[isabelle-dev] [isabelle] Tiny minor backward-compatible changes to IFOL

Lawrence Paulson lp15 at cam.ac.uk
Mon Apr 27 13:08:18 CEST 2020

I have only recently proved a result of this sort, and thinking back, the need to write out

	!x y. P x & P y —> x=y

has always been one of my pet bugbears.

I don’t think a fancy symbol is needed for something that will be fairly lightly used however.


> On 27 Apr 2020, at 11:58, Tobias Nipkow <nipkow at in.tum.de> wrote:
> I don't recall feeling the need for it, although I may just be too used to what we have to conceive of notions beyond. But I have (almost) never seen it anywhere else. There are of course the counting quantifiers.
> Having said that, I wouldn't object to an "at most one" quantifier provided it has a decent syntax. See https://math.stackexchange.com/questions/1205464/quantifier-for-there-is-at-most-one

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