(** Normalisation of formulae **)

Inductive Op2 : Set := (* binary relations *)
| OpEq
| OpNEq
| OpLe
| OpGe
| OpLt
| OpGt.(** Normalisation of formulae **)

Inductive Op2 : Set := (* binary relations *)
| OpEq
| OpNEq
| OpLe
| OpGe
| OpLt
| OpGt.(** Normalisation of formulae **)

Inductive Op2 : Set := (* binary relations *)
| OpEq
| OpNEq
| OpLe
| OpGe
| OpLt
| OpGt.(** Normalisation of formulae **)

Inductive Op2 : Set := (* binary relations *)
| OpEq
| OpNEq
| OpLe
| OpGe
| OpLt
| OpGt.(** Normalisation of formulae **)

Inductive Op2 : Set := (* binary relations *)
| OpEq
| OpNEq
| OpLe
| OpGe
| OpLt
| OpGt.(** Normalisation of formulae **)

Inductive Op2 : Set := (* binary relations *)
| OpEq
| OpNEq
| OpLe
| OpGe
| OpLt
| OpGt.(** Normalisation of formulae **)

Inductive Op2 : Set := (* binary relations *)
| OpEq
| OpNEq
| OpLe
| OpGe
| OpLt
| OpGt.Definition eval_op2 (o : Op2) : R -> R -> Prop :=
match o with
| OpEq => req
| OpNEq => fun x y : R => x ~= y
| OpLe => rle
| OpGe => fun x y : R => y <= x
| OpLt => fun x y : R => x < y
| OpGt => fun x y : R => y < x
end.Definition  eval_pexpr : PolEnv -> PExpr C -> R :=
 PEeval rplus rtimes rminus ropp phi pow_phi rpow.#[universes(template)]
Record Formula (T:Type) : Type := Build_Formula{
  Flhs : PExpr T;
  Fop : Op2;
  Frhs : PExpr T
}.#[universes(template)]
Record Formula (T:Type) : Type := Build_Formula{
  Flhs : PExpr T;
  Fop : Op2;
  Frhs : PExpr T
}.#[universes(template)]
Record Formula (T:Type) : Type := Build_Formula{
  Flhs : PExpr T;
  Fop : Op2;
  Frhs : PExpr T
}.#[universes(template)]
Record Formula (T:Type) : Type := Build_Formula{
  Flhs : PExpr T;
  Fop : Op2;
  Frhs : PExpr T
}.#[universes(template)]
Record Formula (T:Type) : Type := Build_Formula{
  Flhs : PExpr T;
  Fop : Op2;
  Frhs : PExpr T
}.Definition eval_formula (env : PolEnv) (f : Formula C) : Prop :=
  let (lhs, op, rhs) := f in
    (eval_op2 op) (eval_pexpr env lhs) (eval_pexpr env rhs).(* We normalize Formulas by moving terms to one side *)

Definition norm := norm_aux cO cI cplus ctimes cminus copp ceqb.Definition psub := Psub cO  cplus cminus copp ceqb.Definition padd  := Padd cO  cplus ceqb.Definition pmul := Pmul cO cI cplus ctimes ceqb.Definition popp := Popp copp.Definition normalise (f : Formula C) : NFormula :=
let (lhs, op, rhs) := f in
  let lhs := norm lhs in
    let rhs := norm rhs in
  match op with
  | OpEq =>  (psub  lhs rhs, Equal)
  | OpNEq => (psub lhs rhs, NonEqual)
  | OpLe =>  (psub rhs lhs, NonStrict)
  | OpGe =>  (psub lhs rhs, NonStrict)
  | OpGt => (psub  lhs rhs, Strict)
  | OpLt => (psub  rhs lhs, Strict)
  end.Definition negate (f : Formula C) : NFormula :=
let (lhs, op, rhs) := f in
  let lhs := norm lhs in
    let rhs := norm rhs in
      match op with
        | OpEq => (psub rhs lhs, NonEqual)
        | OpNEq => (psub rhs lhs, Equal)
        | OpLe => (psub lhs rhs, Strict) (* e <= e' == ~ e > e' *)
        | OpGe => (psub rhs lhs, Strict)
        | OpGt => (psub rhs lhs, NonStrict)
        | OpLt => (psub lhs rhs, NonStrict)
      end.

Theorem negate_correct : forall (env : PolEnv) (f : Formula C), eval_formula env f <-> ~ (eval_nformula env (negate f)).