Misplaced punctuation in display

[ksk...@gmail.com]

Somehow, it was only very recently that I discovered that in PreTeXt, when a clause or sentence ends inside a displayed equation, the punctuation is supposed to be provided outside of the display block. The logic behind this is sound (sentential punctuation is not semantically part of the math) but I disagree with the result of this example:

          <me>
              \begin{cases} 1 &amp; m = n \\ 0 &amp; m \neq n \end{cases}
          </me>.

The period is placed on the baseline of the full display; I assume this is because in LaTeX the "\text{.}" item goes just before the close of display math mode. However, in this example I think the period should end up before \end{cases}, so that the period appears on the baseline of the last line of the cases block.

There are probably similar usages that need a similar tweak to the punctuation placement model, but this is by far the most common one for me.

Kiran

[David W. Farmer]

I think that is an argument for incorrect processing of that
markup, not for violating the principle that the end of the
sentence is at the end of the "me".

Regards,

David

> --
> You received this message because you are subscribed to the Google Groups "PreTeXt support" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to
> pretext-suppo...@googlegroups.com.
> To view this discussion visithttps://groups.google.com/d/msgid/pretext-support/d33f7717-8039-45b4-a334-a985b84599b0n%40googlegroups.c
> om.
>
>

[ksk...@gmail.com]

Maybe I should clarify that I agree with the principle! This example just shows that implementing the principle correctly is a bit tricky; it was meant to be a bug report.

Kiran

[Rob Beezer]

This is one of my favorite PreTeXt features. Observe that if you #xref a
properly-authored #me, the knowl you get has the math and no period whatsoever.

Can we just say this "needs work"? Or perhaps "is not as robust as it could be"?

Thanks for the report, Kiran. This is how we improve. I agree, in principle,
that this could be better.

Of course, one reason for PreTeXt is the futility in parsing LaTeX/TeX into more
modern output formats. And that's what we need to do here. We will have little
defense against the crazy author who ends their #me with

\end%
{cases}

But we should be able to handle more sane scenarios.

> There are probably similar usages

Do you (or anybody else) have suggestions? It'll be nearly as easy to deal with
"cases" alone as to deal with six more that are similar.

Thanks,
Rob

> visithttps://groups.google.com/d/msgid/pretext-support/d33f7717-8039-45b4-a334-a985b84599b0n%40googlegroups.c <http://groups.google.com/d/msgid/pretext-support/d33f7717-8039-45b4-a334-a985b84599b0n%40googlegroups.c>
> > om.

> >
> >
>
> --
> You received this message because you are subscribed to the Google Groups
> "PreTeXt support" group.
> To unsubscribe from this group and stop receiving emails from it, send an email
> to pretext-suppo...@googlegroups.com

> <mailto:pretext-suppo...@googlegroups.com>.
> To view this discussion visit
> https://groups.google.com/d/msgid/pretext-support/32407c7d-1a4c-436e-8e0b-910e06908b3en%40googlegroups.com <https://groups.google.com/d/msgid/pretext-support/32407c7d-1a4c-436e-8e0b-910e06908b3en%40googlegroups.com?utm_medium=email&utm_source=footer>.

[Miles Wheeler]

>> There are probably similar usages
>Do you (or anybody else) have suggestions? It'll be nearly as easy to
>deal with "cases" alone as to deal with six more that are similar.

For a differential equations course I often write things like

<me>
\left\{
\begin{alignedat}{2}
\Delta u \amp = f \amp \quad \amp \text{ in } \Omega, \\
u \amp = g \amp \quad \amp \text{ on } \partial\Omega
\end{alignedat}
\right.
</me>.

where I would want the period to end up after \partial\Omega. (If that clashes with other uses of aligned/alignedat, I'd be more than happy to manually add some hypothetical "PreTeXt punctuation goes here" command in the appropriate spot each time.)

Best,
Miles

>To view this discussion visit https://groups.google.com/d/msgid/pretext-support/MTAwMDAyOS5iZWV6ZXI.1731286432%40quikprotect.

[Rob Beezer]

Dear Miles,

Thanks very much for that example. We have support for "alignedat" as part of
the "md" element. See, for example,

Paragraph
https://pretextbook.org/examples/sample-article/html/section-mathematics.html#section-mathematics-4-7

So if you use that construction, the period at the end of the sentence gets
placed inside the final #mrow, as Kiran suggests. What does not happen is there
is no way (currently) to place the left brace to group the equations, as you
have done.

