persistent(g)?
g<<-get_choice?
.
A=get_choice-g, B={a;b}, set_choice(A+g)?
;
B={a;b}, A=get_choice-g, set_choice(A+g)?
;
;
A1=get_choice-g, B={a;b}, A2=get_choice-g, C=exists_choice(A1+g,A2+g)?
;
;
A1=get_choice-g, A2=get_choice-g, C=exists_choice(A1+g,A2+g)?
;
A1=get_choice-g?
B={a;b}?
set_choice(A1+g)?
;
A1=get_choice-g?
B=exists_choice(A1+g,get_choice)?
;
;
A1=get_choice-g?
A2=get_choice-g?
B=exists_choice(A1+g,A2+g)?
;
;
;
