Inductive ZArithProof :=
| DoneProof
| RatProof : ZWitness -> ZArithProof -> ZArithProof
| CutProof : ZWitness -> ZArithProof -> ZArithProof
| SplitProof : PolC Z -> ZArithProof -> ZArithProof -> ZArithProof
| EnumProof : ZWitness -> ZWitness -> list ZArithProof -> ZArithProof
| ExProof   : positive -> ZArithProof -> ZArithProof
(*ExProof x : exists z t, x = z - t /\ z >= 0 /\ t >= 0 *)
.Inductive ZArithProof :=
| DoneProof
| RatProof : ZWitness -> ZArithProof -> ZArithProof
| CutProof : ZWitness -> ZArithProof -> ZArithProof
| SplitProof : PolC Z -> ZArithProof -> ZArithProof -> ZArithProof
| EnumProof : ZWitness -> ZWitness -> list ZArithProof -> ZArithProof
| ExProof   : positive -> ZArithProof -> ZArithProof
(*ExProof x : exists z t, x = z - t /\ z >= 0 /\ t >= 0 *)
.Inductive ZArithProof :=
| DoneProof
| RatProof : ZWitness -> ZArithProof -> ZArithProof
| CutProof : ZWitness -> ZArithProof -> ZArithProof
| SplitProof : PolC Z -> ZArithProof -> ZArithProof -> ZArithProof
| EnumProof : ZWitness -> ZWitness -> list ZArithProof -> ZArithProof
| ExProof   : positive -> ZArithProof -> ZArithProof
(*ExProof x : exists z t, x = z - t /\ z >= 0 /\ t >= 0 *)
.Inductive ZArithProof :=
| DoneProof
| RatProof : ZWitness -> ZArithProof -> ZArithProof
| CutProof : ZWitness -> ZArithProof -> ZArithProof
| SplitProof : PolC Z -> ZArithProof -> ZArithProof -> ZArithProof
| EnumProof : ZWitness -> ZWitness -> list ZArithProof -> ZArithProof
| ExProof   : positive -> ZArithProof -> ZArithProof
(*ExProof x : exists z t, x = z - t /\ z >= 0 /\ t >= 0 *)
.Inductive ZArithProof :=
| DoneProof
| RatProof : ZWitness -> ZArithProof -> ZArithProof
| CutProof : ZWitness -> ZArithProof -> ZArithProof
| SplitProof : PolC Z -> ZArithProof -> ZArithProof -> ZArithProof
| EnumProof : ZWitness -> ZWitness -> list ZArithProof -> ZArithProof
| ExProof   : positive -> ZArithProof -> ZArithProof
(*ExProof x : exists z t, x = z - t /\ z >= 0 /\ t >= 0 *)
.Inductive ZArithProof :=
| DoneProof
| RatProof : ZWitness -> ZArithProof -> ZArithProof
| CutProof : ZWitness -> ZArithProof -> ZArithProof
| SplitProof : PolC Z -> ZArithProof -> ZArithProof -> ZArithProof
| EnumProof : ZWitness -> ZWitness -> list ZArithProof -> ZArithProof
| ExProof   : positive -> ZArithProof -> ZArithProof
(*ExProof x : exists z t, x = z - t /\ z >= 0 /\ t >= 0 *)
.Inductive ZArithProof :=
| DoneProof
| RatProof : ZWitness -> ZArithProof -> ZArithProof
| CutProof : ZWitness -> ZArithProof -> ZArithProof
| SplitProof : PolC Z -> ZArithProof -> ZArithProof -> ZArithProof
| EnumProof : ZWitness -> ZWitness -> list ZArithProof -> ZArithProof
| ExProof   : positive -> ZArithProof -> ZArithProof
(*ExProof x : exists z t, x = z - t /\ z >= 0 /\ t >= 0 *)
.Definition isZ0 (x:Z) :=
  match x with
    | Z0 => true
    | _  => false
  end.

Lemma isZ0_0 : forall x, isZ0 x = true <-> x = 0.