feat: lemmas about List.tail #5360
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nomeata
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Sep 16, 2024
| The number of elements satisfying a predicate in a sublist is at least the number of elements satisfying the predicate in the list, | ||
| minus the difference in the lengths. | ||
| -/ | ||
| theorem Sublist.le_countP (s : l₁ <+ l₂) (p) : countP p l₂ - (l₂.length - l₁.length) ≤ countP p l₁ := by |
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Maybe avoiding Nat.sub, since that is the general advise, isn’t it?
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| theorem Sublist.le_countP (s : l₁ <+ l₂) (p) : countP p l₂ - (l₂.length - l₁.length) ≤ countP p l₁ := by | |
| theorem Sublist.le_countP (s : l₁ <+ l₂) (p) : countP p l₂ + l₁.length ≤ countP p l₁ + l₂.length := by |
(This is based on a suggestion by @jcommelin on a somewhat similar lemma of mine in leanprover-community/mathlib4#15383 (comment))
But I agree that reads much less natural that way.
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Yeah, I trust in omega for things like this.
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…19874) Makes `tail_reverse_eq_reverse_dropLast` a deprecated alias to [`tail_reverse`](https://github.com/leanprover/lean4/blob/938651121f3d8819109eee75722a1de087feff71/src/Init/Data/List/Lemmas.lean#L2990-L2994), which was added to core in leanprover/lean4#5360. This duplicated lemma was found by [`tryAtEachStep`](https://github.com/dwrensha/tryAtEachStep).
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