source: doc/theses/jiada_liang_MMath/test.cfa

enum Alphabet {
        A = 'A', B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z,
        a = 'a', b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z
};


forall( istype & | istream( istype ) | { istype & ?|?( istype &, E & ); } )
istype & ?|?( istype & is, E & e ) {
        choose ( e ) {
          case A: is | label( A ); e = A;
          case B: is | label( B ); e = B;
          case C: is | label( C ); e = C;
        } // choose
        return is;
}

forall( ostype & | ostream( ostype ) | { ostype & ?|?( ostype &, E ); } )
        ostype & ?|?( ostype & os, E e ) {
        choose ( e ) {
          case A: os | label( A );
          case B: os | label( B );
          case C: os | label( C );
        } // choose
        return os;
}

enum( char * ) Friends { Fred = "FRED", Mary = "MARY", Jane = "Jane" };

forall( istype & | istream( istype ) | { istype & ?|?( istype &, Friends & ); } )
istype & ?|?( istype & is, Friends & friend ) {
        choose ( friend ) {
          case Fred: is | label( A ); friend = A;
          case Mary: is | label( B ); friend = B;
          case Jane: is | label( C ); friend = C;
        } // choose
        return is;
}

forall( ostype & | ostream( ostype ) | { ostype & ?|?( ostype &, Friends ); } )
        ostype & ?|?( ostype & os, Friends friend ) {
        choose ( friend ) {
          case Fred: os | value( Fred );
          case Mary: os | value( Mary );
          case Jane: os | value( Jane );
        } // choose
        return os;
}


int main() {
        E e = A;
        sin | e;
        sout | e;
        Friends friend = Mary;
        sin | friend;
        sout | friend;
}