The Coq Proof Assistant

# Library Coq.micromega.EnvRing

Set Implicit Arguments.
Require Import Setoid Morphisms Env BinPos BinNat BinInt.
Require Export Ring_theory.
Local Open Scope positive_scope.
Import RingSyntax.
Definition of polynomial expressions
#[universes(template)]
Inductive PExpr {C} : Type :=
| PEc : C -> PExpr
| PEX : positive -> PExpr
| PEadd : PExpr -> PExpr -> PExpr
| PEsub : PExpr -> PExpr -> PExpr
| PEmul : PExpr -> PExpr -> PExpr
| PEopp : PExpr -> PExpr
| PEpow : PExpr -> N -> PExpr.
Arguments PExpr : clear implicits.
Register PEc as micromega.PExpr.PEc.
Register PEX as micromega.PExpr.PEX.
Register PEadd as micromega.PExpr.PEadd.
Register PEsub as micromega.PExpr.PEsub.
Register PEmul as micromega.PExpr.PEmul.
Register PEopp as micromega.PExpr.PEopp.
Register PEpow as micromega.PExpr.PEpow.
#[universes(template)]
Inductive Pol {C} : Type :=
| Pc : C -> Pol
| Pinj : positive -> Pol -> Pol
| PX : Pol -> positive -> Pol -> Pol.
Arguments Pol : clear implicits.
Register Pc as micromega.Pol.Pc.
Register Pinj as micromega.Pol.Pinj.
Register PX as micromega.Pol.PX.
Section MakeRingPol.
Variable R:Type.
Variable (rO rI : R) (radd rmul rsub: R->R->R) (ropp : R->R).
Variable req : R -> R -> Prop.
Variable Rsth : Equivalence req.
Variable Reqe : ring_eq_ext radd rmul ropp req.
Variable ARth : almost_ring_theory rO rI radd rmul rsub ropp req.
Variable C: Type.
Variable (cO cI: C) (cadd cmul csub : C->C->C) (copp : C->C).
Variable ceqb : C->C->bool.
Variable phi : C -> R.
Variable CRmorph : ring_morph rO rI radd rmul rsub ropp req
cO cI cadd cmul csub copp ceqb phi.
Variable Cpow : Type.
Variable Cp_phi : N -> Cpow.
Variable rpow : R -> Cpow -> R.
Variable pow_th : power_theory rI rmul req Cp_phi rpow.
Notation "0" := rO. Notation "1" := rI.
Infix "+" := radd. Infix "*" := rmul.
Infix "-" := rsub. Notation "- x" := (ropp x).
Infix "==" := req.
Infix "^" := (pow_pos rmul).
Infix "+!" := cadd. Infix "*!" := cmul.
Infix "-! " := csub. Notation "-! x" := (copp x).
Infix "?=!" := ceqb. Notation "[ x ]" := (phi x).
Add Morphism radd with signature (req ==> req ==> req) as radd_ext.
Add Morphism rmul with signature (req ==> req ==> req) as rmul_ext.
Add Morphism ropp with signature (req ==> req) as ropp_ext.
Add Morphism rsub with signature (req ==> req ==> req) as rsub_ext.
Ltac rsimpl := gen_srewrite Rsth Reqe ARth.
Ltac add_push := gen_add_push radd Rsth Reqe ARth.
Ltac mul_push := gen_mul_push rmul Rsth Reqe ARth.
Ltac add_permut_rec t :=
match t with
| ?x + ?y => add_permut_rec y || add_permut_rec x
| _ => add_push t; apply (Radd_ext Reqe); [|reflexivity]
end.
Ltac add_permut :=
repeat (reflexivity ||
match goal with |- ?t == _ => add_permut_rec t end).
Ltac mul_permut_rec t :=
match t with
| ?x * ?y => mul_permut_rec y || mul_permut_rec x
| _ => mul_push t; apply (Rmul_ext Reqe); [|reflexivity]
end.
Ltac mul_permut :=
repeat (reflexivity ||
match goal with |- ?t == _ => mul_permut_rec t end).
