l3lab/ntp-mathlib huggingface dataset:
/-- Strengthening of `IsLocalization.exist_integer_multiples`:
Let `J ≠ ⊤` be an ideal in a Dedekind domain `A`, and `f ≠ 0` a finite collection
of elements of `K = Frac(A)`, then we can multiply the elements of `f` by some `a : K`
to find a collection of elements of `A` that is not completely contained in `J`. -/
theorem Ideal.exist_integer_multiples_not_mem {J : Ideal A} (hJ : J ≠ ⊤) {ι : Type*} (s : Finset ι)
    (f : ι → K) {j} (hjs : j ∈ s) (hjf : f j ≠ 0) :
    ∃ a : K,
      (∀ i ∈ s, IsLocalization.IsInteger A (a * f i)) ∧
        ∃ i ∈ s, a * f i ∉ (J : FractionalIdeal A⁰ K) := by
  -- Consider the fractional ideal `I` spanned by the `f`s.
  let I : FractionalIdeal A⁰ K := spanFinset A s f
  have hI0 : I ≠ 0 := spanFinset_ne_zero.mpr ⟨j, hjs, hjf⟩
  -- We claim the multiplier `a` we're looking for is in `I⁻¹ \ (J / I)`.
  suffices ↑J / I < I⁻¹ by
    obtain ⟨_, a, hI, hpI⟩ := SetLike.lt_iff_le_and_exists.mp this
    

Proof state:
case intro.intro.intro
R : Type u_1
A : Type u_2
K : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing A
inst✝⁴ : Field K
inst✝³ : IsDomain A
inst✝² : IsDedekindDomain A
inst✝¹ : Algebra A K
inst✝ : IsFractionRing A K
J : Ideal A
hJ : J ≠ ⊤
ι : Type u_4
s : Finset ι
f : ι → K
j : ι
hjs : j ∈ s
hjf : f j ≠ 0
I : FractionalIdeal A⁰ K := spanFinset A s f
hI0 : I ≠ 0
this : ↑J / I < I⁻¹
left✝ : ↑J / I ≤ I⁻¹
a : K
hI : a ∈ I⁻¹
hpI : a ∉ ↑J / I
⊢ ∃ a, (∀ i ∈ s, IsLocalization.IsInteger A (a * f i)) ∧ ∃ i ∈ s, a * f i ∉ ↑J

Next tactic:
rw [mem_inv_iff hI0] at hI
/-- Strengthening of `IsLocalization.exist_integer_multiples`:
Let `J ≠ ⊤` be an ideal in a Dedekind domain `A`, and `f ≠ 0` a finite collection
of elements of `K = Frac(A)`, then we can multiply the elements of `f` by some `a : K`
to find a collection of elements of `A` that is not completely contained in `J`. -/
theorem Ideal.exist_integer_multiples_not_mem {J : Ideal A} (hJ : J ≠ ⊤) {ι : Type*} (s : Finset ι)
    (f : ι → K) {j} (hjs : j ∈ s) (hjf : f j ≠ 0) :
    ∃ a : K,
      (∀ i ∈ s, IsLocalization.IsInteger A (a * f i)) ∧
        ∃ i ∈ s, a * f i ∉ (J : FractionalIdeal A⁰ K) := by
  -- Consider the fractional ideal `I` spanned by the `f`s.
  let I : FractionalIdeal A⁰ K := spanFinset A s f
  have hI0 : I ≠ 0 := spanFinset_ne_zero.mpr ⟨j, hjs, hjf⟩
  -- We claim the multiplier `a` we're looking for is in `I⁻¹ \ (J / I)`.
  suffices ↑J / I < I⁻¹ by
    obtain ⟨_, a, hI, hpI⟩ := SetLike.lt_iff_le_and_exists.mp this
    rw [mem_inv_iff hI0] at hI
    

Proof state:
case intro.intro.intro
R : Type u_1
A : Type u_2
K : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing A
inst✝⁴ : Field K
inst✝³ : IsDomain A
inst✝² : IsDedekindDomain A
inst✝¹ : Algebra A K
inst✝ : IsFractionRing A K
J : Ideal A
hJ : J ≠ ⊤
ι : Type u_4
s : Finset ι
f : ι → K
j : ι
hjs : j ∈ s
hjf : f j ≠ 0
I : FractionalIdeal A⁰ K := spanFinset A s f
hI0 : I ≠ 0
this : ↑J / I < I⁻¹
left✝ : ↑J / I ≤ I⁻¹
a : K
hI : ∀ y ∈ I, a * y ∈ 1
hpI : a ∉ ↑J / I
⊢ ∃ a, (∀ i ∈ s, IsLocalization.IsInteger A (a * f i)) ∧ ∃ i ∈ s, a * f i ∉ ↑J