Which prompts the following:

* Is a left brace, as in Miles example, mathematically necessary, or just
customary? Is the layout of displayed math not enough to suggest the two
equations are related, or in a group? (Ignore any question of numbering
equations for the moment.)

* Do we need a #cases element (for use inside #me, #md) to produce the right
LaTeX environment, AND make placement of Kiran's period a lot more fool-proof?

* Where else do you use a LaTeX "\\" that might be better reflected in PreTeXt
markup and supplied by our conversions?

* I'll partially answer that last one: matrices. Where does the sentence-ending
period go (vertically) when display math finishes with a matrix?

Rob

[David W. Farmer]

Some people use a big left curly bracket to indicate a "system"
of equations, and some don't. Usage definitely varies by how
advanced is the author/reader, and also by location. This was
discussed extensively in the MathML working group.

So, we have to allow both options.

Regards,

David

> https://groups.google.com/d/msgid/pretext-support/MTAwMDAzNy5iZWV6ZXI.1731362014%40quikprotect.
>
>

[Rob Beezer]

Thanks, David.

On 11/11/24 14:45, David W. Farmer wrote:
> This was
> discussed extensively in the MathML working group.

And I presume the conclusion was that it was something MathML should/would support?

Back to PreTeXt.

<md group-left="brace">
<mrow>...

* Easy to implement, I think.

* Allows for @group-right (in isolation or conjunction).

* Allows for other sorts of brackets ("parenthesis").

* Goes with the entire #md, no partial notion.

* Spares the novice TeX-nician from knowing about necessity and construction of
"\right.".

* Lets us get "\text{.}" in the right place (almost forgot this bullet!).

* Workable with SpaceMath? (Space Math? with a space?)

Rob

[ksk...@gmail.com]

One further observation here: the exact situation I started with is illustrated in section 4.9.5 of the PreTeXt guide, where the current behavior is presented as a feature and not a bug. Hmm.

[Michael Shulman]

I just recently started using PreTeXt, and although in general I love its approach to display-math-ending punctuation, I have also run into this IMHO surprising and ugly behavior regarding punctuation after {cases}.  Searching the archives turned up this discussion, but it didn't seem to reach a conclusion.  Is there any prospect of putting the ending punctuation on the last line of a {cases} environment that ends the <md>?

[Rob Beezer]

Dear Michael,

Thanks for bringing this up again. Could you humor me and post the following?

1. Actual PreTeXt-generated LaTeX for an #md, w/ cases, hard up against a
period. (There are options now to get complete LaTeX source as an output format.)

2. A (minimally) edited version of (1) that you consider beautiful. I guess
with an eye to (a) parsing the "\end{cases}" and (b) reacting.

Thanks,
Rob

> --
> You received this message because you are subscribed to the Google Groups
> "PreTeXt support" group.
> To unsubscribe from this group and stop receiving emails from it, send an email
> to pretext-suppo...@googlegroups.com <mailto:pretext-

> support+u...@googlegroups.com>.

> To view this discussion visit https://groups.google.com/d/msgid/pretext-

> support/4b2405af-95b0-4e37-8e57-755d5a2f66ban%40googlegroups.com <https://
> groups.google.com/d/msgid/pretext-
> support/4b2405af-95b0-4e37-8e57-755d5a2f66ban%40googlegroups.com?
> utm_medium=email&utm_source=footer>.

[Michael Shulman]

Sure, here you go.  I would prefer the web output to be beautified too, of course.

You received this message because you are subscribed to a topic in the Google Groups "PreTeXt support" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/pretext-support/ts2Xcbkyj9k/unsubscribe.
To unsubscribe from this group and all its topics, send an email to pretext-suppo...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/pretext-support/MTAwMDAzNS5iZWV6ZXI.1768068138%40pnsh.

--

Michael Shulman

Professor of Mathematics for Humans

University of San Diego

"The role of the intellectual cannot be to excuse the violence of one
side and condemn that of the other."
        -- Albert Camus

[Rob Beezer]

Thanks. That is what I would have guessed. (For the casual reader: slide the
\text{.} prior to the \end{cases}) And the resulting PDF is not unattractive. ;-)

Might be possible, though what we do already is a bit tricky.

