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    <p>This is not really a good idea, but I'll show you how.</p> <p>You can get a raw pointer to the integer this way:</p> <pre><code>int * myPointer2 = (int*)&amp;(s[0]); </code></pre> <p>but this is really bad practice because you can't guarantee that the span structure doesn't have any <a href="http://en.wikipedia.org/wiki/Data_structure_alignment" rel="nofollow noreferrer">padding</a>, so while it might work fine for me and you today we can't say much for other systems.</p> <pre><code>#include &lt;iostream&gt; #include &lt;vector&gt; struct Span{ int from; int to; }; int main() { std::vector&lt;Span&gt; s; Span a = { 1, 2}; Span b = {2, 9}; Span c = {10, 14}; s.push_back(a); s.push_back(b); s.push_back(c); int * myPointer = (int*)&amp;(s[0]); for(int k = 0; k &lt; 6; k++) { std::cout &lt;&lt; myPointer[k] &lt;&lt; std::endl; } return 0; } </code></pre> <p>As I said, that hard reinterpret cast will often work but is very dangerous and lacks the cross-platform guarantees you normally expect from C/C++.</p> <p>The next worse thing is this, that will actually do what you asked but you should never do. This is the sort of code you could get fired for:</p> <pre><code>// Baaaad mojo here: turn a vector&lt;span&gt; into a vector&lt;int&gt;: std::vector&lt;int&gt; * pis = (std::vector&lt;int&gt;*)&amp;s; for ( std::vector&lt;int&gt;::iterator It = pis-&gt;begin(); It != pis-&gt;end(); It++ ) std::cout &lt;&lt; *It &lt;&lt; std::endl; </code></pre> <p>Notice how I'm using a pointer to vector and pointing to the address of the vector object s. My hope is that the internals of both vectors are the same and I can use them just like that. For me, this works and while the standard templates may luckily require this to be the case, it is not generally so for templated classes (see such things as padding and template specialization).</p> <p>Consider instead copying out an array (see ref 2 below) or just using s<a href="http://en.wikipedia.org/wiki/Data_structure_alignment" rel="nofollow noreferrer">1</a>.from and s[2].to.</p> <p>Related Reading:</p> <ol> <li><a href="https://stackoverflow.com/questions/849168/are-stdvector-elements-guaranteed-to-be-contiguous">Are std::vector elements guaranteed to be contiguous?</a></li> <li><a href="https://stackoverflow.com/questions/2923272/how-to-convert-vector-to-array-c">How to convert vector to array in C++</a></li> </ol>
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    1. POC++ cast vector type in place
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    1. CO+1: I mucked around in my VBox trying this but I didn't think of casting to pointers and then back. This kind of trick seems more like something you'd find/hack out in C, and as you pointed out it's really quite dangerous. A really good answer ^^
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    2. COI think a "better" idea would be to cast to a pointer to array of 2 elements: `reinterpret_cast<int(*)[2]>(&s[0]);`, and access the individual members with the subscript operator. However, I think this is stll horrifically undefined behaviour right there.
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    3. CO@R.MartinhoFernandes Yes, Windows 7 64bit, Intel 2600k, Visual Studio 2008 9.0.30729.1 SP
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