Next tactic:
refine' ⟨a, fun i hi => _, _⟩
/-- Strengthening of `IsLocalization.exist_integer_multiples`:
Let `J ≠ ⊤` be an ideal in a Dedekind domain `A`, and `f ≠ 0` a finite collection
of elements of `K = Frac(A)`, then we can multiply the elements of `f` by some `a : K`
to find a collection of elements of `A` that is not completely contained in `J`. -/
theorem Ideal.exist_integer_multiples_not_mem {J : Ideal A} (hJ : J ≠ ⊤) {ι : Type*} (s : Finset ι)
    (f : ι → K) {j} (hjs : j ∈ s) (hjf : f j ≠ 0) :
    ∃ a : K,
      (∀ i ∈ s, IsLocalization.IsInteger A (a * f i)) ∧
        ∃ i ∈ s, a * f i ∉ (J : FractionalIdeal A⁰ K) := by
  -- Consider the fractional ideal `I` spanned by the `f`s.
  let I : FractionalIdeal A⁰ K := spanFinset A s f
  have hI0 : I ≠ 0 := spanFinset_ne_zero.mpr ⟨j, hjs, hjf⟩
  -- We claim the multiplier `a` we're looking for is in `I⁻¹ \ (J / I)`.
  suffices ↑J / I < I⁻¹ by
    obtain ⟨_, a, hI, hpI⟩ := SetLike.lt_iff_le_and_exists.mp this
    rw [mem_inv_iff hI0] at hI
    refine' ⟨a, fun i hi => _, _⟩
    -- By definition, `a ∈ I⁻¹` multiplies elements of `I` into elements of `1`,
    -- in other words, `a * f i` is an integer.
    · 

Proof state:
case intro.intro.intro.refine'_1
R : Type u_1
A : Type u_2
K : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing A
inst✝⁴ : Field K
inst✝³ : IsDomain A
inst✝² : IsDedekindDomain A
inst✝¹ : Algebra A K
inst✝ : IsFractionRing A K
J : Ideal A
hJ : J ≠ ⊤
ι : Type u_4
s : Finset ι
f : ι → K
j : ι
hjs : j ∈ s
hjf : f j ≠ 0
I : FractionalIdeal A⁰ K := spanFinset A s f
hI0 : I ≠ 0
this : ↑J / I < I⁻¹
left✝ : ↑J / I ≤ I⁻¹
a : K
hI : ∀ y ∈ I, a * y ∈ 1
hpI : a ∉ ↑J / I
i : ι
hi : i ∈ s
⊢ IsLocalization.IsInteger A (a * f i)

Next tactic:
exact (mem_one_iff _).mp (hI (f i) (Submodule.subset_span (Set.mem_image_of_mem f hi)))
/-- Strengthening of `IsLocalization.exist_integer_multiples`:
Let `J ≠ ⊤` be an ideal in a Dedekind domain `A`, and `f ≠ 0` a finite collection
of elements of `K = Frac(A)`, then we can multiply the elements of `f` by some `a : K`
to find a collection of elements of `A` that is not completely contained in `J`. -/
theorem Ideal.exist_integer_multiples_not_mem {J : Ideal A} (hJ : J ≠ ⊤) {ι : Type*} (s : Finset ι)
    (f : ι → K) {j} (hjs : j ∈ s) (hjf : f j ≠ 0) :
    ∃ a : K,
      (∀ i ∈ s, IsLocalization.IsInteger A (a * f i)) ∧
        ∃ i ∈ s, a * f i ∉ (J : FractionalIdeal A⁰ K) := by
  -- Consider the fractional ideal `I` spanned by the `f`s.
  let I : FractionalIdeal A⁰ K := spanFinset A s f
  have hI0 : I ≠ 0 := spanFinset_ne_zero.mpr ⟨j, hjs, hjf⟩
  -- We claim the multiplier `a` we're looking for is in `I⁻¹ \ (J / I)`.
  suffices ↑J / I < I⁻¹ by
    obtain ⟨_, a, hI, hpI⟩ := SetLike.lt_iff_le_and_exists.mp this
    rw [mem_inv_iff hI0] at hI
    refine' ⟨a, fun i hi => _, _⟩
    -- By definition, `a ∈ I⁻¹` multiplies elements of `I` into elements of `1`,
    -- in other words, `a * f i` is an integer.
    · exact (mem_one_iff _).mp (hI (f i) (Submodule.subset_span (Set.mem_image_of_mem f hi)))
    · 

