversable<V2>,Traversable<V>> collisionResolution)
<K2 extends K,V2 extends V> SortedMultimap<K,V>	SortedMultimap.merge(Multimap<K2,V2> that, java.util.function.BiFunction<Traversable<V>,Traversable<V2>,Traversable<V>> collisionResolution)
(package private) static <K,V,M extends Map<K,V>> M	Maps.scan(M map, Tuple2<K,V> zero, java.util.function.BiFunction<? super Tuple2<K,V>,? super Tuple2<K,V>,? extends Tuple2<K,V>> operation, java.util.function.Function<Iterator<Tuple2<K,V>>,Traversable<Tuple2<K,V>>> finisher)

Constructor parameters in io.vavr.collection with type arguments of type Traversable

Constructor	Description
AbstractMultimap(Map<K,Traversable<V>> back, Multimap.ContainerType containerType, AbstractMultimap.SerializableSupplier<Traversable<?>> emptyContainer)
AbstractMultimap(Map<K,Traversable<V>> back, Multimap.ContainerType containerType, AbstractMultimap.SerializableSupplier<Traversable<?>> emptyContainer)
Builder(Multimap.ContainerType containerType, AbstractMultimap.SerializableSupplier<Traversable<?>> emptyContainer)
Builder(Multimap.ContainerType containerType, AbstractMultimap.SerializableSupplier<Traversable<?>> emptyContainer)
Builder(Multimap.ContainerType containerType, AbstractMultimap.SerializableSupplier<Traversable<?>> emptyContainer)
ContainerType(java.util.function.BiFunction<Traversable<?>,java.lang.Object,Traversable<?>> add, java.util.function.BiFunction<Traversable<?>,java.lang.Object,Traversable<?>> remove, java.util.function.Supplier<java.util.Collection<?>> instantiate)
ContainerType(java.util.function.BiFunction<Traversable<?>,java.lang.Object,Traversable<?>> add, java.util.function.BiFunction<Traversable<?>,java.lang.Object,Traversable<?>> remove, java.util.function.Supplier<java.util.Collection<?>> instantiate)
HashMultimap(Map<K,Traversable<V>> back, Multimap.ContainerType containerType, AbstractMultimap.SerializableSupplier<Traversable<?>> emptyContainer)
HashMultimap(Map<K,Traversable<V>> back, Multimap.ContainerType containerType, AbstractMultimap.SerializableSupplier<Traversable<?>> emptyContainer)
LinkedHashMultimap(Map<K,Traversable<V>> back, Multimap.ContainerType containerType, AbstractMultimap.SerializableSupplier<Traversable<?>> emptyContainer)
LinkedHashMultimap(Map<K,Traversable<V>> back, Multimap.ContainerType containerType, AbstractMultimap.SerializableSupplier<Traversable<?>> emptyContainer)
TreeMultimap(Map<K,Traversable<V>> back, Multimap.ContainerType containerType, AbstractMultimap.SerializableSupplier<Traversable<?>> emptyContainer)
TreeMultimap(Map<K,Traversable<V>> back, Multimap.ContainerType containerType, AbstractMultimap.SerializableSupplier<Traversable<?>> emptyContainer)