The question rooted from the comment of J.R. on  He edited my answer making 'a doubt' 'doubts'. In the comment it's mentioned that if I'm suspicious about something, generally it's expressed in a plural way. But in my answer, I had only one doubt that she meets someone which is out of my knowledge.  Now the question:   If I'm suspicious about only one thing, do I have a doubt? or doubts?  Note: In India, as I said there in my comment, it's quite clear. I have a doubt if I have a doubt and I have doubts if I have them many. In fact, I have many doubts is also common. In my dialect, I'm clear and pretty sure about it but posting this question to learn further.
To my (British) ear, it never sounds correct to say you have a doubt about something.  I expect that doubt to be pluralised, even if there's only one specific thing that I'm doubtful of, in one specific way, so I would always say "I have doubts about something".  Answers to  say that using doubt as a synonym for question is "Indian English". That seems to be the case in  which starts with "I have a doubt on my construction", because the OP really is saying "I have a question" (which he goes on to actually ask). Okay, it should have been a question/doubt about something, not on, but I'm not concerned with that detail here.  But in  the OP says "...there is a doubt that can I use [some construction]". In that case it's not easy to see how the word doubt can be replaced with question.  I don't have a problem with, for example, , because there I interpret it as doubt=uncertainty (a state of mind, syntactically equivalent to words like happiness, agitation, sorrow, etc.). But you certainly can't "have a happiness about something". So my question is...     Is it acceptable today to use singular noun doubt in any contexts where it means something other than state of mental uncertainty? If so, what are those contexts?
Removing the first line of CSV file What does **Ens** stand for? Earlier someone was asking about the category "Ens" described in Categories for the Working Mathematician. My question is more basic: What does Ens stand for?  Most of the categories have names that are self explanatory, and maybe this one does too.  But for the life of me I can't think of it, and a Google search was no help. I have seen similar questions on the matter (, ) of adding vertical space and not breaking vertical lines, the solutions suggested are to add space after the \\ using \\[0.1cm] for example or changing the \arraystretch which I do not want to do. Using \\[0.1cm] allows me to add space just before a \hline but not after as well.  How can I add vertical space after a \hline without breaking vertical lines in a table?  Please find my MWE below:  \documentclass{scrreprt} \usepackage{setspace} \usepackage[left=2.5cm,right=2.5cm,top=3cm,bottom=3cm]{geometry} \usepackage{array,tabularx} \doublespacing  \begin{document} \begin{table}[htb]   \centering   \onehalfspacing   \caption{Table of info.}      \begin{tabular}{c | c c}  &amp; C/S Analyser &amp; O/N/H Analyser \\  &amp; EMIA 320 V2 &amp; EMGA 830 \\[0.1cm]    \hline    \noalign{\vskip 0.1cm} Sensitivity (ppm) &amp; 0.1 &amp; 0.001 \\ Furnace type &amp; Induction &amp; Impulse \\ Carrier gas &amp; Pure O2 &amp; Pure He \\[0.1cm]    \hline     \end{tabular}    \doublespacing   \label{tab:chem} \end{table} \end{document} How to catch and print the full exception traceback without halting/exiting the program? Measuring accuracy of a logistic regression-based model Reading a file used by another process Cardinality of a set A is strictly less than the cardinality of the power set of A I was reading a book and this sentence seemed a little odd to me:     At approximately 19.45 hours the two men rose, stretched and yawned. They picked up their gear and stood at the door, ...   What does the first part mean? If it's the exact time, shouldn't it be 19:45? And if it's duration, shouldn't it be "After 19.45 hours"?  (The story here happens at an airbase, if it's of any relevance)    Edit: The book I've quoted is this:   by John Creed.   The author is Irish and the text is set in northern England/Ireland. What special characters must be escaped in regular expressions? I am tired of always trying to guess, if I should escape special characters like '()[]{}|' etc. when using many implementations of regexps.  It is different with, for example, Python, sed, grep, awk, Perl, rename, Apache, find and so on. Is there any rule set which tells when I should, and when I should not, escape special characters? Does it depend on the regexp type, like PCRE, POSIX or extended regexps? Include the option to flag posts as spam in the Low Quality queue I guess this is an additional to previous requests like  and .  But I just came across  review item, and was unable to flag it as spam.  edit: Since I posted this, the item has been removed (deleted) here is a screenshot: Is Duck/Duct tape safe to use to insulate mains wires? Question says it all really. Based in the UK so mains is 240v and 20 amps. It's a lighting circuit. What is the importance of the Diophantine inequality $\frac{1}{p} + \frac{1}{q} + \frac{1}{r} > 1$? In Humphreys' book  Introduction to Lie algebras and Representation Theory(3rd printing, p.62), the Diophantine inequality $$\frac{1}{p} + \frac{1}{q} + \frac{1}{r} &gt; 1$$ appeared while classifying all Coxeter graphs of irreducible root systems. Under the assumption $p \geq q \geq r \geq 2 $, the possible triples turn out to be $(p,2,2), (3,3,2),(4,3,2),(5,3,2)$, which correspond to the Coxeter graph $\text{D}_{p+2}, \text{E}_6, \text{E}_7, \text{E}_8$, respectively.  