Notation PExpr := (PExpr C).
Notation Pol := (Pol C).
Implicit Types pe : PExpr.
Implicit Types P : Pol.
Definition P0 := Pc cO.
Definition P1 := Pc cI.
Fixpoint Peq (P P' : Pol) {struct P'} : bool :=
match P, P' with
| Pc c, Pc c' => c ?=! c'
| Pinj j Q, Pinj j' Q' =>
match j ?= j' with
| Eq => Peq Q Q'
| _ => false
end
| PX P i Q, PX P' i' Q' =>
match i ?= i' with
| Eq => if Peq P P' then Peq Q Q' else false
| _ => false
end
| _, _ => false
end.
Infix "?==" := Peq.
Definition mkPinj j P :=
match P with
| Pc _ => P
| Pinj j' Q => Pinj (j + j') Q
| _ => Pinj j P
end.
Definition mkPinj_pred j P :=
match j with
| xH => P
| xO j => Pinj (Pos.pred_double j) P
| xI j => Pinj (xO j) P
end.
Definition mkPX P i Q :=
match P with
| Pc c => if c ?=! cO then mkPinj xH Q else PX P i Q
| Pinj _ _ => PX P i Q
| PX P' i' Q' => if Q' ?== P0 then PX P' (i' + i) Q else PX P i Q
end.
Definition mkXi i := PX P1 i P0.
Definition mkX := mkXi 1.
Opposite of addition
Fixpoint Popp (P:Pol) : Pol :=
match P with
| Pc c => Pc (-! c)
| Pinj j Q => Pinj j (Popp Q)
| PX P i Q => PX (Popp P) i (Popp Q)
end.
Notation "-- P" := (Popp P).
Addition et subtraction
Fixpoint PaddC (P:Pol) (c:C) : Pol :=
match P with
| Pc c1 => Pc (c1 +! c)
| Pinj j Q => Pinj j (PaddC Q c)
| PX P i Q => PX P i (PaddC Q c)
end.
Fixpoint PsubC (P:Pol) (c:C) : Pol :=
match P with
| Pc c1 => Pc (c1 -! c)
| Pinj j Q => Pinj j (PsubC Q c)
| PX P i Q => PX P i (PsubC Q c)
end.
Section PopI.
Variable Pop : Pol -> Pol -> Pol.
Variable Q : Pol.
Fixpoint PaddI (j:positive) (P:Pol) : Pol :=
match P with
| Pc c => mkPinj j (PaddC Q c)
| Pinj j' Q' =>
match Z.pos_sub j' j with
| Zpos k => mkPinj j (Pop (Pinj k Q') Q)
| Z0 => mkPinj j (Pop Q' Q)
| Zneg k => mkPinj j' (PaddI k Q')
end
| PX P i Q' =>
match j with
| xH => PX P i (Pop Q' Q)
| xO j => PX P i (PaddI (Pos.pred_double j) Q')
| xI j => PX P i (PaddI (xO j) Q')
end
end.
Fixpoint PsubI (j:positive) (P:Pol) : Pol :=
match P with
| Pc c => mkPinj j (PaddC (--Q) c)
| Pinj j' Q' =>
match Z.pos_sub j' j with
| Zpos k => mkPinj j (Pop (Pinj k Q') Q)
| Z0 => mkPinj j (Pop Q' Q)
| Zneg k => mkPinj j' (PsubI k Q')
end
| PX P i Q' =>
match j with
| xH => PX P i (Pop Q' Q)
| xO j => PX P i (PsubI (Pos.pred_double j) Q')
| xI j => PX P i (PsubI (xO j) Q')
end
end.
Variable P' : Pol.
Fixpoint PaddX (i':positive) (P:Pol) : Pol :=
match P with
| Pc c => PX P' i' P
| Pinj j Q' =>
match j with
| xH => PX P' i' Q'
| xO j => PX P' i' (Pinj (Pos.pred_double j) Q')
| xI j => PX P' i' (Pinj (xO j) Q')
end
| PX P i Q' =>
match Z.pos_sub i i' with
| Zpos k => mkPX (Pop (PX P k P0) P') i' Q'
| Z0 => mkPX (Pop P P') i Q'
| Zneg k => mkPX (PaddX k P) i Q'
end
end.