Web, of course, is MathJax, and we have limited control. But we ship the same
raw LaTeX to print/PDF as we do to web, just with different wrappers, so it
should come along.

Rob

On 1/10/26 10:15, 'Michael Shulman' via PreTeXt support wrote:
> Sure, here you go.  I would prefer the web output to be beautified too, of course.
>

> On Sat, Jan 10, 2026 at 10:02 AM 'Rob Beezer' via PreTeXt support <pretext-
> sup...@googlegroups.com <mailto:pretext...@googlegroups.com>> wrote:
>
> Dear Michael,
>
> Thanks for bringing this up again.  Could you humor me and post the following?
>
> 1.  Actual PreTeXt-generated LaTeX for an #md, w/ cases, hard up against a
> period.  (There are options now to get complete LaTeX source as an output
> format.)
>
> 2.  A (minimally) edited version of (1) that you consider beautiful.  I guess
> with an eye to (a) parsing the "\end{cases}" and (b) reacting.
>
> Thanks,
> Rob
>
> On 1/9/26 18:18, 'Michael Shulman' via PreTeXt support wrote:
> > I just recently started using PreTeXt, and although in general I love its
> > approach to display-math-ending punctuation, I have also run into this IMHO
> > surprising and ugly behavior regarding punctuation after {cases}.
> Searching the
> > archives turned up this discussion, but it didn't seem to reach a
> conclusion.
> > Is there any prospect of putting the ending punctuation on the last line
> of a
> > {cases} environment that ends the <md>?
> >
> > On Wednesday, January 29, 2025 at 12:40:30 PM UTC-8 ksk...@gmail.com

> support%2Bunsu...@googlegroups.com> <mailto:pretext- <mailto:pretext->
> > support+u...@googlegroups.com
> <mailto:support%2Bunsu...@googlegroups.com>>.

> > To view this discussion visit https://groups.google.com/d/msgid/pretext-

> <https://groups.google.com/d/msgid/pretext->
> > support/4b2405af-95b0-4e37-8e57-755d5a2f66ban%40googlegroups.com
> <http://40googlegroups.com> <https://
> > groups.google.com/d/msgid/pretext- <http://groups.google.com/d/msgid/
> pretext->
> > support/4b2405af-95b0-4e37-8e57-755d5a2f66ban%40googlegroups.com
> <http://40googlegroups.com>?

> > utm_medium=email&utm_source=footer>.
>
> --
> You received this message because you are subscribed to a topic in the
> Google Groups "PreTeXt support" group.
> To unsubscribe from this topic, visit https://groups.google.com/d/topic/

> pretext-support/ts2Xcbkyj9k/unsubscribe <https://groups.google.com/d/topic/
> pretext-support/ts2Xcbkyj9k/unsubscribe>.

> To unsubscribe from this group and all its topics, send an email to pretext-

> support+u...@googlegroups.com <mailto:pretext-
> support%2Bunsu...@googlegroups.com>.

> To view this discussion visit https://groups.google.com/d/msgid/pretext-

> support/MTAwMDAzNS5iZWV6ZXI.1768068138%40pnsh <https://groups.google.com/d/
> msgid/pretext-support/MTAwMDAzNS5iZWV6ZXI.1768068138%40pnsh>.
>
>
>
> --
> Michael Shulman
> Professor of Mathematics for Humans <https://home.sandiego.edu/~shulman/humans.html>

> University of San Diego
>
> "The role of the intellectual cannot be to excuse the violence of one
> side and condemn that of the other."
>         -- Albert Camus
>

> --
> You received this message because you are subscribed to the Google Groups
> "PreTeXt support" group.
> To unsubscribe from this group and stop receiving emails from it, send an email
> to pretext-suppo...@googlegroups.com <mailto:pretext-
> support+u...@googlegroups.com>.
> To view this discussion visit https://groups.google.com/d/msgid/pretext-support/

> CADYavpxHM8z%3Dme_Mu%3D%2BtogimudVihvhC8%3D_aoWN_kKH2pNtaOw%40mail.gmail.com
> <https://groups.google.com/d/msgid/pretext-support/
> CADYavpxHM8z%3Dme_Mu%3D%2BtogimudVihvhC8%3D_aoWN_kKH2pNtaOw%40mail.gmail.com?
> utm_medium=email&utm_source=footer>.

