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Martin Sleziak
Martin Sleziak
5:27 AM

Problems in posts and comments added by automated adding of begingroup .. endgroup

21 hours ago, 15 hours 27 minutes total – 49 messages, 3 users, 1 star

Bookmarked 22 mins ago by Martin Sleziak

There was a recent change - all comments and posts are surrounded by \begingroup..\endgroup. math.meta.stackexchange.com/questions/4130/…
13
A: The scope of \newcommand is the entire page

Adam LearIt pains me to break this thread by fixing the issue, but here we are. :) We are now inserting \begingroup and \endgroup directives into post and comment bodies, so all command definitions should be scoped to individual posts. For now, I'm only enabling this on Math (and here on meta), but barr...

This can sometimes cause problems. For example, if a comment relied on macro defined in another answer, then the comment is now not rendered correctly.
Similar situation arises if a post relies on a macro defined in another post. (Typically an answer might use macro from the question.)
Of course, such posts (answers) can be edited manually - the only possible problem is not to flood the frontpage with too many posts edited.
Comments can only be edited by mods. Even there we can have a possible problem - it's possible that after expansion the comment will no longer fit the character limit.
in Math Meta Chat, 6 hours ago, by quid
@MartinSleziak I'd say flag for mods. We sometimes get such flags. If people do that as they stumble over it, it could be mangable.
And, of course, it would be not good if mods were flooded by many flags about this problem. (This will not arise if people flag them as they stumble upon them. It might be a problem if people search for such posts systematically.)
There might be some SEDE queries, which might help with finding such posts and comments. I will try to post here some such queries. I will mark the messages with SEDE queries by data-explorer to make them easier to find.
It might help to come up with some list of commonly used macro names. For messages with specific searches (be it using SEDE or using the built-in search) I will user search - such messages can be found in the same way.
And possibly I will include here links to specific examples to posts/comments - in cases where I do not want to edit them right away because there have been already too many questions bumped. (Similarly, there might be situations where it is to postpone flag for later...?)
Here are some queries I was able to come with which might be useful:
data-explorer Posts containing a given text, for example \lcm
data-explorer Posts between two dates containing a given text, for example \lcm since 2018
Probably it might be more useful to search for those where no macro is defined.
data-explorer Posts containing a given text with no macro definition, for example \lcm
data-explorer Posts containing string1 but not string2, for example \lcm but not \newcommand{\lcm}
And we can do similar stuff with comments
data-explorer Comments containing a given string, such as \lcm
data-explorer Comments with a given string within a date range, such as \lcm since 2018
And again, we might try to avoid those which contain a macro definition
data-explorer Comments containing a given string with no macro definition, example with \lcm
data-explorer Comments containing string1 but not string2, such as \lcm but not \newcommand{lcm}
Here are some examples of what I meant by specific searches:
search comments Some commonly used names for macros are \lcm, \rank.
search posts Some commonly used names for macros are \lcm, \rank.
As I've mentioned you can easily locate such messages in the transcript. You can search also for messages tagged with (posts) or tagged with (comments).
search Of course, one can also use built-in search to find some stuff, for example \newcommand. But it will not distinguish between \rank and rank - to search for such posts you'll need SEDE.
I see that in the above message I have exchanged posts and comments by mistake - here is a correction.
Here is an example of a "broken" comment which uses two macros:
Let $M$ be any $R$-module and $I$ an ideal. Then for each element $m\in M$, there is an $R$-linear map $g_m: I \rightarrow M$ given by $g_m(i) = im$. Let $M_I := \{g_m \mid m \in M\}$. Then $M_I$ is an $R$-submodule of $M$ and $$\Ext^1_R(R/I, M) \cong \Hom_R(I,M) / M_I.$$ Is that a nice description? — neilme Apr 26 '13 at 7:12
I'll try to get back to this later, depending on how much time I have. But I certainly intend to help with editing such posts (and possibly flagging some of such comments.)
 
