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std::vector<std::vector<int>> vecOfVecs;
vecOfVecs.resize(10);
What will be positions 0-9 of vecOfVecs? Instances of std::vector?
If so, is this legitimate:
std::vector<int> *pToVec = &(vecOfVecs[0]);
pToVec->push_back(10);
The “canonical” definition of
std::vector::resizein C++03 actually has two parameters, not one, with the second argument being the element value that is used as a “fill value” for the freshly created elements. The second parameter has a default argument equal to a value-initialized object of element type. This means that your callis actually translated into a
call. I.e. it is actually you who implicitly supplied a default-constructed instance of
std::vector<int>to be used as an initializer for all new elements.Your
pToVec->push_back(10)call is perfectly legitimate.C++11 made some insignificant (in this context) changes to the definition of
resize, but the general effect remains the same: the new elements are value-initialized for you. They are ready to be used immediately after the call toresize.