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The other iterator types surely don't have the implication that they point to continuous data, but I'm wondering if I can treat RandomAccessIterators as if they point to a buffer of continuous data – i.e. they could be converted to pointers to data.

Is this assumption correct? Can I always safely use &*it and get a pointer not just to one element, but to a continuous buffer, if it is a RandomAccessIterator?

Felix Dombek
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1 Answers1

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No, it is not a valid assumption. The standard library itself has a counterexample in std::deque:

from cppreference:

As opposed to std::vector, the elements of a deque are not stored contiguously: typical implementations use a sequence of individually allocated fixed-size arrays.

std::deque's iterator is a RandomAccessIterator:

[deque.overview]/1

A deque is a sequence container that, like a vector ([vector]), supports random access iterators.

If you want a guarantee of contiguous memory, you don't need to wait long: the guarantee will be provided by the ContiguousIterator in C++17.1

the ContiguousIterator concept was proposed in a sequence of documents ending in N4284, and adopted in November 2014

jaggedSpire
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  • It worth mentionong that C++17 will add `ContiguousIterator` category. – Revolver_Ocelot Jun 08 '16 at 15:34
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    [This is what I found](https://isocpp.org/blog/2014/11/new-standard-library-papers-adopted-for-cpp17). Sadly, it only a concept which gives guarantees to certain containers, it didn't add corresponding tag, as it apparently broke code. – Revolver_Ocelot Jun 08 '16 at 15:53
  • unfortunately, `ContiguousIterator` in C++17 has no practical use https://stackoverflow.com/a/52277825/8414561 – Dev Null Sep 11 '18 at 23:41