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    <p>If your <code>mother</code> pointers point directly to elements of the <code>pieces</code> vector you will get in all kinds of trouble.</p> <p>Deleting an element from <code>pieces</code> will shift all the positions of the elements at higher indexes. Even inserting elements can make all the pointers invalid, since the vector might need to reallocate it's internal array which might transfer all the elements to new positions in memory.</p> <p>To answer your main question: You can't delete the element you have the pointer to directly, you would first need search through the vector to find it, or calculate it's index in the vector.</p> <p>Not storing pointers into <code>pieces</code> as <code>mother</code> but instead the indexes of the elements would make it a bit more robust, so that at least inserting new elements could not break the existing <code>mother</code>s. But deleting from <code>pieces</code> would still shift elements to new indexes.</p> <p>Using a <a href="http://www.cplusplus.com/reference/stl/list/" rel="nofollow noreferrer"><code>std::list</code></a> for <code>pieces</code> and storing iterators into that as <code>mother</code> might be a solution. Iterators of <code>std::list</code> are not invalidated if other elements are of that list are removed/added. If different elements can have the same <code>mother</code> you still have a problem finding out when to remove the <code>mother</code> elements, than maybe using <a href="http://www.boost.org/doc/libs/release/libs/smart_ptr/shared_ptr.htm" rel="nofollow noreferrer"><code>boost::shared_ptr</code></a> would be simpler.</p>
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    1. POC++ - Deleting a vector element that is referenced by a pointer
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    1. POC++ - Deleting a vector element that is referenced by a pointer
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    1. COActually, you *can* directly erase the element from the vector with "pieces.erase(the_piece.mother);" because the pointer is the same as the vector iterator to that piece. The main problem (invalidation) still exists, though, as pieces shift position in the vector.
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      1. USJason Govig
    2. CO@Jason: Yeah, that should usually be the case, but it's an implementation detail not really guaranteed by the vector class.
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    3. CO@sth: You are correct that it is an implementation detail. However, it is most likely that vectors are implemented as arrays and that their iterators are pointers. "Effective STL: 50 Specific Ways to Improve Your Use of the Standard Template Library" by Scott Meyers discusses how to pass vector data to a legacy (pointer-based) API, and he recommends &v[0] to get the pointer. Therefore, even if the iterator is not a pointer, you could at least use "mother - &pieces[0]" to get the index for erasure. However, both of these are techniques are something I'd avoid anyway ;)
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