[Boost-users] Tips on implementing a function queue with unique queue items (compare function problem)

Subject: [Boost-users] Tips on implementing a function queue with unique queue items (compare function problem)
From: Peter Åberg (aberg_at_[hidden])
Date: 2009-05-12 08:46:26

Hi,

Anyone have a tip or pointer regarding how to implement a function queue 
with unique items?

Comparing C++ delegates seems to be hard in general 
(http://www.boost.org/doc/libs/1_39_0/doc/html/function/faq.html#id1877737) 
but there are probably workarounds that are alright. It would be nice of 
course if the queue user stays unaffected by the workaround but that is 
probably not possible. Another layer perhaps.
Any suggestion for the code below?

class UniqueFunctionQueue
{
public:
    typedef boost::function<void()> QueueItem;

public:
    void push(QueueItem item)
    {
        /* ToDo, would be nice to do:
        if (item is already in the queue)
            return;
        */
        queue.push_back(item);
    }
    void execute()
    {
        for(std::deque<QueueItem>::iterator i = queue.begin(); i != 
queue.end(); i++)
            (*i)();
        queue.clear();
    }

private:
    std::deque<QueueItem> queue;
};

....

UniqueFunctionQueue queue;
queue.push(boost::bind(&Synchronizer::sync, &synchronizer, LeftToRight));
queue.push(boost::bind(&Synchronizer::sync, &synchronizer, RightToLeft));
queue.push(boost::bind(&Initializer::init, &initializer));
queue.push(boost::bind(&Synchronizer::sync, &synchronizer, 
LeftToRight)); // Should not be added since there is one in the queue 
already.
queue.execute();

Thanks,
Peter Åberg