[NTG-context] Re: equation to right margin

[Alan Bowen <bowenalan03@gmail.com>]

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Hi, Mikael—

In answer to your question: I am one of two editors of *Aestimatio:
Sources and Studies in the History of Science*, where the science in
question is premodern. As it turns out, our publications tend to the
history of mathematics and astronomy (Babylonian, Egyptian, Greco-Roman,
Arabic), where the math, though common enough, is pretty much limited to
arithmetical computations and trigonometry. The paper that introduced the
problem of grouping is actually a lengthy review of a book on Heron’s
*Arithmetica*.

Your exchanges with Aditya are very interesting and, for me, most
informative.

Many thanks!

Alan

On Thu, Oct 10, 2024 at 1:36 AM Mikael Sundqvist <mickep@gmail.com> wrote:

> Hi,
>
> A. Bowen: The cases are meant for when you divide something into
> cases, as in the example below with the absolute value. It is a kind
> of inline part of a formula, and I would claim that when you number an
> equation, you do not number one case of a cases, but the equation. If
> you refer to it, you talk abou "the second line in (1)" if you need to
> specify. I also get a bit curious, are you editor of some math journal
> that is typeset by ConTeXt?
>
> A. Braslau: I agree that it is common to put the brace on the left,
> but I insist that it makes more sense to put it on the right _if_ you
> have equation numbers on the right. If equation numbers are to the
> left, it makes sense to put the brace on the left. Nevertheless, to
> put the brace on the left side and numbering on the right is possible
> (see example below). But the equation number in this case is sitting
> in between the two equations, and that is disturbing. If there would
> be three lines, one could argue that it would sit on the middle one.
> Or not distinguish it from the case where it sits on the middle line.
>
> The good thing is of course that one can do as one please.
>
> \starttext
> \startformula
>   \abs{x} =
>   \startcases
>     \NC  x, \NC x > 0; \NR
>     \NC  0, \NC x = 0; \NR
>     \NC -x, \NC x < 0. \NR
>   \stopcases
>   \numberhere[eq:foo]
> \stopformula
>
> \startformula
>   \startalign
>     [location=packed,fences=cases]
>     \NC \[21-(9 - n^2)\NC =□^\prime\]\NR
>     \NC  n^2+12 \NC=□^\prime.        \NR
>   \stopalign
>   \numberhere[eq:foo]
> \stopformula
>
> \stoptext
>
> /Mikael
>
> On Thu, Oct 10, 2024 at 2:21 AM Alan Braslau via ntg-context
> <ntg-context@ntg.nl> wrote:
> >
> > It is common, when writing a system of equations, to put a brace on the
> > left. It could make sense to number this system of equations with a
> > single number, on the right and aligned with the right margin. It would
> > also make sense for this number to be aligned with the middle of the
> > two equations of the system.
> >
> > A brace on the right would not introduce the grouping as a system of
> > equations, rather as a pair of equations sharing a common number.
> >
> > Alan
> >
> >
> >
> > On Wed, 9 Oct 2024 12:20:00 -0400
> > Alan Bowen <bowenalan03@gmail.com> wrote:
> >
> > > I understand. The reasoning makes sense to me and, as editor of a
> > > paper in which this appears, I will ask the author to consider
> > > dropping the brace.
> > >
> > > I wonder of there is some similar thinking underlying the fact that
> > > \startcases... puts the equation number so close to the equation
> > > itself and not at a margin (typically right).
> > >
> > > Again, many thanks, Mikael.
> > > Alan
> > >
> > > On Wed, Oct 9, 2024 at 12:12 PM Mikael Sundqvist <mickep@gmail.com>
> > > wrote:
> > >
> > > > Hi,
> > > >
> > > > I think what you ask for was never supported in ConTeXt, for a
> > > > reason. The idea is that either one groups a set of equations with
> > > > a brace and numbers them with one number, or one does not group,
> > > > and then one can number each line separately/independently.
> > > > Grouping on the left with a brace and numbering one line to the
> > > > right is, even if we see that often, not really logical.
> > > >
> > > > If there is a large request for doing this, I can talk to Hans about
> > > > it, maybe it is easy on the code side to support it. But I remember
> > > > from when we were messing with numbering, and in particular when
> > > > there are alignments, that it is a bit complicated.
> > > >
> > > > /Mikael
> > > >
> > > > On Wed, Oct 9, 2024 at 5:19 PM Alan Bowen <bowenalan03@gmail.com>
> > > > wrote:
> > > > >
> > > > > Thank you, Mikael. That is very helpful and much appreciated.
> > > > >
> > > > > What I now have is:
> > > > > \startplaceformula
> > > > >   \startformula
> > > > >     \startalign
> > > > >       \NC \[21-(9 - n^2)\NC =□^\prime\]  \NR[eq:1]
> > > > >       \NC  n^2+12 \NC=□^\prime.          \NR[eq:2]
> > > > >     \stopalign
> > > > >   \stopformula
> > > > > \stopplaceformula
> > > > > which put the numbers at the right margin,as I wanted.
> > > > >
> > > > > So how do I get a brace on the left rather than on the right?  Or
> > > > > is
> > > > there documentation that explains this?
> > > > >
> > > > > Alan
> > > > >
> > > > > On Wed, Oct 9, 2024 at 10:22 AM Mikael Sundqvist
> > > > > <mickep@gmail.com>
> > > > wrote:
> > > > >>
> > > > >> Hi,
> > > > >>
> > > > >> On Mon, Oct 7, 2024 at 11:45 PM Alan Bowen
> > > > >> <bowenalan03@gmail.com>
> > > > wrote:
> > > > >> >
> > > > >> > I have the following which works, except for the fact that the
> > > > equation number does not go to the right margin.
> > > > >> >
> > > > >> > \startplaceformula
> > > > >> > \startformula[align=middle, prefix=no]
> > > > >> > \startcases[distance=2pt]
> > > > >> > \NC \[21-(9 - n^2)\NC =□^\prime\]\NR
> > > > >> > \NC\hfill n^2+12 \NC=□^\prime.\NR[eq04]
> > > > >> > \stopcases
> > > > >> > \stopformula
> > > > >> > \stopplaceformula
> > > > >> >
> > > > >> > I expect that I have missed something pretty basic here, so any
> > > > guidance will be greatly appreciated.
> > > > >>
> > > > >> Maybe I misunderstand you, but I do not think cases is right
> > > > >> here. Also, are you sure you want to group two equations but
> > > > >> only number one of them.
> > > > >>
> > > > >> If I understand you correctly, I'd try with one of these,
> > > > >> depending on if citing the group or one of the equations.
> > > > >>
> > > > >> \starttext
> > > > >>
> > > > >> \startformula
> > > > >>   \startalign[location=packed,fences=sesac]
> > > > >>     \NC \[21-(9 - n^2)\NC =□^\prime\]\NR
> > > > >>     \NC  n^2+12 \NC=□^\prime.        \NR
> > > > >>   \stopalign
> > > > >>   \numberhere[eq:foo]
> > > > >> \stopformula
> > > > >>
> > > > >> \startplaceformula
> > > > >>   \startformula
> > > > >>     \startalign
> > > > >>       \NC \[21-(9 - n^2)\NC =□^\prime\]  \NR%[eq:bar-a]
> > > > >>       \NC  n^2+12 \NC=□^\prime.          \NR[eq:bar-b]
> > > > >>     \stopalign
> > > > >>   \stopformula
> > > > >> \stopplaceformula
> > > > >>
> > > > >> \stoptext
> > > > >>
> > > > >> /Mikael
> > > > >>
> >
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