[NTG-context] "Invalid field" in Mark IV

[Taco Hoekwater]

Aditya Mahajan wrote:
> On Wed, 13 May 2009, Flavien Lambert wrote:
> 
>> In the following example, it is the ";" that leads to the error
>> \def\vect#1{%
>>  \overrightarrow{#1}
>> }
>> \starttext
>> $({\rm O};\vect{e_{x}})$
>> \stoptext
>>
>> If you suppress it, it works fine. (???)
> 
> Taco, the error also occurs with cambria. So, by your definition, it is 
> an engine error.

It isn't, it is caused by the lua postprocessing of math lists that
does not deal with choice nodes properly. Hans should fix the lua
code, but meanwhile I do have an 'almost' engine-level solution:

   \def\mathchoice#1#2#3#4%
     {\ifcase\mathstyle#1\or#1\or#2\or#2\or#3\or#3\or#4\or\#4\fi}


Best wishes,
Taco