mb event system 2 Sections EventSystems Doc
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Def act(k) == outr(k)

is mentioned by

Def act(e) == act(kind(e))[es-act]
Def kindcase(k;a.f(a);l,t.g(l;t))
Def == if islocal(k) f(act(k)) else g(lnk(k);tag(k)) fi
[kindcase]

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mb event system 2 Sections EventSystems Doc