Question

This is a bizarre problem. I’ve got a void function that performs a for loop and nothing else, but the for loop doesn’t ever start, even though the function is being called. Here is the function:

void Cell::Consolidate()
{
    cout << "Consolidating (outside)...\n";
    for(int i = 0; i < m_Tiles.size(); ++i)
    {
        cout << "Consolidating (inside)...\n";
        int row = m_Tiles[i]->GetRow();
        int col = m_Tiles[i]->GetCol();
        //Check below.
        if((*m_pTileMap)[row + 1][col].pParentCell != this)
        {
            m_EdgeTiles.push_back(m_Tiles[i]);
            m_Tiles[i]->SetColor(sf::Color(100, 100, 100));
            bool newNeighbor = true;
            for(int j = 0; j < m_Neighbors.size(); ++j)
            {
                if(m_Neighbors[j] == (*m_pTileMap)[row + 1][col].pParentCell)
                {
                    newNeighbor = false;
                    break;
                }
            }
            if(newNeighbor)
            {
                m_Neighbors.push_back((*m_pTileMap)[row + 1][col].pParentCell);
            }
        }
        //Check above.
        else if((*m_pTileMap)[row - 1][col].pParentCell != this)
        {
            m_EdgeTiles.push_back(m_Tiles[i]);
            m_Tiles[i]->SetColor(sf::Color(100, 100, 100));
            bool newNeighbor = true;
            for(int j = 0; j < m_Neighbors.size(); ++j)
            {
                if(m_Neighbors[j] == (*m_pTileMap)[row - 1][col].pParentCell)
                {
                    newNeighbor = false;
                    break;
                }
            }
            if(newNeighbor)
            {
                m_Neighbors.push_back((*m_pTileMap)[row - 1][col].pParentCell);
            }
        }
        //Check the right.
        else if((*m_pTileMap)[row][col + 1].pParentCell != this)
        {
            m_EdgeTiles.push_back(m_Tiles[i]);
            m_Tiles[i]->SetColor(sf::Color(100, 100, 100));
            bool newNeighbor = true;
            for(int j = 0; j < m_Neighbors.size(); ++j)
            {
                if(m_Neighbors[j] == (*m_pTileMap)[row][col + 1].pParentCell)
                {
                    newNeighbor = false;
                    break;
                }
            }
            if(newNeighbor)
            {
                m_Neighbors.push_back((*m_pTileMap)[row][col + 1].pParentCell);
            }
        }
        //Check the left.
        else if((*m_pTileMap)[row][col - 1].pParentCell != this)
        {
            m_EdgeTiles.push_back(m_Tiles[i]);
            m_Tiles[i]->SetColor(sf::Color(100, 100, 100));
            bool newNeighbor = true;
            for(int j = 0; j < m_Neighbors.size(); ++j)
            {
                if(m_Neighbors[j] == (*m_pTileMap)[row][col - 1].pParentCell)
                {
                    newNeighbor = false;
                    break;
                }
            }
            if(newNeighbor)
            {
                m_Neighbors.push_back((*m_pTileMap)[row][col - 1].pParentCell);
            }
        }
    }
}

When I run the program, "Consolidating (outside)...\n" gets send to cout, but "Consolidating (inside)...\n" does not. Nothing that is supposed to happen in the loop actually happens, either (for example the SetColor() calls don’t do anything, nor does anything happen if I send things to cout anywhere else in the loop), so I can only assume the loop is not starting at all. Why not? What could cause this?

Answer 1

i < m_Tiles.size()

This loop condition gets checked on entrance to the loop, not only after each iteration. If your m_Tiles vector is empty, well, no loop for you.