. apply Nat.lt_of_succ_lt_succ pf1
case false.pf1
α : Type u_1
β : Type u_2
f : α → β
i : Nat
ih :
  ∀ {xs : List α} {bs : List Bool} (pf1 : i < length xs) (pf2 : i < length bs),
    Unique (map f xs) →
      get bs { val := i, isLt := pf2 } = true →
        get (map f xs) { val := i, isLt := (_ : i < length (map f xs)) } ∈ map f (sieve bs xs)
xs✝ : List α
bs✝ : List Bool
hu✝ : Unique (map f xs✝)
bs : List Bool
x : α
xs : List α
hnmem : ¬f x ∈ map f xs
hu : Unique (map f xs)
pf1 : Nat.succ i < length (x :: xs)
pf2 : Nat.succ i < length (false :: bs)
hget : get bs { val := i, isLt := (_ : Nat.succ i ≤ length bs) } = true
⊢ i < length xs

case false.hu
α : Type u_1
β : Type u_2
f : α → β
i : Nat
ih :
  ∀ {xs : List α} {bs : List Bool} (pf1 : i < length xs) (pf2 : i < length bs),
    Unique (map f xs) →
      get bs { val := i, isLt := pf2 } = true →
        get (map f xs) { val := i, isLt := (_ : i < length (map f xs)) } ∈ map f (sieve bs xs)
xs✝ : List α
bs✝ : List Bool
hu✝ : Unique (map f xs✝)
bs : List Bool
x : α
xs : List α
hnmem : ¬f x ∈ map f xs
hu : Unique (map f xs)
pf1 : Nat.succ i < length (x :: xs)
pf2 : Nat.succ i < length (false :: bs)
hget : get bs { val := i, isLt := (_ : Nat.succ i ≤ length bs) } = true
⊢ Unique (map f xs)

case false.hget
α : Type u_1
β : Type u_2
f : α → β
i : Nat
ih :
  ∀ {xs : List α} {bs : List Bool} (pf1 : i < length xs) (pf2 : i < length bs),
    Unique (map f xs) →
      get bs { val := i, isLt := pf2 } = true →
        get (map f xs) { val := i, isLt := (_ : i < length (map f xs)) } ∈ map f (sieve bs xs)
xs✝ : List α
bs✝ : List Bool
hu✝ : Unique (map f xs✝)
bs : List Bool
x : α
xs : List α
hnmem : ¬f x ∈ map f xs
hu : Unique (map f xs)
pf1 : Nat.succ i < length (x :: xs)
pf2 : Nat.succ i < length (false :: bs)
hget : get bs { val := i, isLt := (_ : Nat.succ i ≤ length bs) } = true
⊢ get bs { val := i, isLt := ?false.pf2 } = true

case false.pf2
α : Type u_1
β : Type u_2
f : α → β
i : Nat
ih :
  ∀ {xs : List α} {bs : List Bool} (pf1 : i < length xs) (pf2 : i < length bs),
    Unique (map f xs) →
      get bs { val := i, isLt := pf2 } = true →
        get (map f xs) { val := i, isLt := (_ : i < length (map f xs)) } ∈ map f (sieve bs xs)
xs✝ : List α
bs✝ : List Bool
hu✝ : Unique (map f xs✝)
bs : List Bool
x : α
xs : List α
hnmem : ¬f x ∈ map f xs
hu : Unique (map f xs)
pf1 : Nat.succ i < length (x :: xs)
pf2 : Nat.succ i < length (false :: bs)
hget : get bs { val := i, isLt := (_ : Nat.succ i ≤ length bs) } = true
⊢ i < length bs
case false.hu
α : Type u_1
β : Type u_2
f : α → β
i : Nat
ih :
  ∀ {xs : List α} {bs : List Bool} (pf1 : i < length xs) (pf2 : i < length bs),
    Unique (map f xs) →
      get bs { val := i, isLt := pf2 } = true →
        get (map f xs) { val := i, isLt := (_ : i < length (map f xs)) } ∈ map f (sieve bs xs)
xs✝ : List α
bs✝ : List Bool
hu✝ : Unique (map f xs✝)
bs : List Bool
x : α
xs : List α
hnmem : ¬f x ∈ map f xs
hu : Unique (map f xs)
pf1 : Nat.succ i < length (x :: xs)
pf2 : Nat.succ i < length (false :: bs)
hget : get bs { val := i, isLt := (_ : Nat.succ i ≤ length bs) } = true
⊢ Unique (map f xs)

case false.hget
α : Type u_1
β : Type u_2
f : α → β
i : Nat
ih :
  ∀ {xs : List α} {bs : List Bool} (pf1 : i < length xs) (pf2 : i < length bs),
    Unique (map f xs) →
      get bs { val := i, isLt := pf2 } = true →
        get (map f xs) { val := i, isLt := (_ : i < length (map f xs)) } ∈ map f (sieve bs xs)
xs✝ : List α
bs✝ : List Bool
hu✝ : Unique (map f xs✝)
bs : List Bool
x : α
xs : List α
hnmem : ¬f x ∈ map f xs
hu : Unique (map f xs)
pf1 : Nat.succ i < length (x :: xs)
pf2 : Nat.succ i < length (false :: bs)
hget : get bs { val := i, isLt := (_ : Nat.succ i ≤ length bs) } = true
⊢ get bs { val := i, isLt := ?false.pf2 } = true

case false.pf2
α : Type u_1
β : Type u_2
f : α → β
i : Nat
ih :
  ∀ {xs : List α} {bs : List Bool} (pf1 : i < length xs) (pf2 : i < length bs),
    Unique (map f xs) →
      get bs { val := i, isLt := pf2 } = true →
        get (map f xs) { val := i, isLt := (_ : i < length (map f xs)) } ∈ map f (sieve bs xs)
xs✝ : List α
bs✝ : List Bool
hu✝ : Unique (map f xs✝)
bs : List Bool
x : α
xs : List α
hnmem : ¬f x ∈ map f xs
hu : Unique (map f xs)
pf1 : Nat.succ i < length (x :: xs)
pf2 : Nat.succ i < length (false :: bs)
hget : get bs { val := i, isLt := (_ : Nat.succ i ≤ length bs) } = true
⊢ i < length bs