void writeTENSOR2file(TENSOR2 x,char *fname,char *varname,char *mode)
{
  /* MODES:
     "r":  Open file for reading only; determines the current version of the MAT-file by inspecting the files and preserves the current version.
     "u":  Open file for update, both reading and writing, but does not create the file if the file does not exist (equivalent to the r+ mode of fopen); determines the current version of the MAT-file by inspecting the files and preserves the current version.
     "w":  Open file for writing only; deletes previous contents, if any.
  */
 
  mxArray *A;
  MATFile *fid;
  allocArrnCopy2(&A,x,1);
  fid = matOpen(fname,mode);
  matPutVariable(fid,varname,A);
  matClose(fid);
  mxDestroyArray(A);
}


void writeTENSOR3file(TENSOR3 x,char *fname,char *varname,char *mode)
{
  mxArray *A;
  MATFile *fid;
  allocArrnCopy3(&A,x,1);
  fid = matOpen(fname,mode);
  matPutVariable(fid,varname,A);
  matClose(fid);
  mxDestroyArray(A);
}

void writeTENSOR4file(TENSOR4 x,char *fname,char *varname,char *mode)
{
  mxArray *A;
  MATFile *fid;
  allocArrnCopy4(&A,x,1);
  fid = matOpen(fname,mode);
  matPutVariable(fid,varname,A);
  matClose(fid);
  mxDestroyArray(A);
}