1 | 4. n:  5. f: n Alph 6. Bij( n; Alph; f) 7. n1:  8. f1: n1 S.car 9. Bij( n1; S.car; f1) 10. LL:(S.car S.car*)*.
BL:S.car*. t:S.car. mem_f(S.car;t;BL)  ( i: ||LL||. 1of(LL[i]) = t & mem_f(S.car;s;2of(LL[i]))) BL:S.car*. t:S.car. mem_f(S.car;t;BL)  ( a:Alph. S.act(a,t) = s) |