Fixpoint PsubX (i':positive) (P:Pol) : Pol :=
match P with
| Pc c => PX (--P') i' P
| Pinj j Q' =>
match j with
| xH => PX (--P') i' Q'
| xO j => PX (--P') i' (Pinj (Pos.pred_double j) Q')
| xI j => PX (--P') i' (Pinj (xO j) Q')
end
| PX P i Q' =>
match Z.pos_sub i i' with
| Zpos k => mkPX (Pop (PX P k P0) P') i' Q'
| Z0 => mkPX (Pop P P') i Q'
| Zneg k => mkPX (PsubX k P) i Q'
end
end.
End PopI.
Fixpoint Padd (P P': Pol) {struct P'} : Pol :=
match P' with
| Pc c' => PaddC P c'
| Pinj j' Q' => PaddI Padd Q' j' P
| PX P' i' Q' =>
match P with
| Pc c => PX P' i' (PaddC Q' c)
| Pinj j Q =>
match j with
| xH => PX P' i' (Padd Q Q')
| xO j => PX P' i' (Padd (Pinj (Pos.pred_double j) Q) Q')
| xI j => PX P' i' (Padd (Pinj (xO j) Q) Q')
end
| PX P i Q =>
match Z.pos_sub i i' with
| Zpos k => mkPX (Padd (PX P k P0) P') i' (Padd Q Q')
| Z0 => mkPX (Padd P P') i (Padd Q Q')
| Zneg k => mkPX (PaddX Padd P' k P) i (Padd Q Q')
end
end
end.
Infix "++" := Padd.
Fixpoint Psub (P P': Pol) {struct P'} : Pol :=
match P' with
| Pc c' => PsubC P c'
| Pinj j' Q' => PsubI Psub Q' j' P
| PX P' i' Q' =>
match P with
| Pc c => PX (--P') i' (PaddC (--Q') c)
| Pinj j Q =>
match j with
| xH => PX (--P') i' (Psub Q Q')
| xO j => PX (--P') i' (Psub (Pinj (Pos.pred_double j) Q) Q')
| xI j => PX (--P') i' (Psub (Pinj (xO j) Q) Q')
end
| PX P i Q =>
match Z.pos_sub i i' with
| Zpos k => mkPX (Psub (PX P k P0) P') i' (Psub Q Q')
| Z0 => mkPX (Psub P P') i (Psub Q Q')
| Zneg k => mkPX (PsubX Psub P' k P) i (Psub Q Q')
end
end
end.
Infix "--" := Psub.
Multiplication
Fixpoint PmulC_aux (P:Pol) (c:C) : Pol :=
match P with
| Pc c' => Pc (c' *! c)
| Pinj j Q => mkPinj j (PmulC_aux Q c)
| PX P i Q => mkPX (PmulC_aux P c) i (PmulC_aux Q c)
end.
Definition PmulC P c :=
if c ?=! cO then P0 else
if c ?=! cI then P else PmulC_aux P c.
Section PmulI.
Variable Pmul : Pol -> Pol -> Pol.
Variable Q : Pol.
Fixpoint PmulI (j:positive) (P:Pol) : Pol :=
match P with
| Pc c => mkPinj j (PmulC Q c)
| Pinj j' Q' =>
match Z.pos_sub j' j with
| Zpos k => mkPinj j (Pmul (Pinj k Q') Q)
| Z0 => mkPinj j (Pmul Q' Q)
| Zneg k => mkPinj j' (PmulI k Q')
end
| PX P' i' Q' =>
match j with
| xH => mkPX (PmulI xH P') i' (Pmul Q' Q)
| xO j' => mkPX (PmulI j P') i' (PmulI (Pos.pred_double j') Q')
| xI j' => mkPX (PmulI j P') i' (PmulI (xO j') Q')
end
end.
