How to initialize array of two dimensional arrays in C++ (defined like in code below)?
#include <iostream>
#include <array>
typedef int arr3by6Int[3][6];
typedef arr3by6Int arr3xarr3by6Int[3];
void print3by6(arr3by6Int arr)
{
for(int i = 0; i < 3; i++)
{
for(int j = 0; j < 6; j++)
{
std::cout << arr[i][j] << " ";
}
std::cout << std::endl;
}
}
int main(int argc, char const *argv[])
{
arr3by6Int a = {
{1,2,3,4,5,6},
{0,0,0,0,0,0},
{2,2,2,2,2,2}
};
arr3by6Int b = {
{2,2,3,4,5,6},
{0,0,0,0,0,0},
{2,2,2,2,2,2}
};
arr3by6Int c = {
{3,2,3,4,5,6},
{0,0,0,0,0,0},
{2,2,2,2,2,2}
};
arr3xarr3by6Int d = { a, b, c };
for(int i = 0; i < 3; i++)
{
print3by6(d[i]);
}
return 0;
}
I get these errors:
$ g++ -std=c++11 arrays.cpp -o arrays
arrays.cpp: In function ‘int main(int, const char**)’:
arrays.cpp:39:32: error: array must be initialized with a brace-enclosed initializer
arrays.cpp:39:32: error: array must be initialized with a brace-enclosed initializer
arrays.cpp:39:32: error: array must be initialized with a brace-enclosed initializer
You have #include <array> in your code, so you should use it. Change your types to use std::array<>:
typedef std::array<std::array<int, 6>, 3> arr3by6Int;
typedef std::array<arr3by6Int, 3> arr3xarr3by6Int;
Then, update your initialization lists to match:
arr3by6Int a = {
std::array<int, 6>{1,2,3,4,5,6},
std::array<int, 6>{0,0,0,0,0,0},
std::array<int, 6>{2,2,2,2,2,2}
};
arr3by6Int b = {
std::array<int, 6>{2,2,3,4,5,6},
std::array<int, 6>{0,0,0,0,0,0},
std::array<int, 6>{2,2,2,2,2,2}
};
arr3by6Int c = {
std::array<int, 6>{3,2,3,4,5,6},
std::array<int, 6>{0,0,0,0,0,0},
std::array<int, 6>{2,2,2,2,2,2}
};
In most cases, an object of "C style" array type will degrade to the pointer to the array's first element when used in an expression. Your way of initializing d is attempting to initialize the 3 matrices with pointer values, which won't work.
A std::array is a class, so it won't degrade in that way.
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