passing array or arrays.

[xontrn]

I get the error:

"error C2664: 'C<T>::C(T **,int,int)' : cannot convert parameter 1
from 'float [2][3]' to 'float **'"

An array of array does not get resolved to a pointer-to-pointer?

#include <iostream>
using namespace std;

template<typename T>
class C
{
public:
C(T** d, int m, int n)
{
mData = new T*[m];
for(int i = 0; i < m; ++i)
mData[i] = new T[n];

for(int i = 0; i < r; ++i)
for(int j = 0; j < c; ++j)
mData[i][j] = d[i][j];

r = m;
c = n;
}

~C()
{
for(int i = 0; i < r; ++i)
delete[] mData[i];

delete[] mData;
}

T& operator()(int i, int j)
{
return mData[i][j];
}

void print()
{
for(int i = 0; i < r; ++i)
{
for(int j = 0; j < c; ++j)
{
cout << data[i][j] << "\t";
}
cout << endl;
}
}

private:
T** data;
int r;
int c;
};

int main()
{
float m[2][3];
m[0][0] = 1.0f;
m[0][1] = 2.0f;
m[0][2] = 3.0f;
m[1][0] = 4.0f;
m[1][1] = 5.0f;
m[1][2] = 6.0f;
m[2][0] = 7.0f;
m[2][1] = 8.0f;
m[2][2] = 9.0f;

C<floatT(m, 2, 3);

T.print();
}

[James Kanze]

On Jul 25, 1:35 am, [e-mail] wrote:

I get the error:

"error C2664: 'C<T>::C(T **,int,int)' : cannot convert parameter 1
from 'float [2][3]' to 'float **'"

An array of array does not get resolved to a pointer-to-pointer?

No. Why should it? An array is converted implicitly to a
pointer, but the result of that conversion is a pointer, not an
array, so no further conversions of the sort apply.

Think about how pointers work, and what the layout of the
various types is in memory, and you'll quickly see why it
couldn't be otherwise. In particular, think about the
implications on pointer arithmetic (which also should explain
why in a pointer to an array, the dimension of the array must be
known).

--
James Kanze (GABI Software) email:ja*********@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientierter Datenverarbeitung
9 place Sémard, 78210 St.-Cyr-l'École, France, [phone]