I want to make a 2d, 3 by 3 ,array like this:

double *array;

void setArray(double x, double y, double z){
    array = {{x,0,0},
             {0,y,0},
             {0,0,z}};
}

I read some posts suggested something like this:

double **array = new double*[3];

void setArray(double x, double y, double z){
   array[0] = new double*[3];
   array[0][0] = x;
   array[0][1] = 0;
   array[0][2] = 0;
   ...

if there any method I can set a 2d array directly using values {{x,0,0},{0,y,0},{0,0,z}}?

Thanks in advance.

• c++
• arrays
• pointers
• 2d

If you want to use lists like {{x,0,0},{0,y,0},{0,0,z}}, you should use arrays with hard-coded size:

double *array; // no good
double array[3][3]; // OK

Fill them with copying:

void setArray(double x, double y, double z){
    double temp[3][3] = {{x,0,0},
                         {0,y,0},
                         {0,0,z}};
    memcpy(&array, &temp, sizeof(array));
}

If you don't need jagged array, and the size is known at design time you can use this syntax to declare it:

double array[3][3];

However, if you want to use an initialisation list, you could do it like this:

typedef double Array[3][3];

Array& array(double x = 0.0, double y = 0.0, double z = 0.0) {
  static double array_[3][3] = {{x,0,0},{0,y,0},{0,0,z}};
  return array_;
}

// init:
array(4,5,8);
// access:
array()[0,2];