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const_reference at ( size_type n ) const;
reference at ( size_type n );
Access element
Returns a reference to the element at position n in the vector.
The difference between this member function and member operator function operator[] is that vector::at signals if the requested position is out of range by throwing an out_of_range exception.
Parameters
- n
- Position of an element in the vector.
If this is greater than or equal to the vector size, an exception of type out_of_range is thrown.
Notice that the first element has a position of 0, not 1.
Member type size_type is an unsigned integral type.
Return value
The element at the specified position in the vector.
Member types reference and const_reference are the reference types to the elements of the vector container (for the default storage allocation model, allocator, these are T& and const T& respectively).
Example
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// vector::at
#include <iostream>
#include <vector>
using namespace std;
int main ()
{
vector<int> myvector (10); // 10 zero-initialized ints
unsigned int i;
// assign some values:
for (i=0; i<myvector.size(); i++)
myvector.at(i)=i;
cout << "myvector contains:";
for (i=0; i<myvector.size(); i++)
cout << " " << myvector.at(i);
cout << endl;
return 0;
}
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Output:
myvector contains: 0 1 2 3 4 5 6 7 8 9
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Complexity
Constant.
See also
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