Which c++ container can contain C int multidimensional arrays (C++03/MSVC11)?

Question

I have this multidimensional 2 arrays

int anArray1[MAX_ROW][MAX_CELL] =
{
    { 0, 1, 1, 0, 1, 1, 1, 0},
    { 0, 1, 1, 0, 1, 1, 1, 0},
    { 0, 1, 1, 0, 1, 1, 1, 0},
    { 0, 1, 1, 0, 1, 1, 1, 0},
    { 0, 0, 0, 0, 0, 0, 0, 0}
}


int anArray2[MAX_ROW][MAX_CELL] =
{
    { 0, 1, 1, 0, 1, 1, 1, 0},
    { 0, 1, 1, 0, 1, 1, 1, 0},
    { 0, 1, 1, 0, 1, 1, 1, 0},
    { 0, 1, 1, 0, 1, 1, 1, 0},
    { 0, 0, 0, 0, 0, 0, 0, 0}
}

and i want to store them in index based container , i tryed to make another int array that supposed to hold them like this:

int LevelsArray[LEVELS_COUNT] = { anArray1, anArray2};

im getting this error:

error C2440: 'initializing' : cannot convert from 'int [68][8]' to 'int'

i guess this is not the correct way .. what is the recommended way ?

They aren't ints. Try making a typedef of the array and an array of that. — Neil Kirk
– Neil Kirk, Commented Feb 2, 2015 at 7:41
Short answer: none. Longer answer: it may be possible to instantiate a container of arrays, but you won't be able to do anything useful with it. — juanchopanza
– juanchopanza, Commented Feb 2, 2015 at 8:07

Community · Accepted Answer · 2017-05-23 10:26:49Z

5

I wouldn't consider a plain old array a C++ container. I would rather use a combination of std::vector (or std::array), because of reasons.

Here's an example:

#include <iostream>
#include <vector>

typedef int cell;
typedef std::vector<cell> row;
typedef std::vector<row> level;
typedef std::vector<level> levels;

int main() {
    levels l = 
    {
        {
            { 0, 1, 1, 0, 1, 1, 1, 0},
            { 0, 1, 1, 0, 1, 1, 1, 0},
            { 0, 1, 1, 0, 1, 1, 1, 0},
            { 0, 1, 1, 0, 1, 1, 1, 0},
            { 0, 0, 0, 0, 0, 0, 0, 0}
        },
        {
            { 0, 1, 1, 0, 1, 1, 1, 0},
            { 0, 1, 1, 0, 1, 1, 1, 0},
            { 0, 1, 1, 0, 1, 1, 1, 0},
            { 0, 1, 1, 0, 1, 1, 1, 0},
            { 0, 0, 0, 0, 0, 0, 0, 0}
        },
    };
    for (int i = 0; i < l.size(); i++) {
        std::cout << "level " << i << ":\n" ;
        for (row & r : l[i]) {
            for (cell & c : r)
                std::cout << c << " ";
            std::cout << "\n";
        }
        std::cout << "\n";
    }
}

The output is:

$ g++ test.cc -std=c++11 && ./a.out
level 0:
0 1 1 0 1 1 1 0 
0 1 1 0 1 1 1 0 
0 1 1 0 1 1 1 0 
0 1 1 0 1 1 1 0 
0 0 0 0 0 0 0 0 

level 1:
0 1 1 0 1 1 1 0 
0 1 1 0 1 1 1 0 
0 1 1 0 1 1 1 0 
0 1 1 0 1 1 1 0 
0 0 0 0 0 0 0 0

Using std::array instead could look something like this:

#include <iostream>
#include <vector>
#include <array>

const int cells_per_row = 8;
const int rows_per_level = 5;
const int nlevels = 2;
typedef int cell;
typedef std::array<cell, cells_per_row> row;
typedef std::array<row, rows_per_level> level;
typedef std::array<level, nlevels> levels;

int main() {
    levels l = 
    {
        level{
            row{ 0, 1, 1, 0, 1, 1, 1, 0},
            row{ 0, 1, 1, 0, 1, 1, 1, 0},
            row{ 0, 1, 1, 0, 1, 1, 1, 0},
            row{ 0, 1, 1, 0, 1, 1, 1, 0},
            row{ 0, 0, 0, 0, 0, 0, 0, 0}
        },
        level{
            row{ 0, 1, 1, 0, 1, 1, 1, 0},
            row{ 0, 1, 1, 0, 1, 1, 1, 0},
            row{ 0, 1, 1, 0, 1, 1, 1, 0},
            row{ 0, 1, 1, 0, 1, 1, 1, 0},
            row{ 0, 0, 0, 0, 0, 0, 0, 0}
        },
    };
    for (int i = 0; i < l.size(); i++) {
        std::cout << "level " << i << ":\n" ;
        for (row & r : l[i]) {
            for (cell & c : r)
                std::cout << c << " ";
            std::cout << "\n";
        }
        std::cout << "\n";
    }
}

