[Merged by Bors] - feat(data/option/basic): lemmas on map of none and congr #5424
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pechersky
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Dec 18, 2020
pechersky
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bryangingechen
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| @@ -106,6 +106,18 @@ by cases x; simp | |||
| x.map f = some b ↔ ∃ a, x = some a ∧ f a = b := | |||
| by cases x; simp | |||
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| lemma map_eq_none {α β} {x : option α} {f : α → β} : | |||
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| lemma map_eq_none {α β} {x : option α} {f : α → β} : | |
| @[simp] lemma map_eq_none {α β} {x : option α} {f : α → β} : |
like below? Or is there a reason not to?
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simp linter complains if both are simp afair.
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eric-wieser
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Dec 19, 2020
| by { cases x; simp only [map_none', map_some', eq_self_iff_true] } | ||
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| lemma map_congr {f g : α → β} {x : option α} (h : ∀ a ∈ x, f a = g a) : | ||
| option.map f x = option.map g x := |
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I think this lemma would be better if you left it without the x in the result (and maybe also the hypothesis. If you do that, then you can claim that map is injective
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How would you phrase the hypothesis then? I've found this lemma useful for the cases when x is some complex expression, and f a = g a for all some a for that complex x, but not in the general case.
There's already an option.map_injective lemma.
pechersky
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LGTM. bors merge |
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Pull request successfully merged into master. Build succeeded: |
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