On 11/13/2020 4:21 PM, Jean-Philippe Rey wrote:
Dear list,
I am trying to switch from MKIV to LMTX. I've just found a discrepancy with the
following code which puts space between two lines in a math alignment. This
minimum breaking example uses \startcases, but the same problem arises with
other alignment macros.
\starttext
\startformula
\startcases
\NC 1 \NC if not null \NR
\noalign{\vskip2ex}
\NC 0 \NC if null \NR
\stopcases
\stopformula
\stoptext
This snippet works fine with MKIV but breaks in LMTX (see attached log file).
Is this a bug in LMTX or is there another way to insert space between two lines?
I've already tried different other solutions, but none seems really appropriate:
- \intertext produces a vertical space of at least 3 lines and I haven't been
able to make it smaller;
- adding an empty line (\NC \NR) produces a smaller space but I am unable to
reduce its height below a minimum value (roughly a line);
- adding a \vrule to the above or below line works fine but it needs some
calculation depending on the content of the line.
we're in the process of upgrading some code in lmtx ... so the next
upload will provide \TB (as in other tabular like mechanisms)
Actually your code will not work in a recent lmtx. This has to do with
the fact that a \noalign is always somewhat tricky (relates to the
engine looking ahead for specific commands). In mkiv (an dolder lmtx)
there is some \noalign overload magic that deals with that but in recent
lmtx we use a different approach.
\starttext
The next code defines a macro \TB that is protected but still acceptable
for alignment lookahead checking with an optional argument and that
behaves like \blank.
\pushoverloadmode
\noaligned\tolerant\protected\def\TB[#1]{\noalign{\blank[#1]}}
\popoverloadmode
\startformula
\startcases
\NC 1 \NC if not null \NR
\TB[2ex]
\NC 0 \NC if null \NR
\TB[4*big]
\NC 0 \NC if null \NR
\stopcases
\stopformula
\stoptext
(There is a little more involved because we want to protect commands
like \TB against overloading while at the same time we do overload them
in all those different table mechanisms but this is not something users
have to worry about.)
Btw, using \noalign is to be avoided because it assumes that the
mechanism uses the alignment mechanism.
But best wait for the next upload.
Hans
-----------------------------------------------------------------
Hans Hagen | PRAGMA ADE
Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the
Wiki!
maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage : http://www.pragma-ade.nl / http://context.aanhet.net
archive : https://bitbucket.org/phg/context-mirror/commits/
wiki : http://contextgarden.net
___________________________________________________________________________________