Proof state:
case intro.intro.intro.refine'_2
R : Type u_1
A : Type u_2
K : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing A
inst✝⁴ : Field K
inst✝³ : IsDomain A
inst✝² : IsDedekindDomain A
inst✝¹ : Algebra A K
inst✝ : IsFractionRing A K
J : Ideal A
hJ : J ≠ ⊤
ι : Type u_4
s : Finset ι
f : ι → K
j : ι
hjs : j ∈ s
hjf : f j ≠ 0
I : FractionalIdeal A⁰ K := spanFinset A s f
hI0 : I ≠ 0
this : ↑J / I < I⁻¹
left✝ : ↑J / I ≤ I⁻¹
a : K
hI : ∀ y ∈ I, a * y ∈ 1
hpI : a ∉ ↑J / I
⊢ ∃ i ∈ s, a * f i ∉ ↑J

Next tactic:
contrapose! hpI
/-- Strengthening of `IsLocalization.exist_integer_multiples`:
Let `J ≠ ⊤` be an ideal in a Dedekind domain `A`, and `f ≠ 0` a finite collection
of elements of `K = Frac(A)`, then we can multiply the elements of `f` by some `a : K`
to find a collection of elements of `A` that is not completely contained in `J`. -/
theorem Ideal.exist_integer_multiples_not_mem {J : Ideal A} (hJ : J ≠ ⊤) {ι : Type*} (s : Finset ι)
    (f : ι → K) {j} (hjs : j ∈ s) (hjf : f j ≠ 0) :
    ∃ a : K,
      (∀ i ∈ s, IsLocalization.IsInteger A (a * f i)) ∧
        ∃ i ∈ s, a * f i ∉ (J : FractionalIdeal A⁰ K) := by
  -- Consider the fractional ideal `I` spanned by the `f`s.
  let I : FractionalIdeal A⁰ K := spanFinset A s f
  have hI0 : I ≠ 0 := spanFinset_ne_zero.mpr ⟨j, hjs, hjf⟩
  -- We claim the multiplier `a` we're looking for is in `I⁻¹ \ (J / I)`.
  suffices ↑J / I < I⁻¹ by
    obtain ⟨_, a, hI, hpI⟩ := SetLike.lt_iff_le_and_exists.mp this
    rw [mem_inv_iff hI0] at hI
    refine' ⟨a, fun i hi => _, _⟩
    -- By definition, `a ∈ I⁻¹` multiplies elements of `I` into elements of `1`,
    -- in other words, `a * f i` is an integer.
    · exact (mem_one_iff _).mp (hI (f i) (Submodule.subset_span (Set.mem_image_of_mem f hi)))
    · contrapose! hpI
      -- And if all `a`-multiples of `I` are an element of `J`,
      -- then `a` is actually an element of `J / I`, contradiction.
      

Proof state:
case intro.intro.intro.refine'_2
R : Type u_1
A : Type u_2
K : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing A
inst✝⁴ : Field K
inst✝³ : IsDomain A
inst✝² : IsDedekindDomain A
inst✝¹ : Algebra A K
inst✝ : IsFractionRing A K
J : Ideal A
hJ : J ≠ ⊤
ι : Type u_4
s : Finset ι
f : ι → K
j : ι
hjs : j ∈ s
hjf : f j ≠ 0
I : FractionalIdeal A⁰ K := spanFinset A s f
hI0 : I ≠ 0
this : ↑J / I < I⁻¹
left✝ : ↑J / I ≤ I⁻¹
a : K
hI : ∀ y ∈ I, a * y ∈ 1
hpI : ∀ i ∈ s, a * f i ∈ ↑J
⊢ a ∈ ↑J / I

