intuition.
unfold randomFunc, randomFunc_mem.
rewrite H.
case_eq (arrayLookup eqdd x2 a ); intuition.
eapply comp_spec_ret; intuition.
simpl.
case_eq (eqb x a); intuition.
rewrite eqb_leibniz in H1.
subst.
intuition.
comp_skip.
eapply comp_base_exists; intuition.
eapply comp_base_exists; intuition.
eapply comp_spec_ret; intuition.
simpl.
rewrite H.
trivial.
Qed.
Definition G2_1 :=
k_in <-$ {0, 1}^k;
[b, _] <-$2 A _ _ (fun s d => randomFunc_mem _ _ ({0, 1}^c) s (F k_in d)) nil;
ret b.

Theorem G2_1_equiv :
Pr[G1] == Pr[G2_1].