[luatex] How to get a \mid binary relation that grows in LuaTeX

[Hans Hagen]

On 11/15/2017 7:32 PM, Hans Hagen wrote:
> On 11/15/2017 6:44 PM, David Carlisle wrote:
>> Hans wrote
>>
>>> sure but then, using an empty \mathrel{} in there is kind of bad
>>
>> It's possibly the only way in classic etex to define a version of
>> \middle that gives \mathrel space
>>
>> \def\relmiddle#1{\mathrel{}\middle#1\mathrel{}} ... \rmiddle | ...
>>
>> acts like a relation with respect to automatic muskips on both sides
>>
>>
>>> .. better add some explicit muskip then
>>
>> you can't classically detect what \muskip needs adding unfortunately...
>>
>>
>> so \Umiddle is (of course:-) a whole lot better (apart from the
>> confusing numbering scheme:-) but
>> the \mathrel{}\middle|\mathrel{} idiom is likely to be quite common in
>> legacy documents moving to luatex
> i will have a look at remapping these extended classes (after all we 
> don't have more spacing parameters)
the next version will use the normal class numbers

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