Next tactic:
refine' (mem_div_iff_of_nonzero hI0).mpr fun y hy => Submodule.span_induction hy _ _ _ _
/-- Strengthening of `IsLocalization.exist_integer_multiples`:
Let `J ≠ ⊤` be an ideal in a Dedekind domain `A`, and `f ≠ 0` a finite collection
of elements of `K = Frac(A)`, then we can multiply the elements of `f` by some `a : K`
to find a collection of elements of `A` that is not completely contained in `J`. -/
theorem Ideal.exist_integer_multiples_not_mem {J : Ideal A} (hJ : J ≠ ⊤) {ι : Type*} (s : Finset ι)
    (f : ι → K) {j} (hjs : j ∈ s) (hjf : f j ≠ 0) :
    ∃ a : K,
      (∀ i ∈ s, IsLocalization.IsInteger A (a * f i)) ∧
        ∃ i ∈ s, a * f i ∉ (J : FractionalIdeal A⁰ K) := by
  -- Consider the fractional ideal `I` spanned by the `f`s.
  let I : FractionalIdeal A⁰ K := spanFinset A s f
  have hI0 : I ≠ 0 := spanFinset_ne_zero.mpr ⟨j, hjs, hjf⟩
  -- We claim the multiplier `a` we're looking for is in `I⁻¹ \ (J / I)`.
  suffices ↑J / I < I⁻¹ by
    obtain ⟨_, a, hI, hpI⟩ := SetLike.lt_iff_le_and_exists.mp this
    rw [mem_inv_iff hI0] at hI
    refine' ⟨a, fun i hi => _, _⟩
    -- By definition, `a ∈ I⁻¹` multiplies elements of `I` into elements of `1`,
    -- in other words, `a * f i` is an integer.
    · exact (mem_one_iff _).mp (hI (f i) (Submodule.subset_span (Set.mem_image_of_mem f hi)))
    · contrapose! hpI
      -- And if all `a`-multiples of `I` are an element of `J`,
      -- then `a` is actually an element of `J / I`, contradiction.
      refine' (mem_div_iff_of_nonzero hI0).mpr fun y hy => Submodule.span_induction hy _ _ _ _
      · 

Proof state:
case intro.intro.intro.refine'_2.refine'_1
R : Type u_1
A : Type u_2
K : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing A
inst✝⁴ : Field K
inst✝³ : IsDomain A
inst✝² : IsDedekindDomain A
inst✝¹ : Algebra A K
inst✝ : IsFractionRing A K
J : Ideal A
hJ : J ≠ ⊤
ι : Type u_4
s : Finset ι
f : ι → K
j : ι
hjs : j ∈ s
hjf : f j ≠ 0
I : FractionalIdeal A⁰ K := spanFinset A s f
hI0 : I ≠ 0
this : ↑J / I < I⁻¹
left✝ : ↑J / I ≤ I⁻¹
a : K
hI : ∀ y ∈ I, a * y ∈ 1
hpI : ∀ i ∈ s, a * f i ∈ ↑J
y : K
hy : y ∈ I
⊢ ∀ x ∈ f '' ↑s, a * x ∈ ↑J

Next tactic:
rintro _ ⟨i, hi, rfl⟩
/-- Strengthening of `IsLocalization.exist_integer_multiples`:
Let `J ≠ ⊤` be an ideal in a Dedekind domain `A`, and `f ≠ 0` a finite collection
of elements of `K = Frac(A)`, then we can multiply the elements of `f` by some `a : K`
to find a collection of elements of `A` that is not completely contained in `J`. -/
theorem Ideal.exist_integer_multiples_not_mem {J : Ideal A} (hJ : J ≠ ⊤) {ι : Type*} (s : Finset ι)
    (f : ι → K) {j} (hjs : j ∈ s) (hjf : f j ≠ 0) :
    ∃ a : K,
      (∀ i ∈ s, IsLocalization.IsInteger A (a * f i)) ∧
        ∃ i ∈ s, a * f i ∉ (J : FractionalIdeal A⁰ K) := by
  -- Consider the fractional ideal `I` spanned by the `f`s.
  let I : FractionalIdeal A⁰ K := spanFinset A s f
  have hI0 : I ≠ 0 := spanFinset_ne_zero.mpr ⟨j, hjs, hjf⟩
  -- We claim the multiplier `a` we're looking for is in `I⁻¹ \ (J / I)`.
  suffices ↑J / I < I⁻¹ by
    obtain ⟨_, a, hI, hpI⟩ := SetLike.lt_iff_le_and_exists.mp this
    rw [mem_inv_iff hI0] at hI
    refine' ⟨a, fun i hi => _, _⟩
    -- By definition, `a ∈ I⁻¹` multiplies elements of `I` into elements of `1`,
    -- in other words, `a * f i` is an integer.
    · exact (mem_one_iff _).mp (hI (f i) (Submodule.subset_span (Set.mem_image_of_mem f hi)))
    · contrapose! hpI
      -- And if all `a`-multiples of `I` are an element of `J`,
      -- then `a` is actually an element of `J / I`, contradiction.
      refine' (mem_div_iff_of_nonzero hI0).mpr fun y hy => Submodule.span_induction hy _ _ _ _
      · rintro _ ⟨i, hi, rfl⟩; 

