start on graded R-modules

algebra/graded.hlean

@@ -1,7 +1,65 @@
-/-
-Copyright (c) 2016 Egbert Rijke. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Egbert Rijke
+/- Graded modules -/
 
-Graded modules and rings.
--/
+-- Author: Floris van Doorn
+
+import ..algebra.module
+
+open algebra eq left_module pointed function equiv is_equiv is_trunc prod
+
+namespace left_module
+
+definition graded (str : Type) (I : Type) : Type := I → str
+definition graded_module (R : Ring) : Type → Type := graded (LeftModule R)
+
+variables {R : Ring} {I : Type} {M M₁ M₂ M₃ : graded_module R I}
+
+structure graded_module_hom (M₁ M₂ : graded_module R I) : Type :=
+mk' ::  (d : I → I)
+        (fn : Π⦃i j : I⦄ (p : d i = j), M₁ i →lm M₂ j)
+
+abbreviation degree := @graded_module_hom.d
+attribute graded_module_hom.fn [coercion]
+
+definition graded_module_hom.mk {M₁ M₂ : graded_module R I} (d : I → I)
+  (fn : Πi, M₁ i →lm M₂ (d i)) : graded_module_hom M₁ M₂ :=
+graded_module_hom.mk' d (λi j p, homomorphism_of_eq (ap M₂ p) ∘lm fn i)
+
+notation M₁ ` →gm ` M₂ := graded_module_hom M₁ M₂
+
+-- definition graded_module_hom (d : I → I) (M₁ M₂ : graded_module R I) : Type :=
+-- Π⦃i j : I⦄ (p : d i = j), M₁ i →lm M₂ j
+exit
+-- notation M₁ ` →[` d `] ` M₂ := graded_module_hom d M₁ M₂
+variables {d d' d₁ d₂ d₃ : I → I} {f' : M₂ →[d'] M₃} {f : M₁ →[d] M₂} {f₁ : M₁ →[d₁] M₂}
+          {f₂ : M₁ →[d₂] M₂} {f₃ : M₁ →[d₃] M₂}
+
+definition graded_module_hom_ap (f : M₁ →[d] M₂) {i : I} (x : M₁ i) : M₂ (d i) :=
+f idp x
+
+abbreviation gap := @graded_module_hom_ap
+
+definition is_exact_gmod (f : M₁ →[d] M₂) (f' : M₂ →[d'] M₃) : Type :=
+Π{i j k} (p : d i = j) (q : d' j = k), is_exact_mod (f p) (f' q)
+
+structure exact_couple (M₁ M₂ : graded_module R I) : Type :=
+  (di dj dk : I → I)
+  ( i : M₁ →[di] M₁) (j : M₁ →[dj] M₂) (k : M₂ →[dk] M₁)
+  ( exact_ij : is_exact_gmod i j)
+  ( exact_jk : is_exact_gmod j k)
+  ( exact_ki : is_exact_gmod k i)
+
+  variables {di dj dk : I → I}
+            {i : M₁ →[di] M₁} {j : M₁ →[dj] M₂} {k : M₂ →[dk] M₁}
+            ( exact_ij : is_exact_gmod i j)
+            ( exact_jk : is_exact_gmod j k)
+            ( exact_ki : is_exact_gmod k i)
+
+  namespace derived_couple
+
+  definition d : graded_module_hom _ M₂ M₂ :=
+  _
+
+  end derived_couple
+
+
+end left_module

algebra/module.hlean

@@ -8,7 +8,7 @@ Modules prod vector spaces over a ring.
 (We use "left_module," which is more precise, because "module" is a keyword.)
 -/
 import algebra.field ..move_to_lib
-open is_trunc pointed function sigma eq algebra
+open is_trunc pointed function sigma eq algebra prod is_equiv equiv
 
 structure has_scalar [class] (F V : Type) :=
 (smul : F → V → V)
@@ -219,6 +219,108 @@ section
   end
 end
 
+  section
+  variables {M M₁ M₂ M₃ : LeftModule R}
+  definition to_respect_zero (φ : M₁ →lm M₂) : φ 0 = 0 :=
+  respect_zero φ
+
+  definition is_exact_mod (f : M₁ →lm M₂) (f' : M₂ →lm M₃) : Type :=
+  @is_exact M₁ M₂ M₃ (homomorphism_fn f) (homomorphism_fn f')
+
+  definition homomorphism_compose (f' : M₂ →lm M₃) (f : M₁ →lm M₂) : M₁ →lm M₃ :=
+  homomorphism.mk (f' ∘ f) !is_module_hom_comp
+
+  variable (M)
+  definition homomorphism_id [constructor] [refl] : M →lm M :=
+  homomorphism.mk (@id M) !is_module_hom_id
+  variable {M}
+
+  abbreviation lmid [constructor] := homomorphism_id M
+  infixr ` ∘lm `:75 := homomorphism_compose
+
+  structure isomorphism (M₁ M₂ : LeftModule R) :=
+    (to_hom : M₁ →lm M₂)
+    (is_equiv_to_hom : is_equiv to_hom)
+
+  infix ` ≃lm `:25 := isomorphism
+  attribute isomorphism.to_hom [coercion]
+  attribute isomorphism.is_equiv_to_hom [instance]
+  attribute isomorphism._trans_of_to_hom [unfold 4]
+
+  definition equiv_of_isomorphism [constructor] (φ : M₁ ≃lm M₂) : M₁ ≃ M₂ :=
+  equiv.mk φ !isomorphism.is_equiv_to_hom
+
+  definition pequiv_of_isomorphism [constructor] (φ : M₁ ≃lm M₂) : M₁ ≃* M₂ :=
+  pequiv_of_equiv (equiv_of_isomorphism φ) (to_respect_zero φ)
+
+  definition LeftModule.struct2 [instance] (M : LeftModule R) : left_module R M :=
+  LeftModule.struct M
+
+  definition homomorphism.mk' (φ : M₁ → M₂) (p : Π(g₁ g₂ : M₁), φ (g₁ + g₂) = φ g₁ + φ g₂)
+    (q : Π(r : R) x, φ (r • x) = r • φ x) : M₁ →lm M₂ :=
+  homomorphism.mk φ (p, q)
+
+  definition isomorphism_of_equiv [constructor] (φ : M₁ ≃ M₂)
+    (p : Π(g₁ g₂ : M₁), φ (g₁ + g₂) = φ g₁ + φ g₂)
+    (q : Πr x, φ (r • x) = r • φ x) : M₁ ≃lm M₂ :=
+  isomorphism.mk (homomorphism.mk φ (p, q)) !to_is_equiv
+
+  definition isomorphism_of_eq [constructor] {M₁ M₂ : LeftModule R} (p : M₁ = M₂ :> LeftModule R)
+    : M₁ ≃lm M₂ :=
+  isomorphism_of_equiv (equiv_of_eq (ap LeftModule.carrier p))
+    begin intros, induction p, reflexivity end
+    begin intros, induction p, reflexivity end
+
+  -- definition pequiv_of_isomorphism_of_eq {M₁ M₂ : LeftModule R} (p : M₁ = M₂ :> LeftModule R) :
+  --   pequiv_of_isomorphism (isomorphism_of_eq p) = pequiv_of_eq (ap pType_of_LeftModule p) :=
+  -- begin
+  --   induction p,
+  --   apply pequiv_eq,
+  --   fapply pmap_eq,
+  --   { intro g, reflexivity},
+  --   { apply is_prop.elim}
+  -- end
+
+  definition to_ginv [constructor] (φ : M₁ ≃lm M₂) : M₂ →lm M₁ :=
+  homomorphism.mk φ⁻¹
+    abstract begin
+    split,
+      intro g₁ g₂, apply eq_of_fn_eq_fn' φ,
+      rewrite [respect_add φ, +right_inv φ],
+      intro r x, apply eq_of_fn_eq_fn' φ,
+      rewrite [to_respect_smul φ, +right_inv φ],
+    end end
+
+  variable (M)
+  definition isomorphism.refl [refl] [constructor] : M ≃lm M :=
+  isomorphism.mk lmid !is_equiv_id
+  variable {M}
+
+  definition isomorphism.symm [symm] [constructor] (φ : M₁ ≃lm M₂) : M₂ ≃lm M₁ :=
+  isomorphism.mk (to_ginv φ) !is_equiv_inv
+
+  definition isomorphism.trans [trans] [constructor] (φ : M₁ ≃lm M₂) (ψ : M₂ ≃lm M₃) : M₁ ≃lm M₃ :=
+  isomorphism.mk (ψ ∘lm φ) !is_equiv_compose
+
+  definition isomorphism.eq_trans [trans] [constructor]
+     {M₁ M₂ : LeftModule R} {M₃ : LeftModule R} (φ : M₁ = M₂) (ψ : M₂ ≃lm M₃) : M₁ ≃lm M₃ :=
+  proof isomorphism.trans (isomorphism_of_eq φ) ψ qed
+
+  definition isomorphism.trans_eq [trans] [constructor]
+    {M₁ : LeftModule R} {M₂ M₃ : LeftModule R} (φ : M₁ ≃lm M₂) (ψ : M₂ = M₃) : M₁ ≃lm M₃ :=
+  isomorphism.trans φ (isomorphism_of_eq ψ)
+
+  postfix `⁻¹ˡᵐ`:(max + 1) := isomorphism.symm
+  infixl ` ⬝lm `:75 := isomorphism.trans
+  infixl ` ⬝lmp `:75 := isomorphism.trans_eq
+  infixl ` ⬝plm `:75 := isomorphism.eq_trans
+
+  definition homomorphism_of_eq [constructor] {M₁ M₂ : LeftModule R} (p : M₁ = M₂ :> LeftModule R)
+    : M₁ →lm M₂ :=
+  isomorphism_of_eq p
+
+  end
+
 end
 
 end left_module