Re: Initializing priority_queue in constructor

From:

"Alf P. Steinbach" <alfps@start.no>

Newsgroups:

comp.lang.c++

Date:

Sat, 26 Apr 2008 14:18:32 +0200

Message-ID:

<u6KdnanY8OsFgI7VnZ2dnUVZ_hqdnZ2d@comnet>

* Ray:

Hi all,

After many years of C, I thought I'd move to C++ recently. I think
because I think in C, I'm coming to a misunderstanding of something.

I've created a class foo which contains a private variable which is a
priority queue. In class foo's header file, I declared it as:

class foo {
private:
  unsigned int count;
  priority_queue<double, std::vector<double>, greater<double> >
pqueue;
};

In the constructor, I'm being warned that I should initialize in the
member initialization list (as I am new, I added all these warnings to
my compiler). So, I know I could do:

foo::foo ()
  : count (0)
{
}

but now I'm stuck. How does one initialize a priority queue? I want
to have a priority queue with nothing (i.e., empty) and it's already
done that for me in the declaration (I think...). Did I just get
myself in trouble by turning on the warnings and I should just ignore
this one about initializing pqueue? Obviously, this isn't an error
and I can continue...but I would like to know what should I do...

It's a good idea to post a minimal complete example.

As it is it's impossible to say what you're doing wrong.

The following compiles fine:

<code>
#include <iostream>
#include <queue>
#include <vector>

using namespace std;

class foo {
private:
     unsigned int count;
     priority_queue<double, std::vector<double>, greater<double> > pqueue;
public:
     foo();
};

foo::foo ()
   : count (0)
{
}

int main()
{
     foo o;
}
</code>

Cheers, & hth.,

- Alf

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