Martin Sleziak
Martin Sleziak
6:25 AM
data-explorer The queries mentioned above do not work perfect. For example, when searching for macro called \name, they pick also stuff such as \ name or \,name. Searching for \C find also matrix A&B\\C&D. And I think \C also picks up \cos.
Maybe something like this could be useful for such situations?
For comparison: Comments with \C and Posts with \C
 
Martin Sleziak
Martin Sleziak
7:36 AM
I will look at the one with the definition in the title later: $\DeclareMathOperator{\ord}{ord}\gcd(\ord(a),\ord(b)) = 1$ then $\ord(ab)=\ord(a)\cdot \ord(b)$ where $a,b$ do not commute. (I am not sure whether after the expansion the will still fit the character limit.)
And I have flagged three of those four comments that the query found. (The fourth one is ok.)
My attempt for small x: \begin{align} I(x) &= \frac{1}{2\pi}\int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} e^{x \cos^2(\theta)}d\theta\\ &= \frac{1}{2\pi}\int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} d\theta [1 + x\cos^2{\theta} + \order{x^2}]\\ &= \frac{1}{2\pi}\int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} d\theta [1 + \frac{x}{2}(1+\cos{2\theta}) + \order{x^2}]\\ &\approx \frac{1}{2\pi} [\pi + \frac{x}{2}(\pi)] \end{align} Therefore, \begin{align} &\boxed{ I(x)\approx \frac{1}{2} + \frac{x}{4} \text{for small $x$}} \end{align} — niagarajohn Nov 18 '18 at 14:53
Thank you for responding. I mean that $\mathfrak p_v$ is the prime ideal of $K$ corresponding to the place $v$, $(\mathfrak p_v, L/K)$ is the Frobenius element, and this automorphism is raised to the power of $ord_v(x)$, which is the normalized valuation of $K$ (so that $\ord_v(\mathfrak p_v) = 1$). — D_S Feb 10 '15 at 0:51
Nope, because $-7 =21$. In your $G$, the element $7$ has order $4$. The elements of order $7$ in $\mathbb{Z}_{28}$ are $4, 8, 12, 16, 20, 24$. In general, in $\mathbb{Z}_{n}$ the oder of $m$ is $\ord(m)=\frac{n}{\gcd (m,n)}$. — N. S. Aug 27 '12 at 15:39
In this one, \ord is not used in math mode:
Hi, welcome to Math.SE. I just edited your post to make a few things clearer. Note that you can use \pmod{number here}. Also, it usually helps to split things into separate lines to make things easier to read. I'm not sure what you were trying to do with \ind and \ord by the way. If you could tell me, I can tell you the correct syntax for them :). — Joe Jul 2 '12 at 20:37
Maybe I should have used just a single flag and include the link to the query?
in Math Meta Chat, 2 hours ago, by Martin Sleziak
Regarding flagging - if I can find a query where all (or almost all) of the comments it returns have this problem, it would probably be better to use a single flag with a link to the query rather than flag each comment separately, right? Example: Comments with \Hom.
 
 
2 hours later…
Martin Sleziak
Martin Sleziak
9:49 AM
 
 
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Martin Sleziak
Martin Sleziak
11:37 AM
 
 
2 hours later…
Martin Sleziak
Martin Sleziak
1:31 PM
@MartinSleziak From the posts found by the SEDE query for \Ext, only two needed fixing: math.stackexchange.com/posts/2066051/revisions and math.stackexchange.com/posts/1593880/revisions
 
 
4 hours later…
Martin Sleziak
Martin Sleziak
5:08 PM
This post explains:
5
A: Uses for esoteric integral symbols

Jack HenahanWell, \sqint is the quaternion integral and \fint is used for integral averages, if memory serves. I'll have to look around for the others, though.

However I see two posts with \fint - without this being defined anywhere.
0
A: Completeness of $(BMO(\Bbb R^n),||\cdot||_{\ast})$

JoeIt is well known that if $f \in \text{BMO}(\mathbb R^n)$, then for any $\epsilon > 0$ there exists a ball $B$ with center $x_0$ and radius $R$ such that \begin{equation}\label{3} R^\epsilon \int_{\mathbb R^n} \frac{|f(x) - f(B)|}{(R + |x - x_0|)^{n + \epsilon}} \, dx \leq C_{n,\epsilon} \|f\|_*\;...

