is mentioned by

Def member-left-paren(x,y.E(x;y);i;s) == (xs.InjCase(x; a. E(a;i), false))	[member-left-paren]
Def member-right-paren(x,y.E(x;y);i;s) == (xs.InjCase(x; a. false, E(a;i)))	[member-right-paren]

In prior sections: bool 1 sqequal 1 prog 1 mb basic union list 1 graph 1 1

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