feat(data/list/basic): add filter/remove_all length properties #10409
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eric-wieser
reviewed
Nov 21, 2021
eric-wieser
reviewed
Nov 21, 2021
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A note for other reviewers: CI is not running correctly here because this is running from a fork. Can someone else advise @rgreenblatt on what to do next? |
eric-wieser
reviewed
Nov 30, 2021
src/data/list/basic.lean
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| @[simp] theorem length_filter_lt_of_mem {a : α} (l : list α) : | ||
| a ∈ l → ¬p a → (filter p l).length < l.length := | ||
| begin | ||
| induction l; | ||
| simp, | ||
| intros h_in hpa, |
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| @[simp] theorem length_filter_lt_of_mem {a : α} (l : list α) : | |
| a ∈ l → ¬p a → (filter p l).length < l.length := | |
| begin | |
| induction l; | |
| simp, | |
| intros h_in hpa, | |
| @[simp] theorem length_filter_lt_of_mem {a : α} (l : list α) (ha : a ∈ l) (hpa : ¬p a) : (filter p l).length < l.length := | |
| begin | |
| induction l; | |
| simp, |
It's usually better to put hypotheses before the colon when possible.
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Sure, done.
I assume that mem_filter_of_mem (and a few other theorems) use implications like this for syntax convenience from pattern matching? Or is there some other reason?
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Not sure if these are the right names for these theorem. Also, maybe these proofs could be cleaned up?