# [luatex] "Proper" use of \Udelimiterover &c

Will Robertson wspr81 at gmail.com
Wed Jul 14 09:34:09 CEST 2010

```Hi Taco,

On 14/07/2010, at 4:53 PM, Taco Hoekwater wrote:

>> Would it make sense to treat a \Udelimiterover construction as an
>> operator with limits automatically? E.g., I expected
>>
>> {\Udelimiterover "4 "23DE {a+b}}^{d+e}
>>
>> to do the "right thing", but looking at it this way perhaps it's
>> impossible to do this with this construction of maths primitives? (Sorry
>> I'm not entirely up to speed on the internals of the maths engine.)
>
> When I implemented this, I did not realise that this would make sense.
> Is such a construct as this *always* a large operator?

Well, the idea is that you either use the overbrace "naked" and it doesn't matter about the operator stuff, or you give it an attached piece of math as in this example.

So the Plain definition of \overbrace is

\mathop{\vbox{[...snip!...]}}\limits

so that you can place material directly on top.