Re: Pringsheim Notation for continued fractions

Thanks to everyone for helping, 

I will go with Florent’s solution. I made a cosmetic change by adjusting the rule thickness to match the fraction bar thickness.
This seems to depend on the font — is there a variable I can access, or do I just do it on a case-by-case basis?

Matthias

> On Jun 15, 2026, at 7:54 AM, Bruce Horrocks <[email protected]> wrote:
> 
> 
> 
>> On 14 Jun 2026, at 17:18, Matthias Weber <[email protected]> wrote:
>> 
>> Dear All, 
>> 
>> 
>> I would like to typeset continued fractions as attempted and failed in the second line of the following MWE:
>> 
>> \def\cFrac#1#2{%
>> \vcenter{\hbox{\strut$#1$\,\vrule}\hrule\hbox{\strut\vrule\,$#2$}}}
>> 
>> \starttext
>> \startformula
>> \startalign
>> \NC  a_0+a_0a_1+a_0 a_1 a_2+a_0 a_1 a_2 a_3 \NC  = \cfrac{a_0}{1-\cfrac{a_1}{1+a_1-\cfrac{a_2}{1+a_2-\cfrac{a_2}{1+a_2-\cfrac{a_3}{1+a_3-\cdots}}}}}\NR
>> %\NC   \NC  = \frac{a_0|}{|1}-\frac{a_1|}{|1+a_1}-\frac{a_2|}{|1+a_2}-\frac{a_3|}{|1+a_3}-\cdots\NR
>> \NC   \NC  = \cFrac{a_0}{1}-\cFrac{a_1}{1+a_1}-\cFrac{a_2}{1+a_2}-\cFrac{a_3}{1+a_3}-\cdots\NR
>> \stopalign
>> 
>> \stopformula
>> \stoptext
>> 
>> 
>> The macro is from 
>> 
>> https://tex.stackexchange.com/questions/68190/how-do-i-typeset-continued-fractions-in-pringsheims-concise-notation
>> 
>> where this question is discussed for LaTeX.
>> 
>> Unfortunately, the vertical bars on the top of the fractions do not align with the right end of the fraction bar.
>> 
>> 
>> Any suggestions?
> 
> It can be hacked using a mathmatrix and the (under-documented) \GL command. It puts quite a lot of horizontal space in though because of the need to use empty \NC columns and I don't know a way to force them to be narrower, so maybe Florent's solution is better for you?
> 
> \def\cFrac#1#2{%
> \vcenter{\hbox{\strut$#1$\,\vrule}\hrule\hbox{\strut\vrule\,$#2$}}}
> 
> \starttext
> \startformula
> \startalign
> \NC  a_0+a_0a_1+a_0 a_1 a_2+a_0 a_1 a_2 a_3 \NC  = \cfrac{a_0}{1-\cfrac{a_1}{1+a_1-\cfrac{a_2}{1+a_2-\cfrac{a_2}{1+a_2-\cfrac{a_3}{1+a_3-\cdots}}}}}\NR
> %\NC   \NC  = \frac{a_0|}{|1}-\frac{a_1|}{|1+a_1}-\frac{a_2|}{|1+a_2}-\frac{a_3|}{|1+a_3}-\cdots\NR
> \NC   \NC  = \cFrac{a_0}{1}-\cFrac{a_1}{1+a_1}-\cFrac{a_2}{1+a_2}-\cFrac{a_3}{1+a_3}-\cdots\NR
> \stopalign
> \stopformula
> 
> 
> Alternate:
> 
> \starttexdefinition PCN #1 #2
>  \startmathmatrix
>    \NC \GL[1][d]             \NC #1 \NC \GL[1][d,c]\GL[2][d]\GL[2][t,c]  \NC\NR
>    \NC \GL[3][t]\GL[3][d,c]  \NC #2 \NC                                  \NC\NR
>  \stopmathmatrix
> \stoptexdefinition
> 
> 
> \startformula
> a = \PCN{a_0}{1} - \PCN{a_1}{1+a_1} - \PCN{a_2}{1+a_2} - \PCN{a_3}{1+a_3} - \cdots
> \stopformula
> \stoptext
> 
> 
> Regards,
> —
> Bruce Horrocks
> Hampshire, UK
> 
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