Syntax Definition ciun 4921

Description: Extend class notation to include indexed union. Note: Historically (prior to 21-Oct-2005), set.mm used the notation ∪ 𝑥 ∈ 𝐴𝐵, with the same union symbol as cuni 4836. While that syntax was unambiguous, it did not allow for LALR parsing of the syntax constructions in set.mm. The new syntax uses a distinguished symbol ∪ instead of ∪ and does allow LALR parsing. Thanks to Peter Backes for suggesting this change.

Hypotheses

Ref	Expression
vx	setvar 𝑥
cA	class 𝐴
cB	class 𝐵

Assertion

Ref	Expression
ciun	class ∪ 𝑥 ∈ 𝐴 𝐵

See definition df-iun 4923 for more information.