[tlaplus] Re: WITNESS BY

[Andrew Helwer <andrew.helwer@xxxxxxxxx>]

You are correct you cannot write WITNESS x \in y BY <proof>. The proof constructs that can be followed by a nested proof are:

• THEOREM, PROPOSITION, LEMMA, & COROLLARY (at the very top level of the proof)
• SUFFICES
• CASE
• PICK

SUFFICES is probably the closest to your desired usage. I am drawing this from reading the TLA+ tree-sitter grammar here. See which ones have the optional($._proof) rule at the end.

Andrew

On Saturday, November 19, 2022 at 8:49:25 AM UTC-5 jaco...@xxxxxxxxx wrote:

Hi,

My "WITNESS x \in y" generates a proof obligation, so it would be nice to

write WITNESS x\in y BY <proof>, but as far as I understand this is not

possible. Is there a reason? Is there a general work around?

Thanks for your thoughts,
Jaco van de Pol

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