Queue is not a member of std in C++

Introduction

The std::queue function is a highly useful function that allows us to create and manipulate first-in-first-out (FIFO) queues in the C++ programming language. However, we can often get errors from the compiler such as:

error: ‘queue’ is not a member of ‘std’

This error is pretty straight-forward to fix as we will see below.

Potential causes

The queue is not a member of std error could be caused by multiple reasons.

Fix #1: Add queue to your dependencies

Essentially, the std::queue function needs to have access to the queue module in order to be executed by the compiler.

Therefore, you must add the following #include header to the top of your code (in the include(s) part) such as:

#include <queue> //Add this

int main() {
    std::queue<int> myQueue;
    myQueue.push(1);
    return 0;
}

The compiler should now recognize the std::queue function, thus fixing the queue is not a member of std error.

Fix #2: Using namespace std

Note that we have previously typed: std::queue instead of queue. We can type “queue” only if we are declaring that we are using its namespace.

In other words, we would need to type “using namespace std” in the header if we only want to type queue (which is obviously shorter) instead of std::queue. For instance, we can have something like:

#include <queue>
using namespace std; //Add this

int main() {
    queue<int> myQueue;
    myQueue.push(1);
    return 0;
}

It is okay to type std::queue without typing “using namespace std”. In fact, it is generally recommended to type the full std::queue function name (and therefore avoiding using namespace std) when working with multiple libraries because it can reduce future confusion.

However, if you still want to type “queue” instead of std::queue, then you need to add “using namespace std” to the header

References

Read more about the std::queue function here: https://www.cplusplus.com/reference/queue/queue/