Proof state:
case intro.intro.intro.refine'_2.refine'_1.intro.intro
R : Type u_1
A : Type u_2
K : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing A
inst✝⁴ : Field K
inst✝³ : IsDomain A
inst✝² : IsDedekindDomain A
inst✝¹ : Algebra A K
inst✝ : IsFractionRing A K
J : Ideal A
hJ : J ≠ ⊤
ι : Type u_4
s : Finset ι
f : ι → K
j : ι
hjs : j ∈ s
hjf : f j ≠ 0
I : FractionalIdeal A⁰ K := spanFinset A s f
hI0 : I ≠ 0
this : ↑J / I < I⁻¹
left✝ : ↑J / I ≤ I⁻¹
a : K
hI : ∀ y ∈ I, a * y ∈ 1
hpI : ∀ i ∈ s, a * f i ∈ ↑J
y : K
hy : y ∈ I
i : ι
hi : i ∈ ↑s
⊢ a * f i ∈ ↑J

Next tactic:
exact hpI i hi
/-- Strengthening of `IsLocalization.exist_integer_multiples`:
Let `J ≠ ⊤` be an ideal in a Dedekind domain `A`, and `f ≠ 0` a finite collection
of elements of `K = Frac(A)`, then we can multiply the elements of `f` by some `a : K`
to find a collection of elements of `A` that is not completely contained in `J`. -/
theorem Ideal.exist_integer_multiples_not_mem {J : Ideal A} (hJ : J ≠ ⊤) {ι : Type*} (s : Finset ι)
    (f : ι → K) {j} (hjs : j ∈ s) (hjf : f j ≠ 0) :
    ∃ a : K,
      (∀ i ∈ s, IsLocalization.IsInteger A (a * f i)) ∧
        ∃ i ∈ s, a * f i ∉ (J : FractionalIdeal A⁰ K) := by
  -- Consider the fractional ideal `I` spanned by the `f`s.
  let I : FractionalIdeal A⁰ K := spanFinset A s f
  have hI0 : I ≠ 0 := spanFinset_ne_zero.mpr ⟨j, hjs, hjf⟩
  -- We claim the multiplier `a` we're looking for is in `I⁻¹ \ (J / I)`.
  suffices ↑J / I < I⁻¹ by
    obtain ⟨_, a, hI, hpI⟩ := SetLike.lt_iff_le_and_exists.mp this
    rw [mem_inv_iff hI0] at hI
    refine' ⟨a, fun i hi => _, _⟩
    -- By definition, `a ∈ I⁻¹` multiplies elements of `I` into elements of `1`,
    -- in other words, `a * f i` is an integer.
    · exact (mem_one_iff _).mp (hI (f i) (Submodule.subset_span (Set.mem_image_of_mem f hi)))
    · contrapose! hpI
      -- And if all `a`-multiples of `I` are an element of `J`,
      -- then `a` is actually an element of `J / I`, contradiction.
      refine' (mem_div_iff_of_nonzero hI0).mpr fun y hy => Submodule.span_induction hy _ _ _ _
      · rintro _ ⟨i, hi, rfl⟩; exact hpI i hi
      · 

Proof state:
case intro.intro.intro.refine'_2.refine'_2
R : Type u_1
A : Type u_2
K : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing A
inst✝⁴ : Field K
inst✝³ : IsDomain A
inst✝² : IsDedekindDomain A
inst✝¹ : Algebra A K
inst✝ : IsFractionRing A K
J : Ideal A
hJ : J ≠ ⊤
ι : Type u_4
s : Finset ι
f : ι → K
j : ι
hjs : j ∈ s
hjf : f j ≠ 0
I : FractionalIdeal A⁰ K := spanFinset A s f
hI0 : I ≠ 0
this : ↑J / I < I⁻¹
left✝ : ↑J / I ≤ I⁻¹
a : K
hI : ∀ y ∈ I, a * y ∈ 1
hpI : ∀ i ∈ s, a * f i ∈ ↑J
y : K
hy : y ∈ I
⊢ a * 0 ∈ ↑J

