Re: Missing \dddot and \ddddot

[Hans Hagen <pragma@wxs.nl>]

Aditya Mahajan wrote:
> On Thu, 14 Sep 2006, Hans Hagen wrote:
>
>   
>> Aditya Mahajan wrote:
>>     
>>> On Thu, 14 Sep 2006, WN wrote:
>>>
>>>
>>>       
>>>> Hello,
>>>> I need to use \dddot and \ddddot in one of my documents, does anyone
>>>> know how to
>>>> define these math symbols.
>>>>
>>>>         
>>> The trouble is that most fonts do not contain these accents.
>>> amsmath.sty gets over this definition by faking these symbols. It is
>>> easy to port these definitions to context.
>>>
>>> amsmath.sty definition
>>>
>>> \newcommand{\dddot}[1]{%
>>>    {\mathop{#1}\limits^{\vbox to-1.4\ex@{\kern-\tw@\ex@
>>>     \hbox{\normalfont ...}\vss}}}}
>>> \newcommand{\ddddot}[1]{%
>>>    {\mathop{#1}\limits^{\vbox to-1.4\ex@{\kern-\tw@\ex@
>>>     \hbox{\normalfont....}\vss}}}}
>>>
>>>
>>> Converting to context
>>>
>>> %--------------------%<------------------------------------
>>> \unprotect
>>>
>>> % The true copy of amsmath definitions
>>> \def\amsdddot {\limits^{\vbox to -1.4ex{\kern-2ex\hbox{\the\textfont\z@ ...}\vss}}}
>>> \def\amsddddot{\limits^{\vbox to -1.4ex{\kern-2ex\hbox{\the\textfont\z@....}\vss}}}
>>>
>>> % I do not understand why you need to give negative height
>>>
>>>       
>> \setbox\scratchbox{..} \ht\scratchbox0pt \dp\scratchbox-2pt
>>     
>
> I was wondering why amstex definition does this, as the 1.4ex depth 
> was too big. Then I realized that it is not 1.4ex but 1.4\ex@ with 
> \ex@ as .2326ex. ughh....the ugly syntax of plain tex...
>
> So here is a more reliable reproduction of amstex dddot and ddddot
>
> \newdimen\amstexex
>
> \amstexex = .2326ex
>   
what's this funny number based on, somehow related to interlinespace?

one cannot define a measure globally this way, since an ex is font 
dependent,;

\def\amstexex{\dimexpr.08\lineheight\relax}

or so may be better
> \def\dotsadjustbox#1%
>    {\vbox to -1.4\amstexex{\kern-2\amstexex
>     \hbox{\the\textfont\zerocount#1}\vss}}
>
> \def\dddot#1%
>    {{\mathop{#1}\limits^{\dotsadjustbox{...}}}}
>
> \def\ddddot#1%
>    {{\mathop{#1}\limits^{\dotsadjustbox{....}}}}
>
> \starttext
> $\dddot{a}_{\dddot{b}}$
>
> $\ddddot{a}_{\ddddot{b}}$
> \stoptext
>
> Hans, can these definitions be added to the core?
>
> Aditya
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>   


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