2014-08-01 17:37:55 +00:00
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logic.classes
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=============
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Useful classes for general logical manipulations.
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* [inhabited](inhabited.lean) : inhabited types
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2014-08-17 21:41:23 +00:00
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* [nonempty](nonempty.lean) : nonempty type
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2014-08-01 17:37:55 +00:00
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* [decidable](decidable.lean) : decidable types
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2014-08-17 21:41:23 +00:00
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* [congr](congr.lean) : congruences with respect to suitable relations
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Constructively, inhabited types have a witness, while nonempty types
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are "proof irrelevant". Classically (assuming the axiom in
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`logic.axioms.hilbert`) the two are equivalent. Type class inferences
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are set up to use "inhabited" however, so users should use that to
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declare that types have an element. Use "nonempty" in the hypothesis
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of a theorem when the theorem does not depend on the witness chosen.
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