[Michael Shulman]

Thanks for considering it!  Of course, there are additional subtleties.  For instance, if the {cases} *itself* ends with a {cases}, then the \text{.} should slide past both of them, and so on.

To unsubscribe from this topic, visit https://groups.google.com/d/topic/pretext-support/ts2Xcbkyj9k/unsubscribe.
To unsubscribe from this group and all its topics, send an email to pretext-suppo...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/pretext-support/MTAwMDAxNy5iZWV6ZXI.1768069736%40pnsh.

--

Michael Shulman

Professor of Mathematics for Humans

[Eugene Boman]

Are you using the ptx-mode.el that I sent you or did you decide to write your own?

If the former, I recently fixed some small bugs that you'll probably want to have. Let me know if you want them.

If the latter, I'd be interested in seeing what you come up with if you wouldn't mind sharing.

-- Bud

--
You received this message because you are subscribed to the Google Groups "PreTeXt support" group.
To unsubscribe from this group and stop receiving emails from it, send an email to pretext-suppo...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/pretext-support/4b2405af-95b0-4e37-8e57-755d5a2f66ban%40googlegroups.com.

[Michael Shulman]

I ended up writing my own.  Here's what I've got right now, let me know what you think!  I've been using it as I develop it, finding and fixing bugs and adding features.  Once it seems fairly stable, I'm planning to put it up on github.

You received this message because you are subscribed to a topic in the Google Groups "PreTeXt support" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/pretext-support/ts2Xcbkyj9k/unsubscribe.
To unsubscribe from this group and all its topics, send an email to pretext-suppo...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/pretext-support/7d2f2ea7-985a-475f-9edb-824ee49010e7%40gmail.com.

[Eugene Boman]

I haven't tried to use it yet but from looking it over it's clear that you are a more skillful Lisp programmer than I :-)

-- Bud

To view this discussion visit https://groups.google.com/d/msgid/pretext-support/CADYavpyNd2qoyotYZDygLE4XtmyPrRUKryQhEs%3DLfrTv9eXOTg%40mail.gmail.com.

[Rob Beezer]

Implemented now. Should be in tomorrow's "nightly" of the CLI. Holler if you
notice anything unexpected.

Only applies to an #md followed by "clause-ending punctuation" whose LaTeX
ends with a "\end{cases}". (You shouldn't be putting "cases" inside an "m".)
Much easier due to the recent improvements for #m and #md.

Nested cases environments will be a bridge too far. Ideally, in PreTeXt you
would never author LaTeX that has a \begin \end pair in it, nor would you use
\\ for a line break. Indeed it is a common authoring error to put something
like an "aligned" enviroment inside an #m element, with \\. But we are not
fanatics. Not yet, anyway. A "pmatrix" enviroment is entirely reasonable.
With \\. Plus ampersands, which is another story altogether.

Anyway, I suspect with this one case completed (pun intended), we might be able
to place punctuation better after things like matrices. So it is open season on
other ugly periods.

Rob

On 1/10/26 11:37, 'Michael Shulman' via PreTeXt support wrote:
> Thanks for considering it!  Of course, there are additional subtleties.  For
> instance, if the {cases} *itself* ends with a {cases}, then the \text{.} should
> slide past both of them, and so on.
>

> On Sat, Jan 10, 2026 at 10:29 AM 'Rob Beezer' via PreTeXt support <pretext-

> sup...@googlegroups.com <mailto:pretext...@googlegroups.com>> wrote:
>
> Thanks.  That is what I would have guessed.  (For the casual reader: slide the
> \text{.} prior to the \end{cases})  And the resulting PDF is not
> unattractive.  ;-)
>
> Might be possible, though what we do already is a bit tricky.
>
> Web, of course, is MathJax, and we have limited control.  But we ship the same
> raw LaTeX to print/PDF as we do to web, just with different wrappers, so it
> should come along.
>
> Rob
>
>
> On 1/10/26 10:15, 'Michael Shulman' via PreTeXt support wrote:
> > Sure, here you go.  I would prefer the web output to be beautified too,
> of course.
> >
> > On Sat, Jan 10, 2026 at 10:02 AM 'Rob Beezer' via PreTeXt support <pretext-

> > sup...@googlegroups.com <mailto:sup...@googlegroups.com>
> <mailto:pretext...@googlegroups.com <mailto:pretext-

> > support%2Bunsu...@googlegroups.com
> <mailto:support%252Buns...@googlegroups.com>> <mailto:pretext-
> <mailto:pretext-> <mailto:pretext- <mailto:pretext->>
> >      > support+u...@googlegroups.com
> <mailto:support%2Bunsu...@googlegroups.com>
> >     <mailto:support%2Bunsu...@googlegroups.com
> <mailto:support%252Buns...@googlegroups.com>>>.

> >      > To view this discussion visit https://groups.google.com/d/msgid/
> pretext- <https://groups.google.com/d/msgid/pretext->

> >     <https://groups.google.com/d/msgid/pretext- <https://
> groups.google.com/d/msgid/pretext->>
> >      > support/4b2405af-95b0-4e37-8e57-755d5a2f66ban%40googlegroups.com
> <http://40googlegroups.com>
> >     <http://40googlegroups.com <http://40googlegroups.com>> <https://
> >      > groups.google.com/d/msgid/pretext- <http://groups.google.com/d/
> msgid/pretext-> <http://groups.google.com/d/msgid/ <http://
> groups.google.com/d/msgid/>
> >     pretext->
> >      > support/4b2405af-95b0-4e37-8e57-755d5a2f66ban%40googlegroups.com
> <http://40googlegroups.com>
> >     <http://40googlegroups.com <http://40googlegroups.com>>?

> >      > utm_medium=email&utm_source=footer>.
> >
> >     --
> >     You received this message because you are subscribed to a topic in the
> >     Google Groups "PreTeXt support" group.
> >     To unsubscribe from this topic, visit https://groups.google.com/d/

> topic/ <https://groups.google.com/d/topic/>
> >     pretext-support/ts2Xcbkyj9k/unsubscribe <https://groups.google.com/d/
> topic/ <https://groups.google.com/d/topic/>

> >     pretext-support/ts2Xcbkyj9k/unsubscribe>.
> >     To unsubscribe from this group and all its topics, send an email to
> pretext-
> > support+u...@googlegroups.com

> <mailto:support%2Bunsu...@googlegroups.com> <mailto:pretext-
> <mailto:pretext->
> > support%2Bunsu...@googlegroups.com
> <mailto:support%252Buns...@googlegroups.com>>.

> >     To view this discussion visit https://groups.google.com/d/msgid/
> pretext- <https://groups.google.com/d/msgid/pretext->

> >     support/MTAwMDAzNS5iZWV6ZXI.1768068138%40pnsh <https://
> groups.google.com/d/ <https://groups.google.com/d/>

> >     msgid/pretext-support/MTAwMDAzNS5iZWV6ZXI.1768068138%40pnsh>.
> >
> >
> >
> > --
> > Michael Shulman
> > Professor of Mathematics for Humans <https://home.sandiego.edu/~shulman/

> humans.html <https://home.sandiego.edu/~shulman/humans.html>>

> > University of San Diego
> >
> > "The role of the intellectual cannot be to excuse the violence of one
> > side and condemn that of the other."
> >          -- Albert Camus
> >
> > --
> > You received this message because you are subscribed to the Google Groups
> > "PreTeXt support" group.
> > To unsubscribe from this group and stop receiving emails from it, send an
> email
> > to pretext-suppo...@googlegroups.com <mailto:pretext-

> support%2Bunsu...@googlegroups.com> <mailto:pretext- <mailto:pretext->
> > support+u...@googlegroups.com
> <mailto:support%2Bunsu...@googlegroups.com>>.
> > To view this discussion visit https://groups.google.com/d/msgid/pretext-

> support/ <https://groups.google.com/d/msgid/pretext-support/>
> >
> CADYavpxHM8z%3Dme_Mu%3D%2BtogimudVihvhC8%3D_aoWN_kKH2pNtaOw%40mail.gmail.com
> <http://40mail.gmail.com>
> > <https://groups.google.com/d/msgid/pretext-support/ <https://
> groups.google.com/d/msgid/pretext-support/>
> >
> CADYavpxHM8z%3Dme_Mu%3D%2BtogimudVihvhC8%3D_aoWN_kKH2pNtaOw%40mail.gmail.com
> <http://40mail.gmail.com>?

> > utm_medium=email&utm_source=footer>.
>
> --
> You received this message because you are subscribed to a topic in the
> Google Groups "PreTeXt support" group.
> To unsubscribe from this topic, visit https://groups.google.com/d/topic/
> pretext-support/ts2Xcbkyj9k/unsubscribe <https://groups.google.com/d/topic/
> pretext-support/ts2Xcbkyj9k/unsubscribe>.
> To unsubscribe from this group and all its topics, send an email to pretext-
> support+u...@googlegroups.com <mailto:pretext-
> support%2Bunsu...@googlegroups.com>.
> To view this discussion visit https://groups.google.com/d/msgid/pretext-

> support/MTAwMDAxNy5iZWV6ZXI.1768069736%40pnsh <https://groups.google.com/d/
> msgid/pretext-support/MTAwMDAxNy5iZWV6ZXI.1768069736%40pnsh>.

>
>
>
> --
> Michael Shulman
> Professor of Mathematics for Humans <https://home.sandiego.edu/~shulman/humans.html>
> University of San Diego
>
> "The role of the intellectual cannot be to excuse the violence of one
> side and condemn that of the other."
>         -- Albert Camus
>
> --
> You received this message because you are subscribed to the Google Groups
> "PreTeXt support" group.
> To unsubscribe from this group and stop receiving emails from it, send an email
> to pretext-suppo...@googlegroups.com <mailto:pretext-
> support+u...@googlegroups.com>.
> To view this discussion visit https://groups.google.com/d/msgid/pretext-support/

> CADYavpzcC2sG5VxLAehPq2WrwkZHYv%3Dh2a5ALGJMqdsyCuemZQ%40mail.gmail.com <https://
> groups.google.com/d/msgid/pretext-support/
> CADYavpzcC2sG5VxLAehPq2WrwkZHYv%3Dh2a5ALGJMqdsyCuemZQ%40mail.gmail.com?
> utm_medium=email&utm_source=footer>.

[Michael Shulman]

Thanks!

Why do you say nested cases environments would be too much?  Since PreTeXt currently has no other way to produce the effect of a {cases} environment, it doesn't seem to me that {cases} should be deprecated.  Do you just mean that it would be too much work to detect nested cases and they're likely to be rare?

Another case of an ugly period that I just noticed is {multlined}.  I don't think PreTeXt has any other way to produce this effect either, does it?

(Side note: the link to "Supported LaTeX commands" at https://pretextbook.org/doc/guide/html/overview-math.html is broken.)

To unsubscribe from this topic, visit https://groups.google.com/d/topic/pretext-support/ts2Xcbkyj9k/unsubscribe.
To unsubscribe from this group and all its topics, send an email to pretext-suppo...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/pretext-support/MTAwMDAwMC5iZWV6ZXI.1768163234%40pnsh.

--

Michael Shulman

Professor of Mathematics for Humans

[David W. Farmer]

Not speaking for what Rob meant, but to me nested cases fails the
"common and reasonable" test.

That is, "what is common and reasonable should be easy" is one of
the PreTeXt principles. I don't think nested cases is common:
I don't recall seeing it and certainly have never done it myself.

As to whether it is reasonable, I personally cannot think of when
I might use it. Not sure if I mean that as an invitation
for examples :).

Regards,

David

> To unsubscribe from this group and stop receiving emails from it, send an email to pretext-suppo...@googlegroups.com.

> To view this discussion visit

> https://groups.google.com/d/msgid/pretext-support/CADYavpy8YJ2s0y5BV_9CULBPRxsdwYL99RR57QPDPWiiM63Z9A%40mail.gmail.com.
>
>

[Michael Shulman]

Well, "PreTeXt makes it easy for authors to implement features which are both common and reasonable" isn't quite the same as "PreTeXt doesn't make it possible for authors to implement features that are either uncommon or unreasonable."  I doubt I've ever used nested cases or ever will, but I could imagine a situation in which I might (although I'll forbear from supplying an example).

More convincingly, though, I think a {multlined} inside a {cases} is eminently reasonable.  And if you were going to implement that, probably it wouldn't be any more work to support nested cases too.

To view this discussion visit https://groups.google.com/d/msgid/pretext-support/76b2c449-5f0-4a39-a141-ff648d89bd87%40aimath.org.