I would like to know what it means to flatten e.g. flatten an iterator of iterators. Can you tell me? Are there any C/Java/Python idioms for it?
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I would like to know what it means to flatten e.g. flatten an iterator of iterators. Can you tell me? Are there any C/Java/Python idioms for it?
In this context, to flatten means to remove nesting. For instance, an array of arrays (an array where each element is an array) of integers is nested; if we flatten it we get an array of integers which contains the same values in the same order, but next to each other in a single array, rather than split into several arrays:
[[1 2] [3 4]] -> [1 2 3 4]. Same difference with iterators, other collections, and deeper nesting (array of array of sets of iterators of strings).As for idioms, there aren’t really many — it’s not a common task, and often simple. Note that in the case of regular arrays (all nested arrays are of the same size),
nested[i][j]is equivalent tonested[i * INNER_ARRAY_SIZE + j]. This is sometimes used to avoid nesting, especially in languages which treat arrays as reference types and thus require many separately-allocated arrays if you nest them. In Python, you can flatten iterables withitertools.chain(*iterable_of_iterables).