C++ priority_queue doesn't have push?

Question

I have these at the top of my file:

#include <queue>

typedef struct cell_s {
    unsigned int x;
    unsigned int y;
    unsigned int ambiguity = 9;
} cell_t;

// so the priority_queue can sort the structs:
bool operator<(const cell_t &a, const cell_t &b) {
    return a.ambiguity < b.ambiguity;
}

In the same file I have declared a priority_queue as a private member of a class, like this:

priority_queue<cell_t> blankCellQueue;

Then I have a member function of the same class that contains these lines:

cell_t cell;
cell.x = x;
cell.y = y;
blankCellQueue.push(cell);

But Xcode is presenting this warning on the last line I shared:

"No matching member function for call to 'push'".

Answer 1

priority_queue is part of the namespace, std . You need to use std::priority_queue .

Answer 2

C++11's std::priority_queue is a standard container adapter and it does have member function push() - see the linked reference.

It is possible, though, that your implementation of the C++ Standard Library is not compliant. You should upgrade to the latest version.

You can see your code compiling here . It required adding the std:: namespace qualifier before priority_queue , but I do not believe that to be the root cause of the issue here. If it were, your compiler error should be different (or you should receive other errors before).

Answer 3

Sorry to have wasted all of your time. I found the issue. The priority_queue is a member of my class. The function I was attempting to edit the priority_queue from was a member function that I had marked as const, because I hadn't anticipated a need to modify any class variables when I originally wrote it without any queue. Invoking push on a member object from a const member function is an obvious no-no. I just wish Xcode had given a slightly useful error messages... something along the lines of "non const function invoked from const function" would be a very helpful message.

Since I hadn't provided the member function declaration, it would have been very difficult for anyone to have pointed that out to me here.

Thanks for the offers of help!