2010/5/28 Cliff Green
Resize can trim the vector and I don't want it. I think "reserve" is the right function for my need.
When I use push_back instead of operator[] there is no pb.
As Ion is probably just pointing out, there's a fundamental difference between resize and reserve. Resize modifies the "logical size" of the container, creating (by default construction) new entries, or removing (with destruction) entries. Reserve does not change the "logical size", and it's only use is as an implementation optimization (you can pre-assign internal buffer space, so that when adding new entries later on a memory allocation will already have occurred).
For a vector, you can create one and then reserve one all you want, but the size is still 0 (until "push_back" or "insert", etc is performed), and indexing into the vector will be out of bounds.
Read Josuttis C++ standard library book, or any good reference on the difference.
Cliff
Ok, so I't my fault ;) I use mainly online reference (sgi.com and cplusplus.com ) and the fact that reserve() does not initialize memory is not so obvious in these docs. So thank you for your help. Gaetan.