How do I code and pass a (reference to a std::vector)?

Question

I can't seem to get this right.

class Tree
{
    Node*   root;
    vector& dict;
} 

class Node
{
    vector& dict;
    char*   cargo;
    Node    left;
    Node    right;
}

I want each instance of Tree to have it's own dict, and I want it to pass a reference to the dict to the node constructor, which would recursively pass the reference to each child node so that each Node can enter a pointer to itself in the dict.

I'm having a lot of trouble with the syntax to:

get the vector initialized
pass a reference to the vector to the Node constructor
receive the reference in the Node constructor

I know this stuff is pretty basic. I'm teaching myself c++.

Thanks

`class Node { ... Node left; ... };` isn't going to work. You'll need to use a pointer for the `left` and `right` nodes. — James McNellis, Aug 08 '10 at 14:23
C++ references have nothing in common with Java/C# references. C#/Java references are more like pointers. — Billy ONeal, Aug 08 '10 at 14:33
Would using a "typedef vector& dict" simplify using this vector? — Peter Stewart, Aug 08 '10 at 17:39
Please get a [good book](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list), otherwise you're just going to hurt yourself. — GManNickG, Aug 08 '10 at 19:29

score 3 · Accepted Answer · answered Aug 08 '10 at 13:56

You haven't specified what you've tried that isn't working, but I suspect you are having trouble in the constructors because a reference can't be assigned to; you have to initialize it.

Also, when you use std::vector, you have to use a template parameter for the element type. So you can't just use vector&, you need vector<Something>&, where Something is whatever the element type is.

So, you probably want something like this:

class Tree
{
private:
    Node* root;
    std::vector<Something>& dict;

public:
    Tree(Node* aRoot, std::vector<Something>& aDict): root(aRoot), dict(aDict) {}
};

class Node
{
private:
    std::vector<Something>& dict;
    char*cargo;
    Node left;
    Node right;

    Node(std::vector<Something>& aDict, char* aCargo): dict(aDict), cargo(aCargo) {}
};

Aren't you missing a 'public:' in the Node class? – cschol Aug 08 '10 at 15:20 — cschol, Aug 08 '10 at 15:20

score 2 · Answer 2 · answered Aug 08 '10 at 13:55

2

You can initialize a reference only in an initialization list of a constructor. For instance,

Tree::Tree( vector<type>& d ) : dict(d) 
{
  ...
}

answered Aug 08 '10 at 13:55

Kirill V. Lyadvinsky

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How do I code and pass a (reference to a std::vector)?

2 Answers2

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