双端队列迭代器超出范围

Question

I am trying to shuffle through some array-like object. I want to add a value to the front, and then pop off the last value. I tried using deque as per suggestions I have seen to other posts but I am still getting errors. Any ideas? I am new to C++ and while I could try to write around this issue I would like to know where it is so I can fix it.

I am getting a: cannot seek deque iterator out of range debug error from visual studio.

The function that was causing problems:

(I was originally using vectors)

void vector_pusher(deque <int> &v, int new_val ) { 
v.push_front(new_val);
v.erase(v.begin() + 3);
}

Here is the rest of my code (maybe it's a constuctor issue?):

#include "lock.h"
#include <deque>
#include <iostream>
using namespace std;

lock::lock(int x, int y, int z) {
    is_closed = true;
    current_top = 0;
    comb[0] = x % MAX_VAL;
    comb[1] = y % MAX_VAL;
    comb[2] = z % MAX_VAL;
    deque <int> trycomb = { 1, 1, 1 };
    deque <char> trydir = { 'q', 'q', 'q' };
    deque <int> rot = { 1,1,1 };
}

void lock::turn(int input, char direction, int rotation) {

    vector_pusher(trydir, direction);
    vector_pusher(trycomb, input);
    vector_pusher(rot, rotation);

}

In lock.h:

 public:
        lock(int, int, int);
        void turn(int, char, int);
        \* these functions are defined elsewhere and doing fine
        void new_comb(int, int, int);
        void open_close();
        bool lock_status() const;
        *\

        //entered combination
        deque <int> trycomb;

        // entered diections
        deque <char> trydir;

        //entered rotations (0 is directly too, 1 is around once)
        deque <int> rot;



    private:
        // current correct combo
        deque <int> comb = {0, 0, 0};

        //top val
        //this is unessesary
        int current_top;

        //open-ness state of lock
        bool is_closed;

        //needed directions
        deque <char> dir = {'r', 'l', 'r'};

Thanks for the help!

Answer 1

It looks like you're never initializing trycomb , trydir , and rot in your constructor. You're declaring local variables in the constructor with the same name, which are shadowing the member variables of your lock class. Your constructor should look like this:

lock::lock(int x, int y, int z) {
    is_closed = true;
    current_top = 0;
    comb[0] = x % MAX_VAL;
    comb[1] = y % MAX_VAL;
    comb[2] = z % MAX_VAL;
    trycomb = { 1, 1, 1 };
    trydir = { 'q', 'q', 'q' };
    rot = { 1,1,1 };
}

Answer 2

As already mentioned you must change your constructor to

lock::lock(int x, int y, int z) {
    is_closed = true;
    current_top = 0;
    comb[0] = x % MAX_VAL;
    comb[1] = y % MAX_VAL;
    comb[2] = z % MAX_VAL;
    trycomb = { 1, 1, 1 };
    trydir = { 'q', 'q', 'q' };
    rot = { 1,1,1 };
}

otherwise the class members will not be initialized.

Secondly, you should use pop_front if you want to remove the first element in the queue and pop_back to remove the last element in the queue (see the documentation of deque). This makes the code much more readable.