struct nicestream
{ string wholeline;
  int numtaken;
  int length; };

char getchar(nicestream & ns)
{ if (ns.numtaken < ns.length)
  { char c = ns.wholeline[ns.numtaken];
    ns.numtaken += 1;
    return c; }
  else
    return '\n'; }

void backchar(
   WHAT GOES HERE?

WHERE DO WE GO NEXT?