[boost] Re: graph structure interface compomise?

From: Gabriel Dos Reis (dosreis_at_[hidden])
Date: 1999-12-09 00:36:48

jsiek_at_[hidden] writes:

[...]

|  > Personally, I would prefer if there were separate functions to get the
|  > respective iterator, especially as C++ misses such neat assignment
|  > operations as there are in perl where you can assign to a list of
|  > objects at once (well, I think there was a library for this mentioned
|  > somewhere; was it Boost or have seen it in news: I don't know). Is
| 
| Yes, it was posted to Boost. I like it. Here's how it would look with
| the graph interface:
| 
| tie(first,last) = adj(v,g);
| 
| A dumbed-down, two argument version is trivial to implement:
| 
| template <class A, class B>
| class Tie
| {
| public:
|   Tie(A a, B b) : first(a), second(b) { }
|   template <class Pair>
|   Tie& operator=(const Pair& p) {
|     first = p.first;
|     second = p.second;
|   }
| protected:
|   A first;
|   B second;
| };
| 
| template <class A, class B>
| Tie<A&,B&> tie(A& a, B& b) {
|   return Tie<A&,B&>(a,b);
    ^^^^^^^^^^^^^^^^^^^^^^

I'm not sure if the synthetised copy-ctor is guaranted to do the right
thing here.

| }

Why not just 

        template<typename A, typename b>
        class tie {
        public:
                tie(A& a, B& b) : first(a), second(b) {}
                
                template<typename Pair>
                tie& operator=(const Pair& p)
                {
                        first = p.first;
                        second = p.second;
                }

        private:
                A& first;
                B& second;
        };

That is the constructor function-call syntax does the right thing.

-- Gaby