Def @i always.P(v) == e@i.P((x when e))

is mentioned by

Thm* es:ES, i,x:Id, T:Type, I:(TProp). Thm* (vartype(i;x) r T) & e@i.first(e)  I((x when e)) Thm*  Thm* e@i.I((x when e))  I((x after e))  @i always.I(x)

[es-invariant1]

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