|Metamath Proof Explorer
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|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.
|class ∪ 𝑥 ∈ 𝐴 𝐵
|Colors of variables: wff setvar class
|Copyright terms: Public domain