3
A: Will the Lebesgue integral of a real valued function always be a Riemann sum?

PhoemueXThere are (at least) two ways to interpret your question. The first is that you are asking if the value of the integral is actually given by a Riemann sum. This is not the case, even for Riemann integrable functions. Consider for example the function $$ f:\left[0,1\right]\to\mathbb{R},x\mapsto\be...

AFAIK the \strokedint or \fint commands are not implemented in MathJax, so I just replaced it by the definition. — Willie Wong Jul 10 '12 at 11:02
0
Q: Differentiating the following average.

TheoremI am trying to find $\frac{\partial ^2}{\partial r^2} \frac{1}{|\partial B(x,r)|} \int_{\partial B(x,r)} u(y,t)\mathrm{d}y $ . Where $B$ is a ball of radius $r$ with center at $x$ . Differentiating once was ok , but i couldn't not again differentiate . Thank you for your help .

multivariable-calculus pde
@GiuseppeNegro If $u$ is subharmonic then $u(x) \leq \fint u$. But the converse is obviously not true. — OhDaeSu Aug 29 '18 at 9:45
@OhDaeSu: Does \fint u mean $\frac{1}{|B|}\int_B u$? In that case, it is true that $u(x)\le \frac{1}{|B|}\int_B u$ for all balls centered at $x$ if and only if $u$ is subharmonic in some sense. I am not fresh in these things but they are in the linked book, I'm sure — Giuseppe Negro Aug 29 '18 at 9:57
5
A: How can I do this symbol (integral with a barre) in latex?

Steven B. SegletesSome fonts have such an integral sign built in, but if not, you can always stack a - or $-$ over one. \documentclass{article} \usepackage{stackengine} \stackMath \begin{document} $\stackinset{c}{}{c}{}{\mkern1.5mu\mbox{-}}{\int}x\,dx$ $\displaystyle\stackinset{c}{}{c}{}{-\mkern4mu}{\displaystyle...

> Built in examples include versions with a slanted bar (denoted \fint) as well as some versions with a horizontal bar.
> Those packages with a slanted \fint include: txfonts, pxfonts, esint, and stix.
1
A: Average integral symbol

José Figueroa-O'FarrillThere is a very useful site for this sort of questions. It is a hand-writing interface to the comprehensive LaTeX symbol list: you draw the symbol you are looking for in a box (using your mouse,...) and the software tries to recognise it. You can teach the software by telling it which one (if a...

> I tried it with the average integral symbol and it suggested the command \fint in the esint package. That package seems to contain a number of ornamented integral signs.
2
Q: double integrals with a bar

user110191I usually use \fint to denote normalized integration. I would like to produce the same slanted line across a double integral \iint. The command \fiint does not seem to exist. How can I get this notation for normalized double integrals?

stacking-symbols
5
A: How can I do this symbol (integral with a barre) in latex?

BernardThe symbol already exists in esint: \documentclass[ a4paper]{article} \usepackage{mathtools} \usepackage{esint} \newcommand*{\dd}{\mathop{}\!\mathrm{d}} \begin{document} \[ \fint_{\partial\mathrlap{B_{R}}}u(y)\dd y \]% \end{document}

 
Martin Sleziak
Martin Sleziak
5:44 PM
I have edited one more post math.stackexchange.com/posts/2140258/revisions and flagged the comment containing the same macro:
Thank you in particular for the last part "Thus not only can we construct an isomorphism, but we can even consider $\Cl$ to just be $\Lambda V$ with extra structure" -- this was exactly what I was most worried/concerned about. Again, I really appreciate your help -- this had been bugging me about geometric/Clifford algebras almost as soon as I learned the constructions of $\Lambda V$ and $\Cl$ from the tensor algebra, because the quotient ideals looked fairly different and perhaps "incompatible" to me, so I wasn't sure how to prove or disprove that. Your answer addresses all of this well. — Chill2Macht Feb 15 '17 at 17:21
 

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