Removing the first element from a queue?

Question

I have a queue. If it exceeds X size, when I push an element I want to remove the first element of the queue. (the last element that would get popped and the first element pushed in)

void ClientPlayerManager::queueTableMessage( const std::string& playerName, const std::string& message )
{
    m_tableQ.push(std::make_pair(playerName,message));

    if(m_tableQ.size() > m_maxTableMessages)
    {
        //m_tableQ.pop_back(); does not exist
    }
}

Is there a way to do this with a std queue?

Thanks

In a FIFO queue, the last element that would get popped is at the opposite end from the first element pushed in. Which do you want? — Ben Voigt
– Ben Voigt, Commented May 29, 2012 at 19:20
Yes, it's quite confusing. Why not just use push and pop and forget about it? — Niklas B.
– Niklas B., Commented May 29, 2012 at 19:21

templatetypedef · Accepted Answer · 2012-05-29 19:19:14Z

6

You can use a std::deque instead of a std::queue, which supports push_front, push_back, pop_front, and pop_back. This also allows for random access throughout, but you can just ignore that and treat the deque like a double-ended queue. (In fact, deque is short for double-ended queue).

Hope this helps!

answered May 29, 2012 at 19:19

templatetypedef

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Comments

Ben Voigt · Accepted Answer · 2012-05-29 19:22:27Z

0

If you want to remove an element from the opposite end from what pop does, just skip pushing it in the first place:

if(m_tableQ.size() < m_maxTableMessages) {
    m_tableQ.push(std::make_pair(playerName,message));
}

answered May 29, 2012 at 19:22

Ben Voigt

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2 Comments

jmasterx Over a year ago

No, the idea is that I want the top X messages to stay, when I have X messages, the one of least importance (the oldest one) goes and a new one is in.

Ben Voigt Over a year ago

@Milo: In that case, you can just use pop.

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