Next tactic:
rw [mul_zero]
/-- Strengthening of `IsLocalization.exist_integer_multiples`:
Let `J ≠ ⊤` be an ideal in a Dedekind domain `A`, and `f ≠ 0` a finite collection
of elements of `K = Frac(A)`, then we can multiply the elements of `f` by some `a : K`
to find a collection of elements of `A` that is not completely contained in `J`. -/
theorem Ideal.exist_integer_multiples_not_mem {J : Ideal A} (hJ : J ≠ ⊤) {ι : Type*} (s : Finset ι)
    (f : ι → K) {j} (hjs : j ∈ s) (hjf : f j ≠ 0) :
    ∃ a : K,
      (∀ i ∈ s, IsLocalization.IsInteger A (a * f i)) ∧
        ∃ i ∈ s, a * f i ∉ (J : FractionalIdeal A⁰ K) := by
  -- Consider the fractional ideal `I` spanned by the `f`s.
  let I : FractionalIdeal A⁰ K := spanFinset A s f
  have hI0 : I ≠ 0 := spanFinset_ne_zero.mpr ⟨j, hjs, hjf⟩
  -- We claim the multiplier `a` we're looking for is in `I⁻¹ \ (J / I)`.
  suffices ↑J / I < I⁻¹ by
    obtain ⟨_, a, hI, hpI⟩ := SetLike.lt_iff_le_and_exists.mp this
    rw [mem_inv_iff hI0] at hI
    refine' ⟨a, fun i hi => _, _⟩
    -- By definition, `a ∈ I⁻¹` multiplies elements of `I` into elements of `1`,
    -- in other words, `a * f i` is an integer.
    · exact (mem_one_iff _).mp (hI (f i) (Submodule.subset_span (Set.mem_image_of_mem f hi)))
    · contrapose! hpI
      -- And if all `a`-multiples of `I` are an element of `J`,
      -- then `a` is actually an element of `J / I`, contradiction.
      refine' (mem_div_iff_of_nonzero hI0).mpr fun y hy => Submodule.span_induction hy _ _ _ _
      · rintro _ ⟨i, hi, rfl⟩; exact hpI i hi
      · rw [mul_zero]; 

Proof state:
case intro.intro.intro.refine'_2.refine'_2
R : Type u_1
A : Type u_2
K : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing A
inst✝⁴ : Field K
inst✝³ : IsDomain A
inst✝² : IsDedekindDomain A
inst✝¹ : Algebra A K
inst✝ : IsFractionRing A K
J : Ideal A
hJ : J ≠ ⊤
ι : Type u_4
s : Finset ι
f : ι → K
j : ι
hjs : j ∈ s
hjf : f j ≠ 0
I : FractionalIdeal A⁰ K := spanFinset A s f
hI0 : I ≠ 0
this : ↑J / I < I⁻¹
left✝ : ↑J / I ≤ I⁻¹
a : K
hI : ∀ y ∈ I, a * y ∈ 1
hpI : ∀ i ∈ s, a * f i ∈ ↑J
y : K
hy : y ∈ I
⊢ 0 ∈ ↑J

