! in front of a relation symbol R should be equivalent to \not R

[christianp]

A student using AsciiMath recently needed to write something equivalent to the LaTeX \not \subset. As far as I can tell, AsciiMath doesn't currently have a generic not syntax to draw a line through the following symbol.

There are a couple of constants defined this way already: !in and !=.

In christianp/asciimath2tex#4, I've separated out the built-in constants that act like relations, and added a rule to the grammar that says if they're preceded by a ! character, put a \not in front of the TeX output.

The MathML 3 spec contains an operator dictionary; I suppose everything in that list that has a "not" variant should follow this rule.

Might this lead to breaking changes? I suppose a statement like 5!le120 would fall foul of this, so you'd have to insist on a space: 5! le 120.

[davidfarmer]

There already is an ambiguity between 5! = 120 and 5 != 120,
so this suggestion does not break anything. Personally, I like the idea
of using spaces to clarify the meaning.

However, I think it is better to just identify the small number of missing
"not"ed relations, and just implement them specifically. The ones I see as
important are subset, superset, and equiv. Maybe if you used the successor
relations (which I never do) then you might possibly want to negate them.

Another missing relation is "proper subset", which is \subsetneq in
TeX (it is sube with a slash only through the lower part).

If everyone used sub to mean "subset and possibly equal to", then
we would never need to use sube, and then !sube could convert to
\subsetneq. But I don't see people liking that.

Maybe subne is a reasonable option?

[christianp]

Good point about spacing!

\nexists is another symbol the student needed. You're right that the subset relations are the most commonly used, but we might as well add at least the successor relations. I can see someone using the logical entailment and operators, too.

Is there a philosophy of minimalism behind the number of constants in AsciiMath, or are things just added as needed?

[pkra]

If I may be so bold: The W3C MathOnWeb CG has a dormant task force on "text based" formats and I think you might find more people interested in standardization in the group.

(FYI Joining a call does not require formally joining the group, you can just show up - but maybe give us a heads-up.)

[davidfarmer]

Thanks for the suggestion. I joined the W3C MathOnWeb CG. I assume I will receive announcements of calls and other activities. It is a shame that the Text-based math group is not active. I think AsciiMath is a good start, and we are working on allowing that type of markup in PreTeXt.

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On Thu, 31 Jan 2019, Peter Krautzberger wrote: If I may be so bold: The W3C MathOnWeb CG has a dormant task force on "text based" formats and I think you might find more people interested in standardization in the group. (FYI Joining a call does not require formally joining the group, you can just show up - but maybe give us a heads-up.) — You are receiving this because you commented. Reply to this email directly, view it on GitHub, or mute the thread.[AAM6LFzezlsTgj9C5ZeblXWsYPiZDASYks5vIrUVgaJpZM4aX5hm.gif]

[davidfarmer]

Is there a philosophy of minimalism behind the number of constants in AsciiMath, or are things just added as needed?

I was not involved in the design of AsciiMath, so I cannot comment on its philosophy. But I do think it is good for AsciiMath to be very rigid and explicitly encode exactly what is allowed. If you want to have complete flexibility, then use LaTeX. I see AsciiMath as being able to handle a limited range of mathematics extremely well. Maybe not all undergrad (and lower) math, but a lot of it. Here is an example for why "!" should not always convert to "\not" in TeX. Suppose we want to use AsciiMath for elementary number theory. A fundamental relationship is "divides", as in 6|90 (six divides ninety, meaning that ninety/six is a whole number). The notation in TeX is commonly written the same (although that is not actually correct. See https://tex.stackexchange.com/questions/498/mid-vertical-bar-vert-lvert-rvert-divides and elsewhere) 7 does not divide 90. How would you write that? A reasonable AsciiMath markup is 7!|90 However, 7\not|90 looks terrible in TeX. Replacing the "|" by the correct command still looks bad. You have to write 7\nmid90 to have it look good in TeX. My point is that "!" would not always translate to "\not", even if you wanted to have a different approach to processing AsciiMath to TeX.