Passing custom size multidimensional array to function

Question

I have array with known x size (5) and the y is taken from variable, so the array is something like this - array[5][y];

And now I'm quite troubled how to pass it to function, I won't edit it, just read the data from it.

I thought to do something like this:

void someFunction(double **array)

but I get

convert error: cannot convert `double (*)[((unsigned int)((int)n))]' to `double**' for argument `2' to `void findMax(int, double**, int)'|

Please post the code you are having trouble with. Post the function definition and your calling code. — pstrjds
– pstrjds, Commented Mar 18, 2013 at 13:18

sh03 · Accepted Answer · 2013-03-18 13:30:14Z

1

For Array [5][x]

Unfortunately you cannot define a type for an array like double[5][]. You can only omit the first dimension of a multidimensional array, not the last.

For Array [x][5]

You should go with void someFunction(double array[][5], int size). And then you loop trough the elements with for (int i = 0; i < size; i++).

Example:

void someFunction(double array[][5], int size) {
    for (int k = 0; i < size; i++)
        for (int i = 0; i < 5; i++)
            std::cout << array[k][i] << std::endl;
}


double a[10][5];
// populate data
someFunction(a, 10);

Usually it's preferred to use std:: containers instead of raw C arrays.

Take a look at std::vector for example.

edited Mar 18, 2013 at 13:30

answered Mar 18, 2013 at 13:18

sh03

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4 Comments

Edgaras Ausvicas Over a year ago

I know about vectors, but the thing is that teachers wants me to do some excercises with arrays, because according to her std is for "lazy people" ^^

sh03 Over a year ago

@EdgarasAusvicas, I've been there aswell. I know what you are talking about.

Edgaras Ausvicas Over a year ago

by the way now im getting this: declaration of `array' as multidimensional array must have bounds for all dimensions except the first

juanchopanza Over a year ago

@EdgarasAusvicas your teacher should not be allowed to teach C++.

Irisciences · Accepted Answer · 2013-03-18 14:42:41Z

0

If you are not using the STL, you can also do this:

void someFunction(double **mat, const int Xsize, const int Ysize )
{
    for(unsigned int i = 0 ; i < Xsize ; ++i)
    {
        for(unsigned int j = 0 ; j < Ysize ; ++j)
        {
            std::cout << ((double *)mat + Ysize * i)[j] << "  " ;
        }
        std::cout << std::endl;
    }

    return ;
}

And call the function like this:

int main(int argc, char** argv)
{
    double matrice[2][3] = {{1,2,3},{4,5,6}};
    someFunction( (double**)matrice, 2, 3 );
    return 1;
}

answered Mar 18, 2013 at 14:42

Irisciences

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