function err=errcheck(n, out, iter);
%checks error in n
%err=1 if there is error
%err=0 otherwise
%prints message in the file out if there is an error
%out must be opened and closed in the calling program

err=0;
if (length(n) == 0);
   if (iter==0);
      fprintf(out,'error in simulation input file, line 1.\n');
   else;
      fprintf(out,'error in simulation input file ');
      fprintf(out,'at, before or after iteration record %d', iter);
   end;
   fprintf(out,'program stops');
   quit;
   err=1;
end;