End PmulI.
Fixpoint Pmul (P P'' : Pol) {struct P''} : Pol :=
match P'' with
| Pc c => PmulC P c
| Pinj j' Q' => PmulI Pmul Q' j' P
| PX P' i' Q' =>
match P with
| Pc c => PmulC P'' c
| Pinj j Q =>
let QQ' :=
match j with
| xH => Pmul Q Q'
| xO j => Pmul (Pinj (Pos.pred_double j) Q) Q'
| xI j => Pmul (Pinj (xO j) Q) Q'
end in
mkPX (Pmul P P') i' QQ'
| PX P i Q=>
let QQ' := Pmul Q Q' in
let PQ' := PmulI Pmul Q' xH P in
let QP' := Pmul (mkPinj xH Q) P' in
let PP' := Pmul P P' in
(mkPX (mkPX PP' i P0 ++ QP') i' P0) ++ mkPX PQ' i QQ'
end
end.
Infix "**" := Pmul.
Fixpoint Psquare (P:Pol) : Pol :=
match P with
| Pc c => Pc (c *! c)
| Pinj j Q => Pinj j (Psquare Q)
| PX P i Q =>
let twoPQ := Pmul P (mkPinj xH (PmulC Q (cI +! cI))) in
let Q2 := Psquare Q in
let P2 := Psquare P in
mkPX (mkPX P2 i P0 ++ twoPQ) i Q2
end.
Monomial
A monomial is X1^k1...Xi^ki. Its representation is a simplified version of the polynomial representation:

- mon0 correspond to the polynom P1.
- (zmon j M) corresponds to (Pinj j ...), i.e. skip j variable indices.
- (vmon i M) is X^i*M with X the current variable, its corresponds to (PX P1 i ...)]

Inductive Mon: Set :=
| mon0: Mon
| zmon: positive -> Mon -> Mon
| vmon: positive -> Mon -> Mon.
Definition mkZmon j M :=
match M with mon0 => mon0 | _ => zmon j M end.
Definition zmon_pred j M :=
match j with xH => M | _ => mkZmon (Pos.pred j) M end.
Definition mkVmon i M :=
match M with
| mon0 => vmon i mon0
| zmon j m => vmon i (zmon_pred j m)
| vmon i' m => vmon (i+i') m
end.
Fixpoint MFactor (P: Pol) (M: Mon) : Pol * Pol :=
match P, M with
_, mon0 => (Pc cO, P)
| Pc _, _ => (P, Pc cO)
| Pinj j1 P1, zmon j2 M1 =>
match (j1 ?= j2) with
Eq => let (R,S) := MFactor P1 M1 in
(mkPinj j1 R, mkPinj j1 S)
| Lt => let (R,S) := MFactor P1 (zmon (j2 - j1) M1) in
(mkPinj j1 R, mkPinj j1 S)
| Gt => (P, Pc cO)
end
| Pinj _ _, vmon _ _ => (P, Pc cO)
| PX P1 i Q1, zmon j M1 =>
let M2 := zmon_pred j M1 in
let (R1, S1) := MFactor P1 M in
let (R2, S2) := MFactor Q1 M2 in
(mkPX R1 i R2, mkPX S1 i S2)
| PX P1 i Q1, vmon j M1 =>
match (i ?= j) with
Eq => let (R1,S1) := MFactor P1 (mkZmon xH M1) in
(mkPX R1 i Q1, S1)
| Lt => let (R1,S1) := MFactor P1 (vmon (j - i) M1) in
(mkPX R1 i Q1, S1)
| Gt => let (R1,S1) := MFactor P1 (mkZmon xH M1) in
(mkPX R1 i Q1, mkPX S1 (i-j) (Pc cO))
end
end.
Definition POneSubst (P1: Pol) (M1: Mon) (P2: Pol): option Pol :=
let (Q1,R1) := MFactor P1 M1 in
match R1 with
(Pc c) => if c ?=! cO then None
else Some (Padd Q1 (Pmul P2 R1))
| _ => Some (Padd Q1 (Pmul P2 R1))
end.
