Stream: Archive Mirror: Isabelle Users Mailing List

Topic: [isabelle] Definition of Max on finite sets


view this post on Zulip Email Gateway (Aug 19 2022 at 10:23):

From: Christoph LANGE <math.semantic.web@gmail.com>
Dear all,

let me document one Q&A here, as I'm travelling and stackexchange
doesn't have an offline mode, unlike email.

In a private conversation I had asked:

How is "Max {}" defined? I find the definition of "Max = foldl max" strange anyway, as there is no base-case argument for foldl.

And Makarius answered:

Note that it is fold1 (fold-one). It is intended for non-empty finite sets. So it will do the right thing under that assumption. Otherwise it is also defined, but it might produce non-sense, or we just don't know about what it produces.

@Makarius: Thanks for pointing out the difference between "one" and
"ell". These looked to similar in my font.

I don't fully understand the definition of fold1, but I'm happy to
believe that it works :-)

Cheers,

Christoph


Last updated: Mar 29 2024 at 12:28 UTC