What's wrong with my turnary ? statement?

This is a discussion on What's wrong with my turnary ? statement? within the C++ Programming forums, part of the General Programming Boards category; Have a look at my code below. Code: #include <iostream> #include <cstdlib> using namespace::std; struct node { int data; struct ...

  1. #1
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    Thumbs up What's wrong with my turnary ? statement?

    Have a look at my code below.

    Code:
    #include <iostream>
    #include <cstdlib>
    using namespace::std;
    
    
    struct node {
    	int data;
    	struct node* left;
    	struct node* right;
    }; 
    
    void printInOrder(node* myNode);
    int countNodes(node* myNode);
    
    // a quick function to simulate a tree structure.
    struct node* getTree() {
    
    		// allocate space for six nodes.
    	struct node* root = new (struct node);
    	struct node* two = new (struct node);
    	struct node* three = new (struct node);
    	struct node* four = new (struct node);
    	struct node* five = new (struct node);
    	struct node* six = new (struct node);
    
    	root->data  = 1;
    		two->data   = 2;
    		three->data = 3;
    		four->data  = 4;
    		five->data  = 5;
    		six->data   = 6;
      
    	root->left = two;
    		root->right = three;
    		two->left = four;
    		two->right = five;
    		three->right = six;
    		return root;
    
    }
    
    
    int main() {
    	node *tree = getTree();
    	printInOrder(tree);
    	cout << "This tree has " << countNodes(tree) << " nodes." << endl;
    }
    
    void printInOrder(node* myNode){
    	if(myNode != 0){
    		printInOrder(myNode->left);
    		cout << myNode->data << endl;
    		printInOrder(myNode->right);
    	}	
    }
    
    int countNodes(node* myNode){
    	/*if(myNode != 0){
    		return (1 + countNodes(myNode->left) + countNodes(myNode->right));	
    	} else
    		return 0;*/
    	
    	//this is the statement in question
    	myNode != 0 ? return(1 + countNode(myNode->left) + countNode(myNode->right)) : return 0;
    }
    I know the syntax is correct because I checked it against another program I have that uses the operator and it works but this doesn't for some reason. My compiler tells me that it expects a primary expression before the return statement.
    Last edited by xmltorrent; 03-21-2006 at 12:27 PM.

  2. #2
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    The return should go at the head of the statement, followed by the comparison and then the value to return if true and the value to return if false. It is not like an if statement where you execute a command if the boolean expression is true. Instead the ternary expression only evaluates to a value depending on the boolean comparison. So you put the return in front so that you return that value.

  3. #3
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    Thanks for the help.

  4. #4
    and the hat of wrongness Salem's Avatar
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    Since ?: is just and if/else for expressions, you may as well save some confusion by writing
    Code:
    if ( myNode != 0 ) {
      return(1 + countNode(myNode->left) + countNode(myNode->right));
    } else {
      return 0;
    }
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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