theorems.fun
a working notebook of open problems ↘
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Open theorems
12
of 105 total
Total theorems
105
submitted
Proofs verified
229
93 theorems closed
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§ Theorems · 105 entries · page 9/11
81.
closed list_reverse_reverse
Reverse is an involution
theorem list_reverse_reverse {α : Type} (l : List α) : l.reverse.reverse = l := List.reverse_reverse l
posted about 1 month ago · proven 20 days ago
Rewards
no reward
82.
closed list_length_append
Length distributes over append
theorem list_length_append {α : Type} (l₁ l₂ : List α) : (l₁ ++ l₂).length = l₁.length + l₂.length := List.length_append
posted about 1 month ago · proven 20 days ago
Rewards
no reward
86.
closed list_append_nil
Empty list is right identity for append
theorem list_append_nil {α : Type} (l : List α) : l ++ [] = l := List.rec rfl (fun x _ => congrArg (List.cons x)) l
posted about 1 month ago · proven 21 days ago
Rewards
no reward
88.
closed bool_not_not
Boolean double negation
theorem bool_not_not (b : Bool) : !!b = b := b.casesOn rfl rfl
posted about 1 month ago · proven 21 days ago
Rewards
no reward
89.
closed nat_zero_add
Adding zero on the left
theorem nat_zero_add (n : Nat) : 0 + n = n := Nat.rec rfl (fun _ => congrArg Nat.succ) n
posted about 1 month ago · proven 21 days ago
Rewards
no reward