Re: math align

[Hans Hagen <pragma@wxs.nl>]

David Arnold wrote:

> Hans, Willi, et al,
>
> I was thinking there are pros and cons to each solution, Hans' and  
> Willi's. So I tried:
>
> Here are some simple examples of adding fractions already having  
> common denominators.
>
> %output=pdf
>
> \input math-ext
>
> \starttext
>
> \placeformula[-]
> \startformula
>   \startalign[m=2,distance=5em]
>     \frac5{21}-\frac3{21}&=\frac{5-3}{21} &
>     \frac{2}{x+2}-\frac{x-3}{x+2}&=\frac{2-(x-3)}{x+2}\\
>     &=\frac2{21} & &=\frac{2-x+3}{x+2}\\
>     &&&=\frac{5-x}{x+2}
>   \stopalign
> \stopformula
>
> \startbuffer[1]
> \framed[frame=on,width=fit]
>    {\startformula
>      \eqalign{
>        \frac{5}{21}-\frac{3}{21}
>        &=\frac{5-3}{21}\cr
>        &=\frac{2}{21}}
>    \stopformula}
> \stopbuffer
>
> \startbuffer[2]
>   \framed[frame=on,width=fit]
>   {\startformula
>     \eqalign{
>       \frac2{x+2}-\frac{x-3}{x+2}
>       &=\frac{2-(x-3)}{x+2}\cr
>       &=\frac{2-x+3}{x+2}\cr
>       &=\frac{5-x}{x+2}}
>   \stopformula}
> \stopbuffer
>
> \startbuffer
>   \startcombination[2*1]
>     {\externalfigure[1][width=0.45\textwidth,type=buffer]}{}
>     {\externalfigure[2][width=0.45\textwidth,type=buffer]}{}
>   \stopcombination
> \stopbuffer
>
> \placefigure
> [][-]
> {none}
> {\getbuffer}
>
> \stoptext
>
> As you can see, Hans' solution works perfectly, but note the very  
> ugly source code for that section. Willi's source is cleaner, much  
> easier to read (especially at a later date when I will have to  
> revisit for revisions), but it doesn't work (the output is scaled of  
> course).
>
> Any suggestions as to how I can fix Willi's approach so it doesn't  
> scale?


wikiable:

\definecombination[twoformulas][location=top,align=middle]

\startalignment[middle] \dontleavehmode \startcombination[twoformulas][2*1]
    {\getbuffer[1]} {}
    {\getbuffer[2]} {}
\stopcombination \stopalignment

\def\StartTwo{\startalignment[middle] \dontleavehmode 
\startcombination[twoformulas][2*1]}
\def\StopTwo {\stopcombination \stopalignment}]

\StartTwo
  {\getbuffer[1]} {}
  {\getbuffer[2]} {}
\StopTwo

\StartTwo
  {\getbuffer[1]} {correct}
  {\getbuffer[2]} {wrong}
\StopTwo