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Need inverse of LemmaCardinalityOfSetNoDuplicates #18

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robin-aws opened this issue Oct 1, 2021 · 1 comment · Fixed by #19 · May be fixed by #20
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Need inverse of LemmaCardinalityOfSetNoDuplicates #18

robin-aws opened this issue Oct 1, 2021 · 1 comment · Fixed by #19 · May be fixed by #20
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This lemma proves this implication:

  lemma LemmaCardinalityOfSetNoDuplicates<T>(s: seq<T>)
    requires HasNoDuplicates(s)
    ensures |ToSet(s)| == |s|

But the opposite implication would also be very useful:

  lemma LemmaNoDuplicatesCardinalityOfSet<T>(s: seq<T>)
    requires |ToSet(s)| == |s|
    ensures HasNoDuplicates(s)

Especially because |ToSet(s)| == |s| is much cheaper to evaluate at runtime than HasNoDuplicates(s) would be (if it was a compiled function method)
@robin-aws robin-aws self-assigned this Oct 1, 2021
@gancherj gancherj mentioned this issue Oct 3, 2021
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gancherj commented Oct 3, 2021

Created pull request. Please let me know if any style fixes are needed :)

@robin-aws robin-aws mentioned this issue Oct 3, 2021
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