feat(data/set/basic): decidable_mem #9733
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kmill
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eric-wieser
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Oct 15, 2021
| def decidable_mem {α : Type u} {β : Type v} [has_mem α β] (s : β) := | ||
| decidable_pred (∈ s) | ||
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| instance decidable_mem_of (p : α → Prop) [H : decidable_pred p] : decidable_mem {a | p a} := H |
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| instance decidable_mem_of (p : α → Prop) [H : decidable_pred p] : decidable_mem {a | p a} := H | |
| instance decidable_mem_set_of (p : α → Prop) [H : decidable_pred p] : decidable_mem {a | p a} := H |
since {a | p a} is syntax for set_of p
eric-wieser
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Oct 15, 2021
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I'm somewhat ambivalent on this. I don't think there's much readability gain, but I also don't think this is likely to cause any problems since the other decidable predicates seem not to have either.
Presumably we should have classical.dec_mem to match classical.dec_pred etc?
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decidable_mem sisdecidable_pred (∈ s). It can save parentheses, is a bit easier to read, and makes it less tempting to break the set API.Right now this is just a test to see how it works.