How to label a figure outside of the float environment?
Why does an environment's label have to appear after the caption?
Edits on closed posts Should questions or answers on questions that are closed be edited, even if the question is closed and the edit does not change anything about the reason it's closed? Example:  was just edited, which I saw in the review queue. It certainly improves the answer, but since the answer doesn't really have to exist on SE at all (because the question is off-topic), should this edit be made? In my understanding, the only reason that the edit option for a closed question is not greyed out is so that it can be edited to make it comply with the SE rules. How to efficiently count the number of keys/properties of an object in JavaScript? How to check if a macro value is empty or will not create text with plain TeX conditionals? I have a macro which holds some text value, e.g. \macro{some text}. If it is empty, I would like for nothing to appear in the document, but it has some content of any kind which would produce text displayed in the document, I would like a message to appear, "Text: some text".   \macro{} would be considered empty. \def\somedata{}, \macro{\somedata} would be considered empty. \macro{0} would be considered not empty.   I have tried making a TeX conditional which can check if the value is not empty, but nothing I tried works, e.g.:  \ifx #1 {} \else     Text: #1 \fi  \ifx#1{} \else     Text: #1 \fi  \ifx #1 \nil \else     Text: #1 \fi  \ifx#1!="" \else     Text: #1 \fi   What is the correct syntax for creating a conditional in plain TeX with checks if a value is not empty? print IP address with interface name I want to show the IP address like below  lo : 127.0.0.1  eth0 : 192.168.5.123 eth1 : 192.172.0.212 wlan0 : 10.1.0.124   I'm able to print all IP address by ifconfig | awk '/inet addr/{print substr($2,6)}'. But it is only printing the IPs. Every system have their own interface names and addresses. So my script has to show their interfaces with respect to IP addresses. Selecting one every n frames from a video using ffmpeg This is the proof from the book:     Theorem. There are infinitely many primes of the form $4n+3$.    Lemma. If $a$ and $b$ are integers, both of the form $4n + 1$, then the product $ab$ is also in this form.  Proof of Theorem: Let assume that there are only a finite number of primes of the form $4n + 3$, say  $$p_0, p_1, p_2, \ldots, p_r.$$ Let $$Q = 4p_1p_2p_3\cdots p_r + 3.$$ Then there is at least one prime in the factorization of $Q$ of the form $4n + 3$. Otherwise, all of these primes would be of the form $4n + 1$, and by the Lemma above, this would imply that $Q$ would also be of this form, which is a contradiction. However, none of the prime $p_0, p_1,\ldots, p_n$ divides $Q$. The prime $3$ does not divide $Q$, for if $3|Q$  then $$3|(Q-3) = 4p_1p_2p_3\cdots p_r,$$ which is a contradiction. Likewise, none of the primes $p_j$ can divides $Q$, because $p_j | Q$ implies $p_j | ( Q - 4p_1p_2\cdots p_r ) = 3$, which is absurd. Hence, there are infinitely many primes of the form $4n +3$.   END  From "however, none of the prime ...." to the end, I totally lost!    My questions:   Is the author assuming $Q$ is prime or is not? Why none of the primes $p_0, p_1,\ldots, p_r$ divide $Q$? Based on what argument?     Can anyone share me a better proof?     Thanks. Does there exist a continuous function such that f(x) is rational for every irrational x, and f(x) is irrational for every rational x? Does there exist a continuous function such that f(x) is rational for every irrational x, and f(x) is irrational for every rational x? I can think of examples where this would be true, but I'm having a lot of trouble with the continuity. The current top-voted to  states:     Another one that's not so much a security issue, although it is security-related, is complete and abject failure to grok the difference between hashing a password and encrypting it. Most commonly found in code where the programmer is trying to provide unsafe "Remind me of my password" functionality.   What exactly is this difference? I was always under the impression that hashing was a form of encryption. What is the unsafe functionality the poster is referring to? How to determine which form has been submited and to validate them in a servlet Difference between SQL batch, statement and RPC? What is the difference between SQL batch, T-SQL statement and Remote Procedure Call? How can I tell if part of the T-SQL code is a batch or statement? Confirm and agree to negative questions Suppose we have two short exact sequences in an abelian category $$0 \to A \mathrel{\overset{f}{\to}} B \mathrel{\overset{g}{\to}} C \to 0 $$ $$0 \to A&#39; \mathrel{\overset{f&#39;}{\to}} B&#39; \mathrel{\overset{g&#39;}{\to}} C&#39; \to 0 $$ and morphisms $a : A \to A&#39;, b : B \to B&#39;, c : C \to C&#39;$ making the obvious diagram commute. The snake lemma states that there is then an exact sequence $$0 \to \ker a \to \ker b \to \ker c \to \operatorname{coker} a \to \operatorname{coker} b \to \operatorname{coker} c \to 0$$ where the morphisms between the kernels are induced by $f$ and $g$ while the maps between the cokernels are induced by $f&#39;$ and $g&#39;$.  It is not hard to show that the morphisms induced by $f, g, f&#39;, g&#39;$ exist, are unique, and that the sequence is exact at $\ker a, \ker b, \operatorname{coker} b, \operatorname{coker} c$. With the use of a somewhat large diagram shown , we can even construct the connecting morphism $d : \ker c \to \operatorname{coker} a$. However, I'm stuck showing exactness at $\ker c$ and $\operatorname{coker} a$. I thought Freyd might have had an element-free proof in his book, but it turns out he proves it by diagram chasing and invoking the Mitchell embedding theorem [pp. 98–99]. Is there a direct proof? Group With an Endomorphism That is "Almost" Abelian is Abelian. Suppose a finite group has the property that for every $x, y$, it follows that   \begin{equation*} (xy)^3 = x^3 y^3. \end{equation*}  How do you prove that it is abelian?    Edit: I recall that the correct exercise needed in addition that the order of the group is not divisible by 3. Variable-name \newcommand with parameters within another \newcommand How do I disable Aero Shake in Windows 7? I'm always accidentally minimizing most of my windows. This is really annoying. How do I disable Aero Shake? How to upload files to server using JSP/Servlet? Could anyone provide an example of a nonempty subset $U$ of $R^2$ such that $U$ is closed under scalar multiplication, but $U$ is not a subspace of $R^2$ What's the difference between iterating over a file with foreach or while in Perl? Why use sucrose rather than glucose in an injectable vaccine? These are the ingredients of :  Medicinal:  mRNA  Non-medicinal:  ALC-0315 = ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate) ALC-0159 = 2-[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide 1,2-Distearoyl-sn-glycero-3-phosphocholine cholesterol dibasic sodium phosphate dihydrate monobasic potassium phosphate potassium chloride sodium chloride sucrose water for injection   Sucrose is broken up into glucose and fructose by digestion, and so it normally never enters the blood system. Yet here, it is being directly injected into the body. What happens to this sucrose when it enters the blood system, and why choose sucrose rather than the more standard glucose (dextrose)? I am executing my ./shell.sh which contains   eval "$(pyenv init -)" pyenv shell 3.8.2   But nothing happens. If i run this code in bash manually it works fine and shell version of python switches from 2.7.10 to 3.8.2