Re: need help in dynamic memory alloction of multi-dimensional array

=?ISO-8859-15?Q?Stefan_N=E4we?= <>
Wed, 10 May 2006 09:48:47 +0200
Alex Blekhman schrieb:

Allen Maki wrote:

When I used the 2 following lines in a simple code, the
code will compile with no error:

long (*pprime)[max2];

pprime = new long[max][max2];

But if I separate the two lines by putting the first in a
and the second line in the constructor of the same class
I will have the under mentioned error messages.

Can you tell me what is wrong?

Stop reinventing the wheel. Use std::vector:

typedef std::vector< long > vector1d;
typedef std::vector< vector1d > vector2d;

const size_t rows = 3;
const size_t cols = 4;

vector2d v2d;


// initialize 2d array with zeros
for(vector2d::iterator it = v2d.begin();
    it != v2d.end();

// now you can access some element
v2d[0][0] = 42;

If you want to avoid `for' statement and make code more
laconic, then there are handy STL functors. Here the 2d
array is initialized in one statement:

// initialize 2d array with zeros
std::for_each(v2d.begin(), v2d.end(),
        std::mem_fun_ref(&vector1d::resize), cols));

What's wrong with this :

  vector2d v2d(rows, vector1d(cols));

That's _one_ (readable) line.

Stefan Naewe

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