Fixpoint PNSubst1 (P1: Pol) (M1: Mon) (P2: Pol) (n: nat) : Pol :=
match POneSubst P1 M1 P2 with
Some P3 => match n with S n1 => PNSubst1 P3 M1 P2 n1 | _ => P3 end
| _ => P1
end.
Definition PNSubst (P1: Pol) (M1: Mon) (P2: Pol) (n: nat): option Pol :=
match POneSubst P1 M1 P2 with
Some P3 => match n with S n1 => Some (PNSubst1 P3 M1 P2 n1) | _ => None end
| _ => None
end.
Fixpoint PSubstL1 (P1: Pol) (LM1: list (Mon * Pol)) (n: nat) : Pol :=
match LM1 with
cons (M1,P2) LM2 => PSubstL1 (PNSubst1 P1 M1 P2 n) LM2 n
| _ => P1
end.
Fixpoint PSubstL (P1: Pol) (LM1: list (Mon * Pol)) (n: nat) : option Pol :=
match LM1 with
cons (M1,P2) LM2 =>
match PNSubst P1 M1 P2 n with
Some P3 => Some (PSubstL1 P3 LM2 n)
| None => PSubstL P1 LM2 n
end
| _ => None
end.
Fixpoint PNSubstL (P1: Pol) (LM1: list (Mon * Pol)) (m n: nat) : Pol :=
match PSubstL P1 LM1 n with
Some P3 => match m with S m1 => PNSubstL P3 LM1 m1 n | _ => P3 end
| _ => P1
end.
Evaluation of a polynomial towards R
Fixpoint Pphi(l:Env R) (P:Pol) : R :=
match P with
| Pc c => [c]
| Pinj j Q => Pphi (jump j l) Q
| PX P i Q => Pphi l P * (hd l) ^ i + Pphi (tail l) Q
end.
Reserved Notation "P @ l " (at level 10, no associativity).
Notation "P @ l " := (Pphi l P).
Evaluation of a monomial towards R
Fixpoint Mphi(l:Env R) (M: Mon) : R :=
match M with
| mon0 => rI
| zmon j M1 => Mphi (jump j l) M1
| vmon i M1 => Mphi (tail l) M1 * (hd l) ^ i
end.
Notation "M @@ l" := (Mphi l M) (at level 10, no associativity).
Proofs
Ltac destr_pos_sub :=
match goal with |- context [Z.pos_sub ?x ?y] =>
generalize (Z.pos_sub_discr x y); destruct (Z.pos_sub x y)
end.
Lemma Peq_ok P P' : (P ?== P') = true -> forall l, P@l == P'@ l.
Lemma Peq_spec P P' :
BoolSpec (forall l, P@l == P'@l) True (P ?== P').
Lemma Pphi0 l : P0@l == 0.
Lemma Pphi1 l : P1@l == 1.
Lemma env_morph p e1 e2 :
(forall x, e1 x = e2 x) -> p @ e1 = p @ e2.
Lemma Pjump_add P i j l :
P @ (jump (i + j) l) = P @ (jump j (jump i l)).
Lemma Pjump_xO_tail P p l :
P @ (jump (xO p) (tail l)) = P @ (jump (xI p) l).
Lemma Pjump_pred_double P p l :
P @ (jump (Pos.pred_double p) (tail l)) = P @ (jump (xO p) l).
Lemma mkPinj_ok j l P : (mkPinj j P)@l == P@(jump j l).
Lemma pow_pos_add x i j : x^(j + i) == x^i * x^j.
Lemma ceqb_spec c c' : BoolSpec ([c] == [c']) True (c ?=! c').
Lemma mkPX_ok l P i Q :
(mkPX P i Q)@l == P@l * (hd l)^i + Q@(tail l).
Hint Rewrite
Pphi0
Pphi1
mkPinj_ok
mkPX_ok
(morph0 CRmorph)
(morph1 CRmorph)
(morph0 CRmorph)
(morph_add CRmorph)
(morph_mul CRmorph)
(morph_sub CRmorph)
(morph_opp CRmorph)
: Esimpl.