Next tactic:
exact Submodule.zero_mem _
/-- Strengthening of `IsLocalization.exist_integer_multiples`:
Let `J ≠ ⊤` be an ideal in a Dedekind domain `A`, and `f ≠ 0` a finite collection
of elements of `K = Frac(A)`, then we can multiply the elements of `f` by some `a : K`
to find a collection of elements of `A` that is not completely contained in `J`. -/
theorem Ideal.exist_integer_multiples_not_mem {J : Ideal A} (hJ : J ≠ ⊤) {ι : Type*} (s : Finset ι)
    (f : ι → K) {j} (hjs : j ∈ s) (hjf : f j ≠ 0) :
    ∃ a : K,
      (∀ i ∈ s, IsLocalization.IsInteger A (a * f i)) ∧
        ∃ i ∈ s, a * f i ∉ (J : FractionalIdeal A⁰ K) := by
  -- Consider the fractional ideal `I` spanned by the `f`s.
  let I : FractionalIdeal A⁰ K := spanFinset A s f
  have hI0 : I ≠ 0 := spanFinset_ne_zero.mpr ⟨j, hjs, hjf⟩
  -- We claim the multiplier `a` we're looking for is in `I⁻¹ \ (J / I)`.
  suffices ↑J / I < I⁻¹ by
    obtain ⟨_, a, hI, hpI⟩ := SetLike.lt_iff_le_and_exists.mp this
    rw [mem_inv_iff hI0] at hI
    refine' ⟨a, fun i hi => _, _⟩
    -- By definition, `a ∈ I⁻¹` multiplies elements of `I` into elements of `1`,
    -- in other words, `a * f i` is an integer.
    · exact (mem_one_iff _).mp (hI (f i) (Submodule.subset_span (Set.mem_image_of_mem f hi)))
    · contrapose! hpI
      -- And if all `a`-multiples of `I` are an element of `J`,
      -- then `a` is actually an element of `J / I`, contradiction.
      refine' (mem_div_iff_of_nonzero hI0).mpr fun y hy => Submodule.span_induction hy _ _ _ _
      · rintro _ ⟨i, hi, rfl⟩; exact hpI i hi
      · rw [mul_zero]; exact Submodule.zero_mem _
      · 

Proof state:
case intro.intro.intro.refine'_2.refine'_3
R : Type u_1
A : Type u_2
K : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing A
inst✝⁴ : Field K
inst✝³ : IsDomain A
inst✝² : IsDedekindDomain A
inst✝¹ : Algebra A K
inst✝ : IsFractionRing A K
J : Ideal A
hJ : J ≠ ⊤
ι : Type u_4
s : Finset ι
f : ι → K
j : ι
hjs : j ∈ s
hjf : f j ≠ 0
I : FractionalIdeal A⁰ K := spanFinset A s f
hI0 : I ≠ 0
this : ↑J / I < I⁻¹
left✝ : ↑J / I ≤ I⁻¹
a : K
hI : ∀ y ∈ I, a * y ∈ 1
hpI : ∀ i ∈ s, a * f i ∈ ↑J
y : K
hy : y ∈ I
⊢ ∀ (x y : K), a * x ∈ ↑J → a * y ∈ ↑J → a * (x + y) ∈ ↑J

Next tactic:
intro x y hx hy
/-- Strengthening of `IsLocalization.exist_integer_multiples`:
Let `J ≠ ⊤` be an ideal in a Dedekind domain `A`, and `f ≠ 0` a finite collection
of elements of `K = Frac(A)`, then we can multiply the elements of `f` by some `a : K`
to find a collection of elements of `A` that is not completely contained in `J`. -/
theorem Ideal.exist_integer_multiples_not_mem {J : Ideal A} (hJ : J ≠ ⊤) {ι : Type*} (s : Finset ι)
    (f : ι → K) {j} (hjs : j ∈ s) (hjf : f j ≠ 0) :
    ∃ a : K,
      (∀ i ∈ s, IsLocalization.IsInteger A (a * f i)) ∧
        ∃ i ∈ s, a * f i ∉ (J : FractionalIdeal A⁰ K) := by
  -- Consider the fractional ideal `I` spanned by the `f`s.
  let I : FractionalIdeal A⁰ K := spanFinset A s f
  have hI0 : I ≠ 0 := spanFinset_ne_zero.mpr ⟨j, hjs, hjf⟩
  -- We claim the multiplier `a` we're looking for is in `I⁻¹ \ (J / I)`.
  suffices ↑J / I < I⁻¹ by
    obtain ⟨_, a, hI, hpI⟩ := SetLike.lt_iff_le_and_exists.mp this
    rw [mem_inv_iff hI0] at hI
    refine' ⟨a, fun i hi => _, _⟩
    -- By definition, `a ∈ I⁻¹` multiplies elements of `I` into elements of `1`,
    -- in other words, `a * f i` is an integer.
    · exact (mem_one_iff _).mp (hI (f i) (Submodule.subset_span (Set.mem_image_of_mem f hi)))
    · contrapose! hpI
      -- And if all `a`-multiples of `I` are an element of `J`,
      -- then `a` is actually an element of `J / I`, contradiction.
      refine' (mem_div_iff_of_nonzero hI0).mpr fun y hy => Submodule.span_induction hy _ _ _ _
      · rintro _ ⟨i, hi, rfl⟩; exact hpI i hi
      · rw [mul_zero]; exact Submodule.zero_mem _
      · intro x y hx hy; 

