6 bool equal(struct Expr obj1, struct Expr obj2);
8 bool nil_p(struct Expr obj);
9 bool symbol_p(struct Expr obj);
10 bool cons_p(struct Expr obj);
12 /// You should never detroy the result of assoc because it always
13 /// returns the subexpression of alist
14 struct Expr assoc(struct Expr key, struct Expr alist);