feat: injectivity lemmas for List.getElem, List.getElem?, List.getElem! and List.getD#12435
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feat: injectivity lemmas for List.getElem, List.getElem?, List.getElem! and List.getD#12435
List.getElem, List.getElem?, List.getElem! and List.getD#12435Conversation
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| rw [mem_iff_getElem?] | ||
| exact ⟨_, h₂⟩; exact ⟨_ , h₂.symm⟩ | ||
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| theorem getElem?_inj_iff {l : List α} (h₀ : i < l.length) (h₁ : List.Nodup l) : |
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From the naming convention, inj already means iff. I'm not sure whether we have a convention for non-iff injectivity lemmas, my guess is just that we usually don't even state them and immediately go for an Iff which is easy to rewrite with.
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Good point, that sounds good. I believe to remember having seen precedent for inj_iff, but perhaps that was just a library defect!
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This PR provides injectivity lemmas for
List.getElem,List.getElem?,List.getElem!andList.getD.