The first element returned by the iterator, if any, or null if this stream is empty. For a stream with an unstable iteration order, a different value might be produced each time first is evaluated.

The last element returned by the iterator, if any, or null if this stream is empty. In the case of an infinite stream, this operation never terminates; furthermore, this default implementation iterates all elements, which might be very expensive.

A stream containing all but the first element of this stream. For a stream with an unstable iteration order, a different stream might be produced each time rest is evaluated.

Therefore, if the stream i has an unstable iteration order, the stream { i.first, *i.rest } might not have the same elements as i.

The number of elements returned by the Iterable.iterator() of this stream, if the iterator terminates. In the case of an infinite stream, this operation never terminates.

Determines if there is at least one element of this stream that satisfies the given predicate function. If the stream is empty, returns false. For an infinite stream, this operation might not terminate.

A shallow copy of this collection, that is, a collection with identical elements which does not change if this collection changes. If this collection is immutable, it is acceptable to return a reference to this collection. If this collection is mutable, a newly instantiated collection must be returned.

Produce a new sequence containing the results of applying the given mapping to the elements of this stream.

This operation is an eager counterpart to Iterable.map(). For any stream it, and mapping f:

it.collect(f) == [*it.map(f)]

Returns true if the given value belongs to this Category, that is, if it is an element of this Category, or false otherwise.

For most Categorys the following relationship is satisfied by every pair of elements x and y:

• if x==y, then x in category == y in category

However, it is possible to form a useful Category consistent with some other equivalence relation, for example ===. Therefore implementations of contains() which do not satisfy this relationship are tolerated.

Produces the number of elements in this stream that satisfy the given predicate function. For an infinite stream, this method never terminates.

Call the given function for each element of this stream, passing the elements in the order they occur in this stream.

For example:

words.each((word) {
    print(word.lowercased);
    print(word.uppercased);
});

Has the same effect as the following for loop:

for (word in words) {
    print(word.lowercased);
    print(word.uppercased);
}

For certain streams this method is highly efficient, surpassing the performance of for loops on the JVM. Thus, each() is sometimes preferred in highly performance-critical low-level code.

Determines if all elements of this stream satisfy the given predicate function. If the stream is empty, return true. For an infinite stream, this operation might not terminate.

The first element of this stream which satisfies the given predicate function, if any, or null if there is no such element. For an infinite stream, this method might not terminate.

For example, the expression

(-10..10).find(Integer.positive)

evaluates to 1.

The last element of this stream which satisfies the given predicate function, if any, or null if there is no such element. For an infinite stream, this method will not terminate.

For example, the expression

(-10..10).findLast(3.divides)

evaluates to 9.

The indexth element returned by an iterator of this stream, or null if there are fewer than index+1 elements in the stream. For a stream with an unstable iteration order, a different value might be produced each time getFromFirst(index) is called for a given integer index.

An iterator for the elements belonging to this stream.

Obtain a measure containing the mapped values starting from the given starting index, with the given length. If length<=0, the resulting measure is empty.

The measure should contain the given number of elements of this stream, starting from the element at the given starting index, in the same order as they are produced by the Iterable.iterator() of the stream. In the case where the iterator would be exhausted before length elements are produced, the resulting measure contains only those elements which were produced before the iterator was exhausted, and the length of the measure is less then the given length.

When the given index does not belong to this ranged object, the behavior is implementation dependent.

Beginning with the Iterable.first element of this stream, apply the given combining function to each element of this stream in turn, progressively accumulating a single result.

For an empty stream, reduce() always returns null.

For a stream with one element, reduce() returns that element:

{ first }.reduce(f) == first

For a given stream it with more than one element, and combining function f, the result of reduce() is obtained according to the following recursive definition:

it.reduce(f) == f(it.exceptLast.reduce(f), it.last)

For example, the expression

(1..100).reduce(plus)

results in the integer 5050.

Produce a new sequence containing the elements of this stream, sorted according to the given comparator function imposing a partial order upon the elements of the stream.

For convenience, the functions byIncreasing() and byDecreasing() produce suitable comparator functions.

For example, this expression

"Hello World!".sort(byIncreasing(Character.lowercased))

evaluates to the sequence [ , !, d, e, H, l, l, l, o, o, r, W].

This operation is eager by nature.

Note that the toplevel function sort() may be used to sort a stream of Comparable values according to the natural order of its elements.

Obtain a span containing the elements between the two given indices.

The span should contain elements of this stream, starting from the element at the given starting index, and ending with the element at the given ending index, in the same order as they are produced by the Iterable.iterator() of the stream, except when the ending index occurs earlier than the starting index, in which case they occur in the opposite order.

When one or both of the given indices does not belong to this ranged stream, the behavior is implementation dependent.

Obtain a span containing the elements between the given starting index and the last index of this ranged object.

The span should contain elements of this stream, starting from the element at the given starting index, in the same order as they are produced by the Iterable.iterator() of the stream.

When the given index does not belong to this ranged stream, the behavior is implementation dependent.

Obtain a span containing the elements between the first index of this ranged stream and given end index.

The span should contain elements of this stream, up to the element at the given ending index, in the same order as they are produced by the Iterable.iterator() of the stream.

When the given index does not belong to this ranged stream, the behavior is implementation dependent.