Rust iterators are more limited than cursors. Random access falls outside of Rust's concept of iteration. It's not the same as doing i += 10 for a "random access iterator" in C++.
But this is still fundamentally iteration, so calling nth(10) should have the same effect as calling next() 11 times and just discarding the first 10 values. That doesn't mean you can't do a lot of the same stuff with iterators that you can with cursors! For instance, you can skip an item in the sequence by calling next() without using the value it returns, or you can skip a bunch of items by using nth(10). But the idea of an iterator is an object that can produce things from a sequence one at a time. The sequence can be anything, like "all the odd numbers from 1 to 1000 in increasing order" or "ten million random strings" or "just the number 0.04, repeated forever". An iterator is just something that produces items from a sequence one at a time. Rust's iterators are firmly grounded in iteration. All these things are reasonable to do in a cursor-based API, but they don't really have anything to do with iteration. Some cursors can move instantly to any other position in the range without moving through the intermediate positions (C++ calls these "random access iterators"). Cursors may also be moved backward as well as forward (C++ calls these "bidirectional iterators"). You can advance a cursor by several steps at a time, skipping some values, or you can follow (dereference) the cursor several times without advancing it, processing the same value more than once. You can use a cursor to iterate over a range, but that's not all you can do. We could call it a cursor.Ĭursors are in a sense a lower-level abstraction than iterators. Basically it represents a position in a range. It usually looks something like this: for (c = begin() c != end() ++c) Ĭ could be a pointer, but it might also be an integer. When you want to iterate over something, you write a loop. C++ is really an odd duck when it comes to iterators, so you may have a bit to unlearn.Ĭ++ is based on C, and in C there is no such thing as an iterator.
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