[seqfan] Re: Style sheet lacks much of anything on "vertical bar"

[Robert Munafo]

Let's not go too far with explicit rules here, I'm more towards
David's response. Maybe it's a bad idea to explicitly state what "|"
is used for because that would make people think we're implicitly
discouraging anything else.

I would imagine that there would be a general rule, somewhere between
the top of the "Spelling and Notation" section and the end of the
"Grammar" paragraph, that would say:

   Express things in an unambiguous way, and when necessary, make it
clear with brackets, parentheses, explanatory text, etc. as needed.
This might apply, for example, when using a non-associative relation
multiple times in a row, or multiple uses of a symbol that has
multiple meanings.

But in fact I see no guideline like that. I think this is because it's
obvious enough that there is a problem, and it gets fixed in editing.
Mike's example of cardinality, "such that" and "divides"  all at once,
would surely be noticed and discouraged on the spot.

I didn't say much about all the strange stuff I found, merely what I
think are the common existing uses. I just found Mma code in A057877%t
that appears to use || as logical "or" (disjunction) so I guess I was
too quick to speak against that use. Also, there are a ton of good
sequences that break whatever rules we might write, rare uses like
Dirac bra-ket notation in A268759%C, partitioning of sets as in
A274871%e, literal graphical use as in A264962%e and A249762%e, the
labour of love that is A263267%e, and so many Pentomino diagrams, you
get the idea.

--
  Robert Munafo, mrob27 at gmail.com

On Thu, Mar 28, 2024 at 4:37 AM David Sycamore via SeqFan
<seqfan at list.seqfan.eu> wrote:
 > I agree that three different uses of “|” in the same statement is
overdoing it, and may lead to confusion. [...] In case of any doubt
the best fallback is to “spell it out in full in plain English”.
[Nothing] wrong with that

On 28 Mar 2024, at 05:39, mike at vincico.com wrote:
 > [...]  [Suppose that] "Number of primes p such that p divides k but
p is coprime to n." [were] poorly expressed [as]   |{ p | p | k, (p,
n) = 1 }|   [...]