as_iterator.flexseq: Iterate over a 'flexseq' (coro iterator)

In Immutables: Fast and Functional Data Structures

Iterate over a flexseq (coro iterator)

Description

Returns a lazy iterator that yields payload elements left-to-right. Use with loop() as the canonical iteration form:

Usage

## S3 method for class 'flexseq'
as_iterator(x)

Arguments

x	A flexseq.

Details

loop(for (x in s) print(x))

Iteration uses repeated left-view (viewL) and is O(n) total, O(1) amortized per step. The original x is not modified; the iterator holds a private cursor over progressively-smaller tails.

For named sequences, internal name metadata is stripped from yielded values to match peek_front(s) semantics. Access names via as.list() when needed.

Inherited by ordered_sequence and interval_index: for those subclasses the yielded value is the unwrapped payload (keys / interval endpoints dropped), in key-ascending / start-position order respectively. See as_iterator.priority_queue() for the priority-order override.

Value

A coro iterator function.

Do not use plain for directly

Writing for (x in s) ... (without loop()) will not dispatch this method. R's for walks the object's underlying list storage at the C level and bypasses S3 length/[[, so it silently yields raw finger-tree internals (Digit/Empty/Deep nodes) rather than sequence elements. Always wrap with loop(), or call as.list() first for an eager copy.

Examples

s <- flexseq("a", "b", "c")
loop(for (x in s) print(x))

Immutables documentation built on April 29, 2026, 1:06 a.m.