How should I pass this std::array<> to a function?

Question

std::array<LINE,10> currentPaths=PossibleStrtPaths();
LINE s=shortestLine(currentPaths);                       //ERROR

---

LINE CShortestPathFinderView::shortestLine(std::array<LINE,10> *currentPaths)
{
std::array<LINE,10>::iterator iter;

LINE s=*(currentPaths+1);                      //ERROR

for(iter=currentPaths->begin()+1;iter<=currentPaths->end();iter++)
{
     if(s.cost>iter->cost)
     s=*iter;
}

std::remove(currentPaths->begin(),currentPaths->end(),s);

    //now s contains the shortest partial path  
return s; 


}

At both those statements I'm getting the same error: no suitable conversion from std::array<LINE,10U>*currentPaths to LINE . Why is this so? Should I pass the array another way? I've also tried passing currentPaths as a reference, but it tells me that a reference of the type cannot be initialized.

Answer 1

You said you tried a reference and it failed. I don't know why, because that was the correct thing to do.

LINE CShortestPathFinderView::shortestLine(std::array<LINE,10> &currentPaths);

From the sounds of it, you also used a reference for the temporary variable. That's wrong.

std::array<LINE,10>& currentPaths = PossibleStrtPaths(); // WRONG
std::array<LINE,10>  currentPaths = PossibleStrtPaths(); // RIGHT
LINE s = shortestLine(currentPaths);

And finally, the first element is number zero. The subscripting operator [] is preferred when you are doing array access. So:

LINE s = currentPaths[0];

But you also can easily get the first item from the iterator.

Final code:

/* precondition: currentPaths is not empty */
LINE CShortestPathFinderView::shortestLine(std::array<LINE,10>& currentPaths)
{
    std::array<LINE,10>::iterator iter = currentPaths.begin();
    LINE s = *(iter++);

    for(; iter != currentPaths->end(); ++iter) {
       if(s.cost>iter->cost)
          s=*iter;
    }

    std::remove(currentPaths.begin(), currentPaths.end(), s);

    //now s contains the shortest partial path  
    return s;
}

Answer 2

您正在取消引用(currentPaths+1) ，其类型为std::array* （更准确地说：您是在递增指针，然后访问其指向的数据），而您可能想检索currentPaths的第一个元素，即： currentPaths[0] （数组中的第一个索引为0）。