Ltac Esimpl := try rewrite_db Esimpl; rsimpl; simpl.
Lemma PaddC_ok c P l : (PaddC P c)@l == P@l + [c].
Lemma PsubC_ok c P l : (PsubC P c)@l == P@l - [c].
Lemma PmulC_aux_ok c P l : (PmulC_aux P c)@l == P@l * [c].
Lemma PmulC_ok c P l : (PmulC P c)@l == P@l * [c].
Lemma Popp_ok P l : (--P)@l == - P@l.
Hint Rewrite PaddC_ok PsubC_ok PmulC_ok Popp_ok : Esimpl.
Lemma PaddX_ok P' P k l :
(forall P l, (P++P')@l == P@l + P'@l) ->
(PaddX Padd P' k P) @ l == P@l + P'@l * (hd l)^k.
Lemma Padd_ok P' P l : (P ++ P')@l == P@l + P'@l.
Lemma PsubX_ok P' P k l :
(forall P l, (P--P')@l == P@l - P'@l) ->
(PsubX Psub P' k P) @ l == P@l - P'@l * (hd l)^k.
Lemma Psub_ok P' P l : (P -- P')@l == P@l - P'@l.
Lemma PmulI_ok P' :
(forall P l, (Pmul P P') @ l == P @ l * P' @ l) ->
forall P p l, (PmulI Pmul P' p P) @ l == P @ l * P' @ (jump p l).
Lemma Pmul_ok P P' l : (P**P')@l == P@l * P'@l.
Lemma Psquare_ok P l : (Psquare P)@l == P@l * P@l.
Lemma Mphi_morph M e1 e2 :
(forall x, e1 x = e2 x) -> M @@ e1 = M @@ e2.
Lemma Mjump_xO_tail M p l :
M @@ (jump (xO p) (tail l)) = M @@ (jump (xI p) l).
Lemma Mjump_pred_double M p l :
M @@ (jump (Pos.pred_double p) (tail l)) = M @@ (jump (xO p) l).
Lemma Mjump_add M i j l :
M @@ (jump (i + j) l) = M @@ (jump j (jump i l)).
Lemma mkZmon_ok M j l :
(mkZmon j M) @@ l == (zmon j M) @@ l.
Lemma zmon_pred_ok M j l :
(zmon_pred j M) @@ (tail l) == (zmon j M) @@ l.
Lemma mkVmon_ok M i l :
(mkVmon i M)@@l == M@@l * (hd l)^i.
Ltac destr_mfactor R S := match goal with
| H : context [MFactor ?P _] |- context [MFactor ?P ?M] =>
specialize (H M); destruct MFactor as (R,S)
end.
Lemma Mphi_ok P M l :
let (Q,R) := MFactor P M in
P@l == Q@l + M@@l * R@l.
Lemma POneSubst_ok P1 M1 P2 P3 l :
POneSubst P1 M1 P2 = Some P3 -> M1@@l == P2@l ->
P1@l == P3@l.
Lemma PNSubst1_ok n P1 M1 P2 l :
M1@@l == P2@l -> P1@l == (PNSubst1 P1 M1 P2 n)@l.
Lemma PNSubst_ok n P1 M1 P2 l P3 :
PNSubst P1 M1 P2 n = Some P3 -> M1@@l == P2@l -> P1@l == P3@l.
Fixpoint MPcond (LM1: list (Mon * Pol)) (l: Env R) : Prop :=
match LM1 with
| cons (M1,P2) LM2 => (M1@@l == P2@l) /\ MPcond LM2 l
| _ => True
end.
Lemma PSubstL1_ok n LM1 P1 l :
MPcond LM1 l -> P1@l == (PSubstL1 P1 LM1 n)@l.
Lemma PSubstL_ok n LM1 P1 P2 l :
PSubstL P1 LM1 n = Some P2 -> MPcond LM1 l -> P1@l == P2@l.
