A.2.4 Cell Arrays with Mex-Files

We can perform exactly the same operations in Cell arrays in mex-files as we can in oct-files. An example that reduplicates the functional of the celldemo.cc oct-file in a mex-file is given by mycell.c as below

     #include "mex.h"
     
     void
     mexFunction (int nlhs, mxArray* plhs[], int nrhs, 
                  const mxArray* prhs[])
     {
       mwSize n;
       mwIndex i;
     
       if (nrhs != 1 || ! mxIsCell (prhs[0]))
         mexErrMsgTxt ("expects cell");
     
       n = mxGetNumberOfElements (prhs[0]);
       n = (n > nlhs ? nlhs : n);
       
       for (i = 0; i < n; i++)
         plhs[i] = mxDuplicateArray (mxGetCell (prhs[0], i));
     }

which as can be seen below has exactly the same behavior as the oct-file version.

     [b1, b2, b3] = mycell ({1, [1, 2], "test"})
     ⇒
     b1 =  1
     b2 =
     
        1   2
     
     b3 = test

Note in the example the use of the mxDuplicateArray function. This is needed as the mxArray pointer returned by mxGetCell might be deallocated. The inverse function to mxGetCell is mcSetCell and is defined as

     void mxSetCell (mxArray *ptr, int idx, mxArray *val);

Finally, to create a cell array or matrix, the appropriate functions are

     mxArray *mxCreateCellArray (int ndims, const int *dims);
     mxArray *mxCreateCellMatrix (int m, int n);