c++ - An error: expected constructor, destructor, or type conversion before '(' token -

i getting error in *insert_nodes function:

error: expected constructor, destructor, or type conversion before '(' token

i have problem in same function, sais have redeclare 'int nodes' parameter in function. think it's not necessary write this:

*insert_nodes(start, int nodes) 

instead of being this:

*insert_nodes(start,nodes) 

another error in getch(). while compiling in netbeans, shows error on place doesn't mention type of error.

struct tree_traversal {     int data;     tree_traversal *left; //left subtree     tree_traversal *right; //right subtree };  tree_traversal *insert_nodes(tree_traversal *start, int nodes); void preordertraversal(tree_traversal *start); void postordertraversal(tree_traversal *start); void inordertraversal(tree_traversal *start); int counter = 1;  int main(int argc, char **argv) {     int choice, nodes;         {         switch(choice)         {              case 1:              cout<<"\n\t\a\a enter values:\a\a";              cin>>nodes;              start=insert_nodes(start,nodes);              break;               case 2:              cout<<"\n\t\a\a values in-order tree traversal is: \a\a"<<endl;              preordertraversal(start);              break;               case 3:              cout<<"\n\t\a\a values in-order tree traversal is: a\a"<<endl;              postordertraversal(start);              break;               case 4:              cout<<"\n\t\a\a values in-order tree traversal is: \a\a"<<endl;              inordertraversal(start);              break;               case 5:              exit(0);         }     } while(choice != 5);     return 0; }  tree_traversal *insert_nodes(tree_traversal *start, int nodes) {     if(start == null)     {         start = new tree_traversal;         start ->left = start ->right = null;         start ->data = nodes;         counter++;     }     else if(counter%2 == 0)         start ->left = insert_nodes(start ->left,nodes);     else         start ->right = insert_nodes(start ->right,nodes);      return(start); }  void preordertraversal(tree_traversal *start) {     if(start != null)     {         cout<<start ->data;         preordertraversal(start->left);         preordertraversal(start->right);         getch();     } }  void postordertraversal(tree_traversal *start) {     if(start != null)     {         postordertraversal(start->left);         postordertraversal(start->right);         cout<<start ->data;         getch();     } }  void inordertraversal(tree_traversal *start) {     if(start != null)     {         inordertraversal(start->left);         cout<<start ->data;         inordertraversal(start->right);         getch();     } } 

*insert_nodes(start, int nodes) 

should be

tree_traversal *insert_nodes(tree_traversal *start, int nodes) ^^^^^^^^^^^^^^^              ^^^^^^^^^^^^^^^ 

you forgot mention data type return type & function argument in function definition.

yes, need specify data types of function arguments in function definition.