array initializer / conversion to pointer

[Alexander Stippler]

Hello,

I've got a quite simple question. I want to have something like

int
main()
{
double array[3][3] = {{1,2,3}, {4,5,6}, {7,8,9}};
double **field;
field = array;
}

The compiler complains an not allowed conversion in the assignment
field = array;
It's neccessary that field is of type double**. How to manage an
initialization like the above?

regards,
alex

[Barry Schwarz]

On Thu, 27 May 2004 14:06:45 +0200, Alexander Stippler
<st**@mathemati k.uni-ulm.de> wrote:

Hello,

I've got a quite simple question. I want to have something like

int
main()
{
double array[3][3] = {{1,2,3}, {4,5,6}, {7,8,9}};
double **field;
field = array;
}

The compiler complains an not allowed conversion in the assignment
field = array;
It's neccessary that field is of type double**. How to manage an
initializati on like the above?

Since you claim you cannot change the type of field, your only other
option is to change the type of array. You can use

double *array[3];
double xarray[3][3] = {{1,2,3}, {4,5,6}, {7,8,9}};
for (i = 0; i < 2; i++)
array[i] = xarray[i];
field = array;

All three variables (array, xarray, and field) can use double
subscript notation (e.g., field[i][j]) to reference individual
doubles.
<<Remove the del for email>>

[Peter Shaggy Haywood]

Groovy hepcat Alexander Stippler was jivin' on Thu, 27 May 2004
15:54:10 +0200 in comp.lang.c.
Re: array initializer / conversion to pointer's a cool scene! Dig it!

Joona I Palaste wrote:

Alexander Stippler <st**@mathemati k.uni-ulm.de> scribbled the following:

int
main()
{
double array[3][3] = {{1,2,3}, {4,5,6}, {7,8,9}};
double **field;
field = array;
}

The compiler complains an not allowed conversion in the assignment
field = array;
It's neccessary that field is of type double**. How to manage an
initialization like the above?

Declare field as double (*field)[3] instead.

Sorry, but I cannot influence the type of field, as I already mentioned in
my first posting! It is 'external' to my influence. I need it to be
double **, so what?

Then try something like this:

int main(void)
{
double array[3][3] = {{1,2,3}, {4,5,6}, {7,8,9}};
double **field;
double *foo[3];
int i;

for(i = 0; i < (sizeof foo / sizeof *foo); i++)
foo[i] = array[i];

field = foo;
}

--

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[E. Robert Tisdale]

Alexander Stippler wrote:

I've got a quite simple question. I want to have something like

int
main(int argc, char* argv[]) {
double array[3][3] = {{1,2,3}, {4,5,6}, {7,8,9}};
double **field = &(array[0][0]);
This is probably what you meant.
return 0;
}

The compiler complains an not allowed conversion in the assignment

field = array;

It's neccessary that field is of type double**.
How to manage an initialization like the above? cat main.c #include <stdio.h>
#include <stdlib.h>

void f(size_t m, size_t n, const double a[m][n]) {
for (size_t i = 0; i < m; ++i) {
for (size_t j = 0; j < n; ++j)
fprintf(stdout, " %f", a[i][j]);
fprintf(stdout, "\n");
}
}

int
main(int argc, char* argv[]) {
const size_t m = 3;
const size_t n = 3;
const double array[][3] = {{1,2,3}, {4,5,6}, {7,8,9}};
fprintf(stdout, "array =\n");
f(m, n, array);
return EXIT_SUCCESS;
}
gcc -Wall -std=c99 -pedantic -o main main.c
./main

array =
1.000000 2.000000 3.000000
4.000000 5.000000 6.000000
7.000000 8.000000 9.000000