Note that the examples make some use of C++11 features (initializer lists, range-based for, std::array) that may not be supported by every compiler. While you can work around the initializer lists to initialize the containers and the range-based for loop for printing, there's no std::array prior to C++11.

For reference:

edited May 23, 2017 at 10:26

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answered Feb 2, 2015 at 8:05

moooeeeep

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8 Comments

user63898 Over a year ago

im getting initialization with '{...}' is not allowed for object of type "levels" on the vector example using visual studio 2012

user63898 Over a year ago

also give me banch of error with the std::array example like: 'level' : illegal use of this type as an expression

moooeeeep Over a year ago

@user63898 std::array became part of C++ with the C++11 standard. You might need to check whether your compiler supports that feature or how you can enable it. (Same goes for the range-based-for loop I've used in the example.) I tested both examples with g++ 4.8.3.

user63898 Over a year ago

oo . so its not good i need something that support old compilers ( 2008 ) also

moooeeeep Over a year ago

@user63898 You need to learn about the options you have to initialize a std::vector without using initializer lists: stackoverflow.com/q/2236197/1025391

|

Erbureth · Accepted Answer · 2015-02-02 14:15:29Z

1

You can use more explicit declaration of the LevelsArray type

int LevelsArray[LEVELS_COUNT][MAX_ROW][MAX_CELL] = { {...}, {...} };

However the C++ way would be to use std::vector or std::array (requires C++11):

std::vector<std::vector<std::vector<int>>> LevelsArray =
{
    {
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 0, 0, 0, 0, 0, 0, 0}
    },
    {
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 0, 0, 0, 0, 0, 0, 0}
    }
};

or

std::array<std::array<std::array<int, MAX_CELL>, MAX_ROW>, LEVELS_COUNT> LevelsArray =
{
    {
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 0, 0, 0, 0, 0, 0, 0}
    },
    {
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 0, 0, 0, 0, 0, 0, 0}
    }
};

edited Feb 2, 2015 at 14:15

answered Feb 2, 2015 at 7:48

Erbureth

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4 Comments

legends2k Over a year ago

int LevelsArray[LEVELS_COUNT][MAX_ROW][MAX_CELL] = { anArray1, anArray2}; wouldn't work, you've to give the array elements inside this array.

user63898 Over a year ago

the std::array example gives me :error C2078: too many initializers error

user63898 Over a year ago

vector example gives error: error C2552: 'LevelsArray' : non-aggregates cannot be initialized with initializer list in visual studio 2012

Erbureth Over a year ago

@user63898 You need proper C++11 support for initializer list and std:array, using C++03 would be more complicated.

legends2k · Accepted Answer · 2015-02-02 07:43:38Z

0

You're missing specifying the other dimensions of the container which depends on the element contained. Try this

int LevelsArray[][MAX_ROW][MAX_CELL] =
{
    {
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 0, 0, 0, 0, 0, 0, 0}
    },
    {
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 1, 1, 0, 1, 1, 1, 0},
        { 0, 0, 0, 0, 0, 0, 0, 0}
    }
};

Having the elements (2D arrays) as separate arrays would mean that you cannot store those arrays inside another array; you may only store pointers to them. With this approach, you can refer the inner elements too convienetly with a reference like this

auto const &anArray1 = LevelsArray[0];

and use it elsewhere.

answered Feb 2, 2015 at 7:43

legends2k

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4 Comments

user63898 Over a year ago

is there any way to copy the array to int array not using c++11 and not looping all the Level array ?

legends2k Over a year ago

C++ as a language doesn't support initializing arrays with arrays. You've to copy them manually or use std::copy which too would do the same behind the scenes. If you really want flexible container like you ask, perhaps try std::vector.

user63898 Over a year ago

the vector make me problems also , see above commnets

legends2k Over a year ago

For that you need C++11 where vector gets a std::initializer_list taking constructor. I don't think VS 2012 has it.

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