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lean4game/server/adam/Adam/Levels/LinearAlgebra/N09_Prod.lean

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import Adam.Metadata
import Mathlib.Algebra.Module.Submodule.Lattice
import Mathlib.Data.Real.Basic
import Mathlib.LinearAlgebra.Span
Game "Adam"
World "Module2"
Level 9
Title "Lineare Abbildung"
Introduction
"
"
universe u
variable {K : Type u} [Field K]
variable {ι : Type u} {V : ι → Type u}
variable [∀i, AddCommMonoid (V i)] [∀i, Module K (V i)]
/-
Ein externes Summe von Vektorräumen schreibt man mit `\Pi\0`, also `Π₀ i, V i`.
Das Suffix `_₀` wird in Mathlib häufig dafür verwendet "endlichen Support" zu bezeichnen.
-/
example : Module K (Π₀ i, V i) := inferInstance
variable {U : Type u} [AddCommMonoid U] [Module K U]
Statement
"" : True := by
sorry
-- -- :(
-- variable [decidable_eq ι]
-- variable [Π (i : ι) (x : V i), decidable (x ≠ 0)]
-- def my_sum_map (f : Π i, V i →ₗ[K] U) : (Π₀ i, V i) →ₗ[K] U :=
-- { to_fun := λ x, x.sum (λ i, (f i)),
-- map_add' :=
-- begin
-- intros,
-- funext,
-- sorry,
-- end,
-- map_smul' :=
-- begin
-- intros,
-- funext,
-- simp,
-- sorry
-- end }
-- Statement
-- "Sei `U` ein `K`-Vektorraum und `fᵢ : Vᵢ → U` eine Familie von `K`-lineare Abbildungen
-- in `K`-Vektorräume. Dann gibt es genau eine Abbildung `f : (Π₀ i, V i) → U`, die mit
-- allen kommutiert."
-- (f : ∀ i, V i →ₗ[K] U) :
-- ∃! (g : (Π₀ i, V i) →ₗ[K] U), (∀ i v, f i v = g (dfinsupp.single i v)) :=
-- by
-- let g := my_sum_map f,
-- use g,
-- constructor,
-- { simp,
-- intros,
-- sorry },
-- { intros g' h,
-- apply linear_map.ext,
-- intro x,
-- sorry
-- -- change (λ i, g' x i) = λ i, f i x, -- Wieso?
-- -- funext,
-- -- symmetry,
-- -- apply h,
-- }