Iterator Sequencing

for Stage 2

Michael Ficarra • June 2024

reminder: goals

• conveniently compose 2 iterators
• conveniently compose 0 or more iterators
• compose an infinite sequence of iterators
• conveniently interleave other values among the iterators
• discoverable, familiar pattern

solution space considered

• variadic Iterator.from(...iterators)
• Iterator.prototype.flat()
• Iterator.prototype.append(...iterators)
• Iterator.concat(iteratorOfIterators)
• Iterator.concat(...iterators)

previous strategy

• variadic Iterator.from
• for when you have a small number of iterators/iterables
• Iterator.prototype.flat
• for when you have an iterator/iterable of iterators/iterables

feedback:

• because of an optimisation in Iterator.from, the 1-arg case is observably slightly different than 0 or 2+ args
• questions about optimisability of Iterator.prototype.flat
• unclear whether infinite iterators of iterators are common enough to motivate flat
• unclear who is responsible for closing iterators produced by the target of flat, or how that would work when infinitely many may be produced

new goals

• conveniently compose 2 iterators
• conveniently compose 0 or more iterators
• compose an infinite sequence of iterators
• conveniently interleave other values among the iterators
• discoverable, familiar pattern
• no observable difference between 1-iterator case and 0+ iterators

Iterator.concat(...iterators)

• ✓ conveniently compose 2 iterators
• ✓ conveniently compose 0 or more iterators
• ✓ conveniently interleave other values among the iterators (using [] wrapper)
• ✓ discoverable, intuitive pattern
• ✓ no observable difference between 1-iterator case and 0+ iterators

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• ✘ JHD doesn't like the name "concat" for this

name alternatives (in champion preference order)

• concat
• concatenate
• sequence
• join
• combine
• fuse
• cat
• chain

full spec text

polyfill & basic tests

Stage 2?

assign reviewers?