Using a struct in a header file “unknown type” error

Question

I am using Kdevelop in Kubuntu. I have declared a structure in my datasetup.h file:

#ifndef A_H
#define A_H

struct georeg_val {

    int p;
    double h;
    do         


        

Answer 1

Defining a struct type (on this example, a binary search tree struct):

struct tree { 
  int info;
  struct tree *left;
  struct tree *right;
} 

typedef struct tree treeNode;

Declaring a function eg.:

treeNode *insertElement(treeNode *treeA, int number);