Question

I’ve written 2 classes (AVL and Stack for my Data Structures lecture) and I’m trying to call this function:

int MyStack::Push(avlnode *x)

in a function of the AVL class:

trace.Push(temp);

trace is a MyStack object
and temp a pointer to avlnode (which is a struct).

When I try to compile the code I get the following error:

In member function 'int MyAVLTree::Insert(int)':
error: no matching function for call to 'MyStack::Push(MyAVLTree::avlnode*&)'
note: candidates are: int MyStack::Push(avlnode*)|

Answer 1

I can reproduce your error with the snippets provided further down in this post.

My guess is that you’ve put a forward declaration in the wrong place, probably in the global scope near MyStack (so that you can use it inside of the mentioned class).

class avlnode;

struct MyStack {
  int Push (avlnode *) {return 0;} 
};

…

struct MyAVLTree {
  struct avlnode {
    /* ... */
  };

  MyAVLTree (MyStack& a)
    : a (a) 
  {}  

  int insert (int) {
    avlnode * p; a.Push (p);
    return 0;
  }

  MyStack& a;
};

…

int main(int argc, char* argv[])
{
  MyStack   a;  
  MyAVLTree b (a);

  b.insert (123);
}

…

foo.cpp: In member function 'int MyAVLTree::insert(int)':
foo.cpp:20:27: error: no matching function for call to 'MyStack::Push(MyAVLTree::avlnode*&)'
foo.cpp:20:27: note: candidate is:
foo.cpp:9:7: note: int MyStack::Push(avlnode*)
foo.cpp:9:7: note:   no known conversion for argument 1 from 'MyAVLTree::avlnode*' to 'avlnode*'