# [lltx] $n\choose k$-issue with OpenType math fonts

Ulrik Vieth ulrik.vieth at arcor.de
Sat Mar 5 20:57:06 CET 2011

On 03/05/2011 03:58 PM, Philipp Stephani wrote:

> There surely exists a reason why Microsoft chose to leave out the three
> parameters delim1, delim2, and sub2.
>Perhaps they thought that distinguishing between \left(1 \atop 2\right)
> and 1 \atopwithdelims() 2 would be too surprising and seldom relevant.
> I think better than guessing correct parameter values would be
> to do the  equivalent of \left(1 \atop 2\right) if the user requested
> 1 \atopwithdelims() 2 and the parameters are undefined.

I already discussed this issue in my paper "OpenType Math illuminated"
http://www.tug.org/TUGboat/tb30-1/tb94vieth.pdf on p.28.

I essentially came to the same conclusions:

"In the absence of a better solution, it may be
best to simply avoid using \atopwithdelims with
OpenType math fonts in the new TEX engines and
to redefine user-level macros (such as \choose)
in terms of \left and \right delimiters."

Regards, Ulrik.