It seems quite straightforward to solve the inequality in positive integers, but Humphreys said that      This inequality, by the way, has a long mathematical history.   without further comment. So I want to know if this Diophantine inequality has any important significance, or if it has appeared in other context (maybe relevant history) before. Scoring when two triple word squares are covered in one play The word QUAGMIRE is on the board vertically, with the Q on the top row, second column. The next player creates SQUEEZED horizontally, landing the S on the triple word square in the top row, first column, and remaining UEEZED landing to the right of the existing Q, ending with the D on the triple word square in the eighth column. Since two triple word squares are covered in this one placement, how would it be scored?  Letters:   S: 1 Q: 10 U: 1 E: 1 x 2 (double letter) E: 1 Z: 10 E: 1 D: 1   27 Total for letters. Do you then multiply by 3 for the first triple word square, and then multiply that result by 3?  27 X 3 = 81, 81 X 3 = 243  Bonus for all 7 tiles placed:  243 + 50 = 293 Lightning New Case action override I have action override on New Case button which runs our custom component.  As you know, we can create a new Case from different places in org, e.g. from related lists. When creating a Case from related list on Account using standard action in Lightning we have prepopulated AccountId to the lookup field. Is it possible to do the same with custom component? I can't catch the AccountId using force:hasRecordId, because action override redirects me to the new page with custom component where I don't have a context of Account. URL also doesn't contain its Id. What can I do to grab Id of context object and populate it to my component? The shellscript is very simple:  retroarch $* -c /tmp/retroarch/Data/retroarch/gambatte.cfg   ("retroarch" is another shellscript)  If the filename passed contains spaces it fails:  RetroArch [ERROR] :: Could not read ROM file. Does an unpublished document you upload to ResearchGate count as prior publication when submitting to a journal? On ResearchGate, if you upload something like a thesis, and then it says publish resources, does this mean the thesis becomes properly published in the sense of the usual requirements of journals that there be no prior publication of the submitted work?   I ask because I’m drafting thesis chapters into journal articles and did not choose to publish the thesis as a whole work in order to do so, so I want to make sure that by clicking publish resources I am not actually publishing the copy I’ve uploaded, I’m just making it publicly available? Does this mean it becomes published despite it not technically being a published work? (If so, I’ll just remove the copy I uploaded). Is my proof that $U_{pq}$ is not cyclic if $p$ and $q$ are distinct odd primes correct? Prove that $U_{pq}$ is not cyclic if $p$ and $q$ are distinct odd primes.   I am a self taught person. I just learned this and tried this on my own and came up with this.  $x \equiv 1 \pmod{p}$ and $x \equiv -1 \pmod{q}$ has a solution $[a]_{pq}$, since $p$ and $q$ are relatively prime. Because $q$ is an odd prime, $[-1]_{pq}$ is not a solution, so $[a]_{pq}\neq [-1]_{pq}$. But $a^2 \equiv 1 \pmod{p}$ and $a^2 \equiv 1 \pmod{q}$, so $a^2 \equiv 1\pmod{pq}$ since $p$ and $q$ are relatively prime, and thus $[a]_{pq}$ has order 2.  Can someone please tell me if this proof this correct? Please help with proof as I learned it just now as a self taught person. Let $a=p_1^{x_1}p_2^{x_2}\cdots\cdot p_q^{x_q}$ and $b=p_1^{y_1}p_2^{y_2}\cdots p_r^{x_r}$ ,   say — Since gcd(a,b) is the largest common divisor of a and b and is divisible by any other common divisor of the two,   GCD$(a,b)=p_1^{\min(x_1,y_1)}p_2^{\min (x_2,y_2)} \cdots p_q^{\min (x_q,y_q)}$  LCM$(a,b)= p_1^{\max(x_1,y_1)}p_2^{\max(x_2,y_2)}\cdots p_r^{\max (x_r,y_r)}$  I understand GCD(a,b) has to divide both $a,b$. Therefore the exponent of any prime factor $p_i$ in GCD has to be in both $a,b$  — therefore $p_i^{\min(x_i, y_i)}$. But I'm muddled and anxious. Why does $\min$ appear in GREATEST common divisor? Why does $\max$ appear in LOWEST common multiple? Prove that $\lambda = 0$ is an eigenvalue if and only if A is singular. Is it feasible to build an index of prime factors? Would it be possible to break an RSA key, in for example 1 week of time, if the cracker have already spent X number of years building an index of primes by performing every permutation of existing prime keys up to $2^{2048}$?  I understand this would take an immense amount of time to do, but it would only be done once. Obviously, computing such an index would take a considerable amount of time and would have to be done with someone having the right amount of resource. Given the public key, you would be able to look up what the two primes are, and hence retrieve the private key instantly.  Breaking an 256 AES would then be easier, as AES keys are often generated using the RSA private key.  Would it be possible to build such an index? How long would that take in permutations and perhaps with the fastest computer in the world?