[XeTeX] additional beginL endL nodes in math

[Khaled Hosny]

On Wed, Apr 15, 2015 at 09:19:04PM +0100, Philip Taylor wrote:
> 
> 
> Khaled Hosny wrote:
> 
> > On Wed, Apr 15, 2015 at 08:52:38PM +0100, Philip Taylor wrote:
> 
> >> Might it not be possible to resolve this by making the new behaviour
> >> optional, using a new primitive for the purpose ?
> > 
> > So this just penalizes the unlucky people who need to enable the special
> > behaviour, I’d rather penalize everyone and have a consistent, if
> > erratic in someways, behaviour.
> 
> I do not understand.  If system A performed function Y until now, yet
> its designer/maintainer wishes it to perform function Y' henceforth, how
> can those who wish to exploit Y' be /penalised/ by being asked to invoke
> the operation specifically, rather than have it just happen and destroy
> backwards compatibility ?  I see no "penalty" at all, just allowing the
> informed user to make an explicit choice between the two behaviours.

It is not possible (not with a reasonable effort anyway) to support both
behaviours, so the option would boil down to having right-to-left
“extension” enabled or not.

Regards,
Khaled