Lemma PNSubstL_ok m n LM1 P1 l :
MPcond LM1 l -> P1@l == (PNSubstL P1 LM1 m n)@l.
evaluation of polynomial expressions towards R
Definition mk_X j := mkPinj_pred j mkX.
evaluation of polynomial expressions towards R
Fixpoint PEeval (l:Env R) (pe:PExpr) : R :=
match pe with
| PEc c => phi c
| PEX j => nth j l
| PEadd pe1 pe2 => (PEeval l pe1) + (PEeval l pe2)
| PEsub pe1 pe2 => (PEeval l pe1) - (PEeval l pe2)
| PEmul pe1 pe2 => (PEeval l pe1) * (PEeval l pe2)
| PEopp pe1 => - (PEeval l pe1)
| PEpow pe1 n => rpow (PEeval l pe1) (Cp_phi n)
end.
Correctness proofs
Lemma mkX_ok p l : nth p l == (mk_X p) @ l.
Hint Rewrite Padd_ok Psub_ok : Esimpl.
Section POWER.
Variable subst_l : Pol -> Pol.
Fixpoint Ppow_pos (res P:Pol) (p:positive) : Pol :=
match p with
| xH => subst_l (res ** P)
| xO p => Ppow_pos (Ppow_pos res P p) P p
| xI p => subst_l ((Ppow_pos (Ppow_pos res P p) P p) ** P)
end.
Definition Ppow_N P n :=
match n with
| N0 => P1
| Npos p => Ppow_pos P1 P p
end.
Lemma Ppow_pos_ok l :
(forall P, subst_l P@l == P@l) ->
forall res P p, (Ppow_pos res P p)@l == res@l * (pow_pos Pmul P p)@l.
Lemma Ppow_N_ok l :
(forall P, subst_l P@l == P@l) ->
forall P n, (Ppow_N P n)@l == (pow_N P1 Pmul P n)@l.
End POWER.
Normalization and rewriting
Section NORM_SUBST_REC.
Variable n : nat.
Variable lmp:list (Mon*Pol).
Let subst_l P := PNSubstL P lmp n n.
Let Pmul_subst P1 P2 := subst_l (Pmul P1 P2).
Let Ppow_subst := Ppow_N subst_l.
Fixpoint norm_aux (pe:PExpr) : Pol :=
match pe with
| PEc c => Pc c
| PEX j => mk_X j
| PEadd (PEopp pe1) pe2 => Psub (norm_aux pe2) (norm_aux pe1)
| PEadd pe1 (PEopp pe2) =>
Psub (norm_aux pe1) (norm_aux pe2)
| PEadd pe1 pe2 => Padd (norm_aux pe1) (norm_aux pe2)
| PEsub pe1 pe2 => Psub (norm_aux pe1) (norm_aux pe2)
| PEmul pe1 pe2 => Pmul (norm_aux pe1) (norm_aux pe2)
| PEopp pe1 => Popp (norm_aux pe1)
| PEpow pe1 n => Ppow_N (fun p => p) (norm_aux pe1) n
end.
Definition norm_subst pe := subst_l (norm_aux pe).
Internally, norm_aux is expanded in a large number of cases. To speed-up proofs, we use an alternative definition.
Definition get_PEopp pe :=
match pe with
| PEopp pe' => Some pe'
| _ => None
end.
Lemma norm_aux_PEadd pe1 pe2 :
norm_aux (PEadd pe1 pe2) =
match get_PEopp pe1, get_PEopp pe2 with
| Some pe1', _ => (norm_aux pe2) -- (norm_aux pe1')
| None, Some pe2' => (norm_aux pe1) -- (norm_aux pe2')
| None, None => (norm_aux pe1) ++ (norm_aux pe2)
end.
Lemma norm_aux_PEopp pe :
match get_PEopp pe with
| Some pe' => norm_aux pe = -- (norm_aux pe')
| None => True
end.
Lemma norm_aux_spec l pe :
PEeval l pe == (norm_aux pe)@l.
End NORM_SUBST_REC.
End MakeRingPol.