Replace ℤ with an extra type parameter.

For now, we probably want to build on top of this limited to ℕ anyway.

Author: eric-wieser

src/geometric_algebra/nursery/graded.lean

@@ -3,15 +3,17 @@ import algebra.group
 import linear_algebra.tensor_product
 import tactic.ring
 
-universes u
+universes u v
 
 open_locale big_operators
 open_locale classical
 open finset
 
 class graded_module_components
+  -- the indices of the grades, typically ℕ
+  {ι : Type u} [has_zero ι]
   -- a type for each grade.
-  (A : ℤ → Type u)
+  (A : ι → Type u)
 := 
   -- (A 0) is the scalar type
   [zc: comm_ring (A 0)]
@@ -25,21 +27,23 @@ attribute [instance] graded_module_components.b
 attribute [instance] graded_module_components.c
 
 namespace graded_module_components
-  variables {A : ℤ → Type u}
+  variables {ι : Type u} [has_zero ι] {A : ι → Type u}
   /-- objects are coercible only if they have the same grade-/
-  instance has_coe (r s : ℕ) (h: r = s) : has_coe (A r) (A s) := { coe := by {subst h, exact id}}
+  instance has_coe (r s : ι) (h: r = s) : has_coe (A r) (A s) := { coe := by {subst h, exact id}}
 end graded_module_components
 
 -- needed for the definition of `select`
 attribute [instance] dfinsupp.to_semimodule
 
 /-- Grade selection maps from objects in G to a finite set of components of substituent grades -/
 class has_grade_select
-  (A : ℤ → Type u) (G: Type u)
+  {ι : Type u} [has_zero ι]
+  (A : ι → Type u) (G: Type u)
   [graded_module_components A]
   [add_comm_group G]
+  [ring (A 0)]
   [module (A 0) G] :=
-(select : G →ₗ[A 0] (Π₀ r, A r))
+(select : linear_map (A 0) G (Π₀ r, A r))
 
 /- TODO: check precedence -/
 notation `⟨`:0 g`⟩_`:0 r:100 := has_grade_select.select g r
@@ -51,7 +55,8 @@ notation `⟨`:0 g`⟩_`:0 r:100 := has_grade_select.select g r
 /-- A module divisible into disjoint graded modules, where the grade selectio
     operator is a complete and independent set of projections -/
 class graded_module
-  (A : ℤ → Type u) (G: Type u)
+  {ι : Type v} [has_zero ι]
+  (A : ι → Type u) (G: Type u)
   [graded_module_components A]
   [add_comm_group G]
   [module (A 0) G]
@@ -61,42 +66,42 @@ class graded_module
 
 
 namespace graded_module
-  variables {A : ℤ → Type u} {G: Type u}
+  variables {ι : Type v}  [has_zero ι] {A : ι → Type u} {G: Type u}
   variables [graded_module_components A] [add_comm_group G] [module (A 0) G]
   variables [graded_module A G]
 
   /-- locally bind the notation above to our A and G-/
-  local notation `⟨`:0 g`⟩_`:0 r:100 := @has_grade_select.select A G _ _ _ _ g r
+  local notation `⟨`:0 g`⟩_`:0 r:100 := @has_grade_select.select ι A G _ _ _ _ g r
 
   /-- convert from r-vectors to multi-vectors -/
-  instance has_coe (r : ℤ) : has_coe (A r) G := { coe := to_fun }
+  instance has_coe (r : ι) : has_coe (A r) G := { coe := to_fun }
 
   @[simp]
-  lemma coe_def {r : ℤ} (v : A r) : (v : G) = to_fun v := rfl
+  lemma coe_def {r : ι} (v : A r) : (v : G) = to_fun v := rfl
 
   /-- An r-vector has only a single grade
       Discussed at https://leanprover.zulipchat.com/#narrow/stream/113489-new-members/topic/Expressing.20a.20sum.20with.20finitely.20many.20nonzero.20terms/near/202657281-/
-  lemma select_coe_is_single {r : ℤ} (v : A r) : has_grade_select.select (v : G) = dfinsupp.single r v := begin
+  lemma select_coe_is_single {r : ι} (v : A r) : has_grade_select.select (v : G) = dfinsupp.single r v := begin
     symmetry,
     rw is_complete (v : G) (dfinsupp.single r v),
     symmetry,
     apply dfinsupp.sum_single_index,
     exact linear_map.map_zero _,
   end
 
-  def is_r_vector (r : ℤ) (a : G) := (⟨a⟩_r : G) = a
+  def is_r_vector (r : ι) (a : G) := (⟨a⟩_r : G) = a
 
   /-- Chisholm 6a, ish.
       This says A = ⟨A}_r for r-vectors.
       Chisholm aditionally wants proof that A != ⟨A}_r for non-rvectors -/
-  lemma r_grade_of_coe {r : ℤ} (v : A r) : ⟨v⟩_r = v := begin
+  lemma r_grade_of_coe {r : ι} (v : A r) : ⟨v⟩_r = v := begin
     rw select_coe_is_single,
     rw dfinsupp.single_apply,
     simp,
   end
 
   /-- to_fun is injective -/
-  lemma to_fun_inj (r : ℤ) : function.injective (to_fun : A r → G) := begin
+  lemma to_fun_inj (r : ι) : function.injective (to_fun : A r → G) := begin
     intros a b h,
     rw ← r_grade_of_coe a,
     rw ← r_grade_of_coe b,
@@ -106,13 +111,13 @@ namespace graded_module
   end
 
   /-- Chisholm 6b -/
-  lemma grade_of_sum (r : ℤ) (a b : G) : ⟨a + b⟩_r = ⟨a⟩_r + ⟨b⟩_r := by simp
+  lemma grade_of_sum (r : ι) (a b : G) : ⟨a + b⟩_r = ⟨a⟩_r + ⟨b⟩_r := by simp
 
   /-- Chisholm 6c -/
-  lemma grade_smul (r : ℤ) (k : A 0) (a : G) : ⟨k • a⟩_r = k • ⟨a⟩_r := by simp
+  lemma grade_smul (r : ι) (k : A 0) (a : G) : ⟨k • a⟩_r = k • ⟨a⟩_r := by simp
 
   /-- chisholm 6d. Modifid to use `_s` instead of `_r` on the right, to keep the statement cast-free -/
-  lemma grade_grade (r s : ℤ) (a : G) : ⟨⟨a⟩_r⟩_s = if r = s then ⟨a⟩_s else 0
+  lemma grade_grade (r s : ι) (a : G) : ⟨⟨a⟩_r⟩_s = if r = s then ⟨a⟩_s else 0
   := begin
     rw select_coe_is_single,
     rw dfinsupp.single_apply,