Help talk:Displaying a formula

Writing chem ionic equation

How do I write:

Fe²⁺ + Cu²⁺

using <chem>? I cannot figure out how to get the "+" between the pair of ions to render correctly. Here are my attempts at the left-hand side:

<chem>Fe2+ + Cu2+</chem>	${\ce {Fe2+ + Cu2+}}$
<chem>Fe+2 + Cu+2</chem>	${\ce {Fe+2 + Cu+2}}$
<chem>Fe^{2+} + Cu^{2+}</chem>	${\ce {Fe^{2+}+ Cu^{2+}}}$
<chem>Fe^{+2} + Cu^{+2}</chem>	${\ce {Fe^{+2}+ Cu^{+2}}}$

DMacks (talk) 20:09, 20 January 2018 (UTC)

<chem>Fe^2+ + Cu^2+</chem> seems to work ${\ce {Fe^2+ + Cu^2+}}$. --Salix alba (talk): 20:17, 20 January 2018 (UTC)

Thanks! DMacks (talk) 02:28, 24 January 2018 (UTC)

Migration away from old texvc <math> engine

There is now a project to migrate away from the texvc renderer for <math> expressions. This was the default a few years ago which produces PNG images, now we have a hybrid solution with uses MathJax in the backend to produce svg images and sometimes xml. There is still some legacy from texvc as it is used in the frist parsing step of the current engine. This means there are some idiosyncrasies in the syntax which differ from standard LaTex:

Current syntax	Suggested replacement	Comment
$	\$	redefinition would involve changing the character code
%	\%	redefinition would involve changing the character code
\and	\land	causes normal align environment to fail
\or	\lor	see [1]; causes teubner to fail
\part	\partial	acceptable if the document doesn't use sectioning with \part.
\ang	\angle	this only conflicts with siunitx package.
\C	\Complex	conflicts with puenc.def e.g. from hyperref package
\H	\mathbb{H}	conflicts with text command \H{0} which is ő.
\bold	\mathbf
\Bbb	\mathbb
\pagecolor	remove	not needed and not working anymore, done on en-wiki mainspace
<ce>...</ce>	<chem>...</chem>	Chemistry environment, done on en-wiki mainspace

The first step in the project will involve deprecating the old syntax and running a bot or semi-automated edits to change the syntax. These should not result in any visible change to the pages. The bot doing the work is User:Texvc2LaTeXBot which is currently seeking approval. Changes will also be made to the Visual Editor to produce the new syntax.

Subsequent stages in the project are discussed at mw:Extension:Math/Roadmap, these involve some more complex problems with the <chem> syntax. Eventually the texvc part will be removed completely and there may be some slight change to the rendered output. The main discussion of the project happens at T195861 and your input is welcome. Discussion on the English wikipedia should be on WT:WPM--Salix alba (talk): 15:55, 22 June 2018 (UTC)

dash instead of minus sign produced by math tag

See minus sign and 5 − 3 = 2 versus $5-3=2$. It also produces text that is too small. --Espoo (talk) 16:24, 9 November 2018 (UTC)

@Espoo: (I fixed the weird horrible error; it was from a badly placed tag in the previous section header). I don't understand what you're referring to though. What's too small? What are we supposed to be seeing at minus sign? –Deacon Vorbis (carbon • videos) 16:33, 9 November 2018 (UTC)

Thanks! The text "5 - 3 = 2" is too small in the second example, and its minus sign is much too long. --Espoo (talk) 16:38, 9 November 2018 (UTC)

It looks fine to me. It could be related to your math display settings. Look under Preferences → Appearance → Math, and see if changing to "PNG images" helps. Does any other rendered math look weird? If that doesn't help, can you post a screenshot of how it appears to you? –Deacon Vorbis (carbon • videos) 16:43, 9 November 2018 (UTC)

That's very weird because the minus sign looks like a dash (even with png now), which is easily misread as "from a to b", on both my android smartphone and windows PC. I'll attach screenshots soon and would be grateful for your screenshot too. --Espoo (talk) 16:55, 9 November 2018 (UTC)

Some issues

\mathbf, \mathit and \mathsf do not work on Greek letters that are defined as a Latin letter in roman type, e.g., \mathit\Alpha (${\mathit {\mathrm {A} }}$) is displayed as an upright letter. While \mbox{a} and \text{a} do work, \mbox a and \text a do not. Support for upright Greek small letters seems to be missing in general, though at least \text{µ} (using U+00B5 rather than U+03BC) works: ${\text{µ}}$. \omicron ($\mathrm {o}$ – should be italic!) and \varcoppa ($\mbox{\coppa}$) are displayed wrongly.

Also note that \oiint ($\oiint$), \oiiint ($\oiiint$ – another try: $\oiiint \ \$) and $\varointclockwise$ are displayed with an upright integral symbol while, e.g., \int ($\int$) and \oint ($\oint$) are not. It would be great to have both variants (upright, slanted); the upright version fits to the practice of writing $\mathrm {d} x$ (→ ISO 80000-2:2009) instead of $dx$. -- IvanP (talk) 15:18, 4 April 2019 (UTC)

RfC on <chem>

What is <chem>: a recommended device or an obscure hack?

See also: § Writing chem ionic equation

• Should opinions of the “chemical” community in en.Wikipedia on <chem>...</chem> be mentioned here? I’m sure it is an important guidance for a help page in the English Wikipedia. The user Deacon Vorbis wages an edit war over it. Incnis Mrsi (talk) 16:24, 7 August 2019 (UTC)

Funny how it's always only the other person waging the edit war and never oneself. In any case, if something needs to be updated here in order to reflect common practice, that's fine. Your first two additions were completely inappropriate talking about edit warring and aspersions. Since you used an undo, I missed that the third had changed wording. But there's still a problem that you're basing a fairly substantial change off of something that one person said in response to an incomprehensible post on the chemistry wikiproject talk page. Without wider input, it's hard to know what to even make of it. So again, if something needs to be updated here, then you should coordinate with people who maintain chem articles and make sure what current practice really is. –Deacon Vorbis (carbon • videos) 16:54, 7 August 2019 (UTC)

Even so, there is also a concern I have about WP:CONLEVEL. --Izno (talk) 14:22, 10 August 2019 (UTC)

Can Izno please speak more specifically and less elitistic? Proponents of <chem> may come here and there and argue against me and Graeme. But the use of <chem> is controversial – this is currently a reality of en.Wikipedia which has to be documented. Incnis Mrsi (talk) 14:36, 10 August 2019 (UTC)

By the way, we see the RfC sabotaged by Deacon_Vorbis while the same Deacon_Vorbis vocally calls for “coordination with people who maintain chem articles”. Incnis Mrsi (talk) 14:50, 10 August 2019 (UTC)

Anyway the edit by Deacon_Vorbis indicates that there should be a discussion before, so that at least the scope and options for the RFC can be determined. I have a few issues with <chem>. Firstly issues for our readers, that it cannot be copied and pasted cleanly from a screen. There is a heap of extra text attached to the copy. Similarly searching on a page or on the Wikipedia search box may not find the formula due to extraneous inclusions. The third issue is for our editors who need to learn a lot before being able to use the <chem> tag properly. There are also the chem and chem2 templates which may have similar problems or reduced problems. I normally use sub and sup tags, and I sometimes use a template that merges them together. One feature that I dont know how to get is a line over the top that joins to a symbol at each end in order to illustrate a ring closure in a linear formula. Graeme Bartlett (talk) 12:58, 11 August 2019 (UTC)

@Graeme Bartlett: I defer to any solution by the “chemical community” which will deter wrecking and censorship. Specific formulation for preferences for <chem> and the templates are not of great importance. Incnis Mrsi (talk) 13:11, 11 August 2019 (UTC)

This statement is indicating drama and interpersonal problems. I will note that Deacon Vorbis removed your statement about yourself. If people are misbehaving and cannot be resolved by a civil discussion then there is a special drama board: WP:AN/I. So lets have a discussion of the use of the chem tag, and how it should be described on this help page first. In this discussion just discuss the topic and not the users. That will avoid stepping into the next level. It seems that this section has already upset two people. Graeme Bartlett (talk) 22:27, 11 August 2019 (UTC)

Again, there may be discussions on <chem> and arguments in defence of it at least for certain special applications. But its shortages indicate that—in conditions where {{chem2}} performs well—the current implementation of <chem> is controversial at best and detrimental at worst. Not all help-page readers are expected to understand what exactly means controversial, hence it would be better to suggest: to avoid trouble, don’t push <chem> boldly. Incnis Mrsi (talk) 22:36, 11 August 2019 (UTC)