make_heap comparison

Hi there.

I want to turn a vector of structures in a heap. I'm trying to use make_heap function, from STL which have the following constructor:

Code:

---

template <class RandomAccessIterator, class Compare>
void make_heap(RandomAccessIterator first, RandomAccessIterator last, Compare comp);

---

I realy need to build that comp class so I can compare those structure's fields but I realy don't know how. I've searched a lot and didn't find anything useful about that Compare class.

Can anyone teach me how to build one?

Thank you for any help.

Regards.

The are two versions of make_heap: one uses the operator< of your class, the other allows you to specify a comparator. "Compare" is just the placeholder for the name of your function or function object. Likewise, "RandomAccessIterator" is just a placeholder telling you that the first two arguments take a random access iterator, be it a pointer or the iterator returned by the begin() and end() member functions of a vector.

So, if you already have an operator< that makes sense in this context, then use that version of make_heap that has only two arguments. If you do not want to use operator<, then you may try a function object, e.g.,

Code:

---

class CompareFoo
{
public:
    // Compare two Foo structs.
    bool operator()(const Foo& x, const Foo& y) const
    {
        return x.bar < y.bar;
    }
};

// Create an instance of CompareFoo to use in comparision.
make_heap(v.begin(), v.end(), CompareFoo());

---

Thanks, that really helped. :)

Regards.