Package-level declarations
Sequence type that represents lazily evaluated collections. Top-level functions for instantiating sequences and extension functions for sequences.
Classification of sequences
The sequence operations can be classified into the following groups regarding their state requirements:
stateless – operations which require no state and process each element independently like kotlin.sequences.Sequence.map, kotlin.sequences.Sequence.filter, or require a small constant amount of state to process an element, for example kotlin.sequences.Sequence.take or kotlin.sequences.Sequence.drop;
stateful – operations which require a significant amount of state, usually proportional to the number of elements in a sequence.
If the sequence operation returns another sequence, which is produced lazily, it's called intermediate, and otherwise the operation is terminal. Examples of terminal operations are kotlin.sequences.Sequence.toList, kotlin.sequences.Sequence.max.
Sequences can be iterated multiple times, however some sequence implementations might constrain themselves to be iterated only once. That is mentioned specifically in their documentation (e.g. kotlin.sequences.generateSequence overload). The latter sequences throw an exception on an attempt to iterate them the second time.
Functions
Creates a sequence that returns all values from this enumeration. The sequence is constrained to be iterated only once.
Creates a sequence that returns all elements from this iterator. The sequence is constrained to be iterated only once.
Returns this sequence as a Sequence.
Returns a Map containing the elements from the given sequence indexed by the key returned from keySelector function applied to each element.
Returns a Map containing the values provided by valueTransform and indexed by keySelector functions applied to elements of the given sequence.
Populates and returns the destination mutable map with key-value pairs, where key is provided by the keySelector function applied to each element of the given sequence and value is the element itself.
Populates and returns the destination mutable map with key-value pairs, where key is provided by the keySelector function and and value is provided by the valueTransform function applied to elements of the given sequence.
Returns an average value of elements in the sequence.
Appends all elements matching the given predicate to the given destination.
Returns a sequence containing all elements that are instances of specified type parameter R.
Returns a sequence containing all elements that are instances of specified class.
Appends all elements that are instances of specified type parameter R to the given destination.
Appends all elements that are instances of specified class to the given destination.
Appends all elements that are not null
to the given destination.
Appends all elements not matching the given predicate to the given destination.
Returns a sequence of all elements from all iterables in this sequence.
Returns a sequence of all elements from all sequences in this sequence.
Returns a sequence which invokes the function to calculate the next value on each iteration until the function returns null
.
Returns a sequence defined by the starting value seed and the function nextFunction, which is invoked to calculate the next value based on the previous one on each iteration.
Returns a sequence defined by the function seedFunction, which is invoked to produce the starting value, and the nextFunction, which is invoked to calculate the next value based on the previous one on each iteration.
Groups elements of the original sequence by the key returned by the given keySelector function applied to each element and returns a map where each group key is associated with a list of corresponding elements.
Groups values returned by the valueTransform function applied to each element of the original sequence by the key returned by the given keySelector function applied to the element and returns a map where each group key is associated with a list of corresponding values.
Groups elements of the original sequence by the key returned by the given keySelector function applied to each element and puts to the destination map each group key associated with a list of corresponding elements.
Groups values returned by the valueTransform function applied to each element of the original sequence by the key returned by the given keySelector function applied to the element and puts to the destination map each group key associated with a list of corresponding values.
Appends the string from all the elements separated using separator and using the given prefix and postfix if supplied.
Creates a string from all the elements separated using separator and using the given prefix and postfix if supplied.
Applies the given transform function to each element and its index in the original sequence and appends only the non-null results to the given destination.
Applies the given transform function to each element and its index in the original sequence and appends the results to the given destination.
Applies the given transform function to each element in the original sequence and appends only the non-null results to the given destination.
Returns a sequence containing all elements of the original sequence without the first occurrence of the given element.
Returns a sequence containing all elements of original sequence except the elements contained in the given elements array.
Returns a sequence containing all elements of original sequence except the elements contained in the given elements collection.
Returns a sequence containing all elements of original sequence except the elements contained in the given elements sequence.
Returns a sequence containing all elements of the original sequence and then the given element.
Returns a sequence containing all elements of original sequence and then all elements of the given elements array.
Returns a sequence containing all elements of original sequence and then all elements of the given elements collection.
Returns a sequence containing all elements of original sequence and then all elements of the given elements sequence.
Returns an original collection containing all the non-null
elements, throwing an IllegalArgumentException if there are any null
elements.
Creates a sequence that returns the specified values.
Returns the single element, or throws an exception if the sequence is empty or has more than one element.
Returns the single element matching the given predicate, or throws exception if there is no or more than one matching element.
Returns single element, or null
if the sequence is empty or has more than one element.
Returns the single element matching the given predicate, or null
if element was not found or more than one element was found.
Returns a sequence that yields elements of this sequence sorted descending according to their natural sort order.
Returns a sequence that yields elements of this sequence sorted according to the specified comparator.
Returns the sum of all elements in the sequence.
Appends all elements to the given destination collection.
Returns a new MutableList filled with all elements of this sequence.
Returns a new MutableSet containing all distinct elements from the given sequence.
Returns a new SortedSet of all elements.
Returns a sequence that wraps each element of the original sequence into an IndexedValue containing the index of that element and the element itself.
Returns a sequence of values built from the elements of this
sequence and the other sequence with the same index. The resulting sequence ends as soon as the shortest input sequence ends.
Returns a sequence of values built from the elements of this
sequence and the other sequence with the same index using the provided transform function applied to each pair of elements. The resulting sequence ends as soon as the shortest input sequence ends.