Proof state:
case intro.intro.intro.refine'_2.refine'_3
R : Type u_1
A : Type u_2
K : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing A
inst✝⁴ : Field K
inst✝³ : IsDomain A
inst✝² : IsDedekindDomain A
inst✝¹ : Algebra A K
inst✝ : IsFractionRing A K
J : Ideal A
hJ : J ≠ ⊤
ι : Type u_4
s : Finset ι
f : ι → K
j : ι
hjs : j ∈ s
hjf : f j ≠ 0
I : FractionalIdeal A⁰ K := spanFinset A s f
hI0 : I ≠ 0
this : ↑J / I < I⁻¹
left✝ : ↑J / I ≤ I⁻¹
a : K
hI : ∀ y ∈ I, a * y ∈ 1
hpI : ∀ i ∈ s, a * f i ∈ ↑J
y✝ : K
hy✝ : y✝ ∈ I
x y : K
hx : a * x ∈ ↑J
hy : a * y ∈ ↑J
⊢ a * (x + y) ∈ ↑J

Next tactic:
rw [mul_add]
/-- Strengthening of `IsLocalization.exist_integer_multiples`:
Let `J ≠ ⊤` be an ideal in a Dedekind domain `A`, and `f ≠ 0` a finite collection
of elements of `K = Frac(A)`, then we can multiply the elements of `f` by some `a : K`
to find a collection of elements of `A` that is not completely contained in `J`. -/
theorem Ideal.exist_integer_multiples_not_mem {J : Ideal A} (hJ : J ≠ ⊤) {ι : Type*} (s : Finset ι)
    (f : ι → K) {j} (hjs : j ∈ s) (hjf : f j ≠ 0) :
    ∃ a : K,
      (∀ i ∈ s, IsLocalization.IsInteger A (a * f i)) ∧
        ∃ i ∈ s, a * f i ∉ (J : FractionalIdeal A⁰ K) := by
  -- Consider the fractional ideal `I` spanned by the `f`s.
  let I : FractionalIdeal A⁰ K := spanFinset A s f
  have hI0 : I ≠ 0 := spanFinset_ne_zero.mpr ⟨j, hjs, hjf⟩
  -- We claim the multiplier `a` we're looking for is in `I⁻¹ \ (J / I)`.
  suffices ↑J / I < I⁻¹ by
    obtain ⟨_, a, hI, hpI⟩ := SetLike.lt_iff_le_and_exists.mp this
    rw [mem_inv_iff hI0] at hI
    refine' ⟨a, fun i hi => _, _⟩
    -- By definition, `a ∈ I⁻¹` multiplies elements of `I` into elements of `1`,
    -- in other words, `a * f i` is an integer.
    · exact (mem_one_iff _).mp (hI (f i) (Submodule.subset_span (Set.mem_image_of_mem f hi)))
    · contrapose! hpI
      -- And if all `a`-multiples of `I` are an element of `J`,
      -- then `a` is actually an element of `J / I`, contradiction.
      refine' (mem_div_iff_of_nonzero hI0).mpr fun y hy => Submodule.span_induction hy _ _ _ _
      · rintro _ ⟨i, hi, rfl⟩; exact hpI i hi
      · rw [mul_zero]; exact Submodule.zero_mem _
      · intro x y hx hy; rw [mul_add]; 

Proof state:
case intro.intro.intro.refine'_2.refine'_3
R : Type u_1
A : Type u_2
K : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing A
inst✝⁴ : Field K
inst✝³ : IsDomain A
inst✝² : IsDedekindDomain A
inst✝¹ : Algebra A K
inst✝ : IsFractionRing A K
J : Ideal A
hJ : J ≠ ⊤
ι : Type u_4
s : Finset ι
f : ι → K
j : ι
hjs : j ∈ s
hjf : f j ≠ 0
I : FractionalIdeal A⁰ K := spanFinset A s f
hI0 : I ≠ 0
this : ↑J / I < I⁻¹
left✝ : ↑J / I ≤ I⁻¹
a : K
hI : ∀ y ∈ I, a * y ∈ 1
hpI : ∀ i ∈ s, a * f i ∈ ↑J
y✝ : K
hy✝ : y✝ ∈ I
x y : K
hx : a * x ∈ ↑J
hy : a * y ∈ ↑J
⊢ a * x + a * y ∈ ↑J

Next tactic:
exact Submodule.add_mem _ hx hy