Hello,
I also use a square to complete a demonstration. I tried this without
success
Thank you
Fabrice

\definesymbol[Fin][\mathematics{\square}]
\def\qed{\strut\wordright{\symbol[Fin]}}

\defineenumeration
  [proof]
  [text=Démonstration,
   alternative=serried,
   distance=\zeropoint,
   number=no,
   headstyle=boldslanted,
   width=broad,
   closesymbol={\symbol[\qed]}]

\starttext
\startproof
\startformula
a^2 + b^2 = c^2
\stopformula
\stopproof
\stoptext


Le mar. 4 août 2020 à 14:02, Otared Kavian <otared@gmail.com> a écrit :

> Hi Hans,
>
> Thanks for the hint which consists in adding an \ifmmode to the definition
> of \qed.
> However, as you suggest, one needs some other mechanism in math mode,
> since with your new definition of \qed the alignment of the formula changes
> when one adds this close symbol:
>
> %%%% begin-example-qed.tex
> \definesymbol[Fin][\mathematics{\square}]
> \def\qed{\ifmmode\quad\symbol[Fin]\else\strut\wordright{\symbol[Fin]}\fi}
> \starttext
> \startformula
> a^2 + b^2 = c^2.
> \stopformula
> \startformula
> a^2 + b^2 = c^2. \qed
> \stopformula
> One sees that\type{\qed} in the formula changes the alignment of the
> formula. \qed
> \stoptext
> %%%% end-example-qed.tex
>
> Thanks a lot for everything: Otared
>
> > On 4 Aug 2020, at 13:24, Hans Hagen <j.hagen@xs4all.nl> wrote:
> >
> > On 8/4/2020 11:17 AM, Otared Kavian wrote:
> >> Thanks Hans for your explanations.
> >> The problem I encountered is that, the command \qed is used dozens of
> time in my text without any issue because it was preceded by something on
> th eline, but the only place where it was alone after a formula resulted in
> the error and it was not easy for me to isolate the issue…
> >> By the way, in mkii it was possible to add \qed on the last line of a
> math formula, but that does not work anymore:
> >> \definesymbol[Fin][\mathematics{\square}]
> >> \def\qed{\strut\wordright{\symbol[Fin]}}
> >> \starttext
> >> \startformula
> >> a^2 + b^2 = c^2. \qed
> >> \stopformula
> >> The above formula does not show the close symbol.\qed
> >> \stoptext
> >> Is there a way to have something like \qed work in math formulas?
> > because that's now hwpo wordright works ...
> >
> > \def\qed{\ifmmode\quad\symbol[Fin]\else\strut\wordright{\symbol[Fin]}\fi}
> >
> > but we probably need something different, something that hooks into
> display math
> >
> > 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
> > -----------------------------------------------------------------
>
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