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Weird examples of limits on Help:Displaying_a_formula
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Description

The page

https://en.wikipedia.org/wiki/Help:Displaying_a_formula#Subscripts.2C_superscripts.2C_integrals

contains the following example:

\frac{\sum\limits^{^N}_{k=1} k^2}{a}
\bigcap_{i=_1}^n E_i
\bigcup_{i=_1}^n E_i

Where "N" and "1" are used as sub/sup scripts. I'm not sure what's the intention here, but the rendering does not look good to me and that obviously confuse assistive technologies.

Event Timeline

fredw created this task.Jul 9 2015, 12:13 PM
fredw raised the priority of this task from to Needs Triage.
fredw updated the task description. (Show Details)
fredw added projects: Math, Mathoid, Accessibility.
fredw added a subscriber: fredw.
Restricted Application added a subscriber: Aklapper. · View Herald TranscriptJul 9 2015, 12:13 PM
Physikerwelt triaged this task as Low priority.Jul 19 2015, 11:26 PM
Physikerwelt set Security to None.

I classified the task as low since the output is somehow like I would the TeX input expect to look like

From viewing the examples, all I notice is that in the lower limit, "i=1", the terms on the two sides of the equal sign are at different levels. I'm guessing that is the problem seen by fredw with \bigcap and \bigcup.

fredw added a comment.Jul 22 2015, 2:29 PM

Does anyone know about this special notation for limits? This looks a TeX hack to achieve a purely visual distinction for "alternative limits style".

In my opinion, it is not really semantically correct to write the right operand as a subscript. For example, one could define two equalities $=_1$ and $=_2$ (say from the ideals of meager and null sets of reals) and then write $f =_1 g$ and $f =_2 g$ and here "g" is the right operand not 1/2.

Assistive technologies will present this as "i equal subscript 1" which also sounds a bit weird.

Maybe this bug is just "invalid" and we do not have a proper solution for now. But this is one of the painful LaTeX hacks that do not work well when one tries to think further than just "math on paper"... I wonder if we really want to keep that suggestion on the Help:Displaying_a_formula page.

Pkra added a subscriber: Pkra.Dec 5 2018, 3:03 PM

Is there an actionable issue here?

The example in the help page has changed which seems to indicate that this was a typo.

The current rendering for the examples in the OP look fine (and match real TeX output); the update version also looks fine.

Pkra closed this task as Invalid.Dec 7 2018, 11:29 AM