vector<bool>::operator

Returns a simulated reference to the vector<bool> element at a specified position.

vector<bool>::reference operator[](
   size_type Pos
);
vector<bool>::const_reference operator[](
   size_type Pos
) const;

Parameters

Return Value

A vector<bool>::reference or vector<bool>::const_reference object that contains the value of the indexed element.

If the position specified is greater than or equal to the size of the container, the result is undefined.

Remarks

If you compile with _ITERATOR_DEBUG_LEVEL set, a run-time error occurs if you attempt to access an element outside the bounds of the vector. For more information, see Checked Iterators.

Example

This code example shows the correct use of vector<bool>::operator[] and two common coding mistakes, which are commented out. These mistakes cause errors because the address of the vector<bool>::reference object that vector<bool>::operator[] returns cannot be taken.

// cl.exe /EHsc /nologo /W4 /MTd 
#include <vector>
#include <iostream>

int main()
{
    using namespace std;
    cout << boolalpha;
    vector<bool> vb;

    vb.push_back(true);
    vb.push_back(false);

    //    bool* pb = &vb[1]; // conversion error - do not use
    //    bool& refb = vb[1];   // conversion error - do not use
    bool hold = vb[1];
    cout << "The second element of vb is " << vb[1] << endl;
    cout << "The held value from the second element of vb is " << hold << endl;

    // Note this doesn't modify hold.
    vb[1] = true;
    cout << "The second element of vb is " << vb[1] << endl;
    cout << "The held value from the second element of vb is " << hold << endl;
}

Output

The second element of vb is false
The held value from the second element of vb is false
The second element of vb is true
The held value from the second element of vb is false

Requirements

Header: <vector>

Namespace: std

See Also

Reference

vector<bool> Class

Standard Template Library