vector reserve() and clear()

[pkirk25]

vector<stringbu f_string;
buf_string.rese rve(256);
vector<intbuf_m at_prices;
buf_mat_prices. reserve(1000);

During loops I fill the vectors and then I empty them with commands
like buf_string.clea r();
buf_mat_prices. clear();

Does this mean that the memory allocation returns to default or is my
original reserve still in place?

[BobR]

pkirk25 wrote in message
<11************ **********@f16g 2000cwb.googleg roups.com>...

vector<stringbu f_string;
buf_string.rese rve(256);
vector<intbuf_m at_prices;
buf_mat_prices. reserve(1000);

During loops I fill the vectors and then I empty them with commands
like buf_string.clea r();
buf_mat_prices .clear();

Does this mean that the memory allocation returns to default or is my
original reserve still in place?

// Prove it for yourself: // using std::cout;
cout << buf_string.size () << std::endl; // S/B '0'
cout << buf_string.capa city() << std::endl; // clear() doesn't resize

cout << buf_mat_prices. size() << std::endl; // S/B '0'
cout << buf_mat_prices. capacity() << std::endl; // clear() doesn't
resize

You can re-size the vector by using (surprise!):

buf_string.resi ze(25);
cout << buf_string.size () << std::endl;
cout << buf_string.capa city() << std::endl;

That help?
--
Bob R
POVrookie

[pkirk25]

Very neat - many thanks! I didn't see the capacity member :-(

[Michiel.Salters]

pkirk25 wrote:

vector<intbuf_m at_prices;
buf_mat_prices. reserve(1000);
buf_mat_prices. clear();

Does this mean that the memory allocation returns to default or is my
original reserve still in place?

No, you still have the reservation. To "unreserve" you need to do a
swap-with-new:

vector<int>( ).swap(buf_mat_ prices).

The vector<int>( ) is a temporary that gets the 1000 reservation, and
then dies.
buf_mat_prices gets the capacity of the freshly constructed temporary.

HTH,
Michiel Salters