Simple use of priority queue

[Paul]

Suppose I have

bool f(int lhs, int rhs)
{
///
}

std::vector<int> vec;

// vec is further set here.

What is the simplest way to set a priority_queue with the elements in vec based on the order defined by f?

Thank you,

Paul

[Öö Tiib]

Simplest to me feels to try to type the sentence above in C++:

std::priority_queue<int, std::vector<int>, decltype(&f)> pq( &f, vec );

Was it what you asked?

[Paul]

Yes, that's what I asked. Thanks.

Paul

[Paul]

On Monday, August 10, 2015 at 10:28:32 AM UTC+1, Öö Tiib wrote:

Is the below also ok? Is this a context in which the type of a function is understood to be the function pointer?

Thank You,

Paul
std::priority_queue<int, std::vector<int>, decltype(f)> pq( f, vec );

[Öö Tiib]

No. It can't work ... you need a function pointer not function.
The 'decltype' is keyword not function and looseness in its argument does
not work.

Following variants must work:

std::priority_queue<int, std::vector<int>, decltype(&f)> pq( &f, vec );

std::priority_queue<int, std::vector<int>, decltype(&f)> pq( **f, vec );

That looseness with function (or on current case constructor) function
pointer arguments is perhaps inherited from C ... I have forgot its history.