Getting the contents from cells in a cell array using MEX

I have a 5x1 cell array (each cell has a single number) and I want to pass this cell array as a parameter to a mex function (written in C) and view the contents of the cells. I have written the following mex function.

#include <math.h>
#include <matrix.h>
#include <mex.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

void mexFunction(int nlhs, mxArray *plhs[],
         int nrhs, const mxArray *prhs[])
{

const mwSize *dims; 
const mxArray *cell;
const mxArray *cellArray;
mwIndex jcell;
double *output;

cell = prhs[0];
output = mxGetPr(cell);

dims = mxGetDimensions(prhs[0]);

for (jcell=0; jcell<dims[0]; jcell++) {

    cellArray = mxGetCell(cell,jcell);
    printf("The content at %d is %d\n",jcell,cellArray);

}

return;

}

Lets call the C code above test.c test.c compiles without problems. When I call test(mycell), where mycell is:

mycell = cell(5,1);
mycell{1,1} = 1;
mycell{2,1} = 2;
mycell{3,1} = 3;
mycell{4,1} = 4;
mycell{5,1} = 5;

the mex function prints the following:

The content at 0 is 152353696
The content at 1 is 152353248
The content at 2 is 152354704
The content at 3 is 152353920
The content at 4 is 152352800

What I want is 1, 2, 3, 4, 5 instead of those rubbish numbers. Can anyone please help me solving the problem here, because I can´t see it. I have searched this forum and various sources without success.

Answer 1

[Jan]

mxGetCell replies the pointer to the mxArray element. You currently display the address in the memory, while you want to show the contents:

double  *p;
mxArray *cellElement;  // Typo: * was missing, thanks James
...
for (jcell=0; jcell<dims[0]; jcell++) {
  cellElement = mxGetCell(cell,jcell);
  p = mxGetPr(cellElement)
  mexPrintf("The content at %d is %g\n", jcell, *p);

Notice that this will fail, if the contents is not a double array or if it is empty. a = cell(1,1) create an unpopulated cell, such that mxGetCell replies a NULL pointer and a direct access can crash Matlab.

[gwar]

Thanks, this works. although I had to write (int)*p in the mexPrintf function to get 1,2,3,4,5 and not 0,0,0,0,0.

[Jan]

Then you did not use my suggested %g but %d.

[James Tursa]

Typo:

mxArray *cellEllement; // missing the * above