Question

I have deque and want to iter it backwards. I also need the index (otherwise I’d use the reverse_iterator) so I tried:

if ( _children.size( ) > 0 ) // debugging purpose
{
    unsigned si( _children.size( ) ); // debugging purpose
    int s( _children.size( ) - 1 ); // debugging purpose
    for ( unsigned c ( 0 ) ; c < _children.size( ) ; ++c )
        if ( this->_children[ ( _children.size( ) - 1 ) - c ]->Topmost( ) && 
             this->_children[ ( _children.size( ) - 1 ) - c ]->BorderRectangle( ).IsIn( X , Y ) )
               return std::pair< int, WindowPointer >( ( _children.size( ) - 1 ) - c, this->_children[ ( _children.size( ) - 1 ) - c ]->WindowAt( x, y ) );

but I get a sigsev. After debugging I get that index was -65. I checked the _children.size( ) by

unsigned si = _children.size( );

and it is 4294967232. And

long s = _children.size( ) - 1;

is -65. How do I get such values? And how to fix this?

Answer 1

You should use the reverse_iterator. If you want to keep track of an index, you can add a variable to your for loop like this:

int counter = 0;
for (xx::reverse_iterator it = yy.rbegin(); it != yy.rend(); ++it, ++counter) {
    // Do something
}

This is les error-prone than what you are doing.