pointer question

[dschwart]

In the following procedure, I don't seem to understand how to specify the

ptr_to_tree -> ptr_to_left
ptr_to_tree -> ptr_to_right 

parameters

void Add(node ** ptr_to_tree, node * theNewNode) {
   if (*ptr_to_tree == 0)
      *ptr_to_tree = theNewNode;
   else
      if (theNewNode -> i  < (*ptr_to_tree) -> i)
         return Add( &ptr_to_tree -> ptr_to_left, theNewNode);   // ptr_to_tree
      else 
         return Add(ptr_to_tree -> ptr_to_right, theNewNode);  // ptr_to_tree
}

I call Add successfully (from main) with

node * a_new_node = (node *)malloc( sizeof(node) );
...
node * ptr_to_tree = 0;
...
Add(&ptr_to_tree, a_new_node);

Can someone kindly show me how ptr_to_tree -> ptr_to_right should be specified in

return Add(ptr_to_tree -> ptr_to_right, theNewNode);  // ptr_to_tree 

Thank you!

[D80DSL3A]

You got it right in the if statement on line 5:
(*ptr_to_tree) -> i deref the ** once, then again with -> to get the 'data' member.
Similarly, to obtain the 'pointer' members:
(*ptr_to_tree) -> ptr_to_right
Pass the address of this pointer to Add:
return Add( &(*ptr_to_tree) -> ptr_to_right, theNewNode);

[dschwart]

beauty, thanks