|
| 1 | +Require Import ssreflect ssrfun. |
| 2 | +From HB Require Import structures cat. |
| 3 | + |
| 4 | +Set Implicit Arguments. |
| 5 | +Unset Strict Implicit. |
| 6 | +Unset Printing Implicit Defensive. |
| 7 | +Add Search Blacklist "__canonical__". |
| 8 | + |
| 9 | +Local Open Scope algebra_scope. |
| 10 | +Local Open Scope cat_scope. |
| 11 | + |
| 12 | +HB.mixin Record IsRing A := { |
| 13 | + zero : A; |
| 14 | + one : A; |
| 15 | + add : A -> A -> A; |
| 16 | + opp : A -> A; |
| 17 | + mul : A -> A -> A; |
| 18 | + addrA : associative add; |
| 19 | + addrC : commutative add; |
| 20 | + add0r : left_id zero add; |
| 21 | + addNr : left_inverse zero opp add; |
| 22 | + mulrA : associative mul; |
| 23 | + mul1r : left_id one mul; |
| 24 | + mulr1 : right_id one mul; |
| 25 | + mulrDl : left_distributive mul add; |
| 26 | + mulrDr : right_distributive mul add; |
| 27 | +}. |
| 28 | + |
| 29 | +#[short(type="ring")] |
| 30 | +HB.structure Definition Ring := { A of IsRing A }. |
| 31 | + |
| 32 | +Bind Scope algebra_scope with Ring.sort. |
| 33 | +Notation "0" := zero : algebra_scope. |
| 34 | +Notation "1" := one : algebra_scope. |
| 35 | +Infix "+" := (@add _) : algebra_scope. |
| 36 | +Notation "- x" := (@opp _ x) : algebra_scope. |
| 37 | +Infix "*" := (@mul _) : algebra_scope. |
| 38 | +Notation "x - y" := (x + - y) : algebra_scope. |
| 39 | + |
| 40 | +Lemma addr0 (R : ring) : right_id (@zero R) add. |
| 41 | +Proof. by move=> x; rewrite addrC add0r. Qed. |
| 42 | + |
| 43 | +Lemma addrN (R : ring) : right_inverse (@zero R) opp add. |
| 44 | +Proof. by move=> x; rewrite addrC addNr. Qed. |
| 45 | + |
| 46 | +Lemma addKr (R : ring) (x : R) : cancel (add x) (add (- x)). |
| 47 | +Proof. by move=> y; rewrite addrA addNr add0r. Qed. |
| 48 | + |
| 49 | +Lemma addrI (R : ring) (x : R) : injective (add x). |
| 50 | +Proof. exact: can_inj (addKr _). Qed. |
| 51 | + |
| 52 | +Lemma opprK (R : ring) : involutive (@opp R). |
| 53 | +Proof. by move=> x; apply: (@addrI _ (- x)); rewrite addNr addrN. Qed. |
| 54 | + |
| 55 | +HB.mixin Record IsRingHom (A B : ring) (f : A -> B) := { |
| 56 | + hom1_subproof : f 1%A = 1%A; |
| 57 | + homB_subproof : {morph f : x y / x - y}; |
| 58 | + homM_subproof : {morph f : x y / (x * y)%A}; |
| 59 | +}. |
| 60 | + |
| 61 | +HB.structure Definition RingHom A B := { f of IsRingHom A B f }. |
| 62 | + |
| 63 | +Lemma id_IsRingHom A : IsRingHom A A idfun. Proof. by []. Defined. |
| 64 | +HB.instance Definition _ A := id_IsRingHom A. |
| 65 | + |
| 66 | +Lemma comp_IsRingHom (A B C : ring) |
| 67 | + (f : RingHom.type A B) (g : RingHom.type B C) : |
| 68 | + IsRingHom A C (f \; g :> U). |
| 69 | +Proof. |
| 70 | +by constructor => [|x y|x y]; |
| 71 | +rewrite /comp/= ?hom1_subproof ?homB_subproof ?homM_subproof. |
| 72 | +Qed. |
| 73 | +HB.instance Definition _ A B C f g := @comp_IsRingHom A B C f g. |
| 74 | + |
| 75 | +HB.instance Definition _ := IsQuiver.Build ring RingHom.type. |
| 76 | +HB.instance Definition _ := |
| 77 | + Quiver_IsPreCat.Build ring (fun _ => idfun) (fun _ _ _ f g => f \; g :> U). |
| 78 | +HB.instance Definition _ := Quiver_IsPreConcrete.Build ring (fun _ _ => id). |
| 79 | +Lemma ring_precat : PreConcrete_IsConcrete ring. |
| 80 | +Proof. |
| 81 | +constructor => A B [f cf] [g cg]//=; rewrite -[_ = _]/(f = g) => fg. |
| 82 | +case: _ / fg in cg *; congr {|RingHom.sort := _ ; RingHom.class := _|}. |
| 83 | +case: cf cg => [[? ? ?]] [[? ? ?]]. |
| 84 | +by congr RingHom.Class; congr IsRingHom.phant_Build => //=; apply: Prop_irrelevance. |
| 85 | +Qed. |
| 86 | +HB.instance Definition _ := ring_precat. |
| 87 | + |
| 88 | +Lemma ring_IsCat : PreCat_IsCat ring. |
| 89 | +Proof. |
| 90 | +by constructor=> [A B f|A B f|A B C D f g h]; exact: concrete_fun_inj. |
| 91 | +Qed. |
| 92 | +HB.instance Definition _ := ring_IsCat. |
| 93 | + |
| 94 | +Lemma hom1 (R S : ring) (f : R ~> S) : f 1%A = 1%A. |
| 95 | +Proof. exact: hom1_subproof. Qed. |
| 96 | +Lemma homB (R S : ring) (f : R ~> S) : {morph f : x y / x - y}. |
| 97 | +Proof. exact: homB_subproof. Qed. |
| 98 | +Lemma homM (R S : ring) (f : R ~> S) : {morph f : x y / (x * y)%A}. |
| 99 | +Proof. exact: homM_subproof. Qed. |
| 100 | +Lemma hom0 (R S : ring) (f : R ~> S) : f 0%A = 0%A. |
| 101 | +Proof. by rewrite -(addrN 1%A) homB addrN. Qed. |
| 102 | +Lemma homN (R S : ring) (f : R ~> S) : {morph f : x / - x}. |
| 103 | +Proof. by move=> x; rewrite -[- x]add0r homB hom0 add0r. Qed. |
| 104 | +Lemma homD (R S : ring) (f : R ~> S) : {morph f : x y / x + y}. |
| 105 | +Proof. by move=> x y; rewrite -[y]opprK !homB !homN. Qed. |
| 106 | + |
| 107 | +HB.mixin Record IsIdeal (R : ring) (I : R -> Prop) := { |
| 108 | + ideal0 : I 0; |
| 109 | + idealD : forall x y, I x -> I y -> I (x + y); |
| 110 | + idealM : forall x y, I y -> I (x * y)%A; |
| 111 | +}. |
| 112 | +HB.structure Definition Ideal (R : ring) := { I of IsIdeal R I }. |
| 113 | + |
| 114 | +HB.mixin Record Ideal_IsPrime (R : ring) (I : R -> Prop) of IsIdeal R I := { |
| 115 | + ideal_prime : forall x y : R, I (x * y)%A -> I x \/ I y |
| 116 | +}. |
| 117 | +#[short(type="spectrum")] |
| 118 | +HB.structure Definition PrimeIdeal (R : ring) := |
| 119 | + { I of Ideal_IsPrime R I & Ideal R I }. |
| 120 | + |
0 commit comments