STL vector reserve() and copy()
- by natersoz
Greetings,
I am trying to perform a copy from one vector (vec1) to another vector (vec2) using the following 2 abbreviated lines of code (full test app follows):
vec2.reserve( vec1.size() );
copy(vec1.begin(), vec1.end(), vec2.begin());
While the call to vec2 sets the capacity of vector vec2, the copying of data to vec2 seems to not fill in the values from vec1 to vec2.
Replacing the copy() function with calls to push_back() works as expected.
What am I missing here?
Thanks for your help. vectest.cpp test program followed by resulting output follows.
Compiler: gcc 3.4.4 on cygwin.
Nat
/**
* vectest.cpp
*/
#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector<int> vec1;
vector<int> vec2;
vec1.push_back(1);
vec1.push_back(2);
vec1.push_back(3);
vec1.push_back(4);
vec1.push_back(5);
vec1.push_back(6);
vec1.push_back(7);
vec2.reserve( vec1.size() );
copy(vec1.begin(), vec1.end(), vec2.begin());
cout << "vec1.size() = " << vec1.size() << endl;
cout << "vec1.capacity() = " << vec1.capacity() << endl;
cout << "vec1: ";
for( vector<int>::const_iterator iter = vec1.begin(); iter < vec1.end(); ++iter ) {
cout << *iter << " ";
}
cout << endl;
cout << "vec2.size() = " << vec2.size() << endl;
cout << "vec2.capacity() = " << vec2.capacity() << endl;
cout << "vec2: ";
for( vector<int>::const_iterator iter = vec2.begin(); iter < vec2.end(); ++iter ) {
cout << *iter << endl;
}
cout << endl;
}
output:
vec1.size() = 7
vec1.capacity() = 8
vec1: 1 2 3 4 5 6 7
vec2.size() = 0
vec2.capacity() = 7
vec2:
