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Merge branch 'interior_pi' of github.com:leanprover-community/mathlib…
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… into minkowski
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alexjbest committed Aug 12, 2021
2 parents 56cba8c + ca86ca7 commit d726584
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8 changes: 4 additions & 4 deletions src/topology/bases.lean
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end

lemma interior_pi_set_subset {ι : Type*} {α : ι → Type*} [Π i, topological_space (α i)]
{I : set ι} {s : Π i, set (α i)} : interior (pi I s) ⊆ I.pi (λ i, interior (s i)) :=
(I : set ι) (s : Π i, set (α i)) : interior (pi I s) ⊆ I.pi (λ i, interior (s i)) :=
begin
intro a,
simp only [mem_pi, mem_interior_iff_mem_nhds],
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end

lemma pi_set_interior_subset {ι : Type*} [fintype ι] {α : ι → Type*} [Π i, topological_space (α i)]
{I : set ι} {s : Π i, set (α i)} : I.pi (λ i, interior (s i)) ⊆ interior (pi I s) :=
(I : set ι) (s : Π i, set (α i)) : I.pi (λ i, interior (s i)) ⊆ interior (pi I s) :=
begin
intro a,
simp only [mem_pi, mem_interior_iff_mem_nhds],
refine set_pi_mem_nhds (finite.of_fintype _),
end

lemma interior_pi_set {ι : Type*} [fintype ι] {α : ι → Type*} [Π i, topological_space (α i)]
{I : set ι} {s : Π i, set (α i)} : interior (pi I s) = I.pi (λ i, interior (s i)) :=
eq_of_subset_of_subset interior_pi_set_subset (subset_interior_pi I s)
(I : set ι) (s : Π i, set (α i)) : interior (pi I s) = I.pi (λ i, interior (s i)) :=
eq_of_subset_of_subset (interior_pi_set_subset I s) (pi_set_interior_subset I s)

/-- If `α` is a separable space and `f : α → β` is a continuous map with dense range, then `β` is
a separable space as well. E.g., the completion of a separable uniform space is separable. -/
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