Nuprl Lemma : l_contains-append4 0,22

T:Type, A, B, C:T List. l_contains(T;A;C)  l_contains(T;A;B @ C) 
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Definitionst  T, P  Q, x:A. B(x), (x  l), {T}, P  Q, Prop, as @ bs, P  Q, P & Q, P  Q, x. t(x), xL. P(x), l_contains(T;A;B)
Lemmasall functionality wrt iff, implies functionality wrt iff, member append, append wf, l member wf

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