Can I create a for loop containing multiple type declarations?

For example:

Is there anything I can do, that might allow me to do this:

for(TiXmlElement * pChild = elem->First(), int i=0; // 开发者_运维百科note multiple type declarations
    pChild; 
    pChild=pChild->NextSiblingElement(), i++) // note multiple types
{
    //do stuff
}

Perhaps there is a boost header?

Nope.

If you want to limit the scope of variables to the loop just add another scope:

{
    TiXmlElement * pChild = elem->First();
    int i = 0;
    for(; pChild; pChild=pChild->NextSiblingElement(), i++)
    {
        //do stuff
    }
}

Blocks do not have to be attached to functions or conditionals. You can surround any piece of code with a block to limit the scope of temporary variables to that block.

{
    TiXmlElement * pChild;
    int i;
    for ( pChild = elem->First(), i = 0;
          pChild;
          pChild = pChild->NextSiblingElement(), ++i )
    {
        // do stuff
    }
}

Since C++17, introducing multiple variables is possible with structured bindings:

// multiple type declarations
for (auto [pChild, i] = std::tie(elem->First(), 0); pChild; pChild = pChild->NextSiblingElement(), ++i) {
    // ...
}

pChild is a TiXmlElement*, and i is an int, as expected.