Tree Hashing / Equivalence

Hi there,

Let's say I have a node type such as:

class Node {
     std::vector<Node> Children;
     std::string Value;
     int ID;
};

Are there any C++ libraries that could process a tree of such nodes and
calculate a hash value of some sort? Since I already depend on Boost, I
was hoping Boost.Graph provided an algorithm for something like this,
but I haven't found anything useful. Any other pointers?

The general idea is something like:

class Node {
     std::vector<Node> Children;
     std::string Value;
     int ID;

     size_t GetHash() const;
};

// Then:

int main() {
      Node root1 = ...; // Load from somewhere.
      Node root2 = ...; // Load from somewhere else.

      if (root1.GetHash() == root2.GetHash())
       ; // Trees are equivalent.
      else
          ; // Do some expensive work.

      return 0;
}

Thanks for your help!
-Al.

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