fact: Definition getEquiv (Ar : rArray vM) (a : rNat) : list rZ * bool := match rArrayGet vM Ar a with | ref r => match r with | rZPlus r0 => match rArrayGet vM Ar r0 with | ref _ => (nil, true) | class L => (rZPlus r0 :: L, false) end | rZMinus r0 => match rArrayGet vM Ar r0 with | ref _ => (nil, true) | class L => (rZPlus r0 :: L, true) end end | class L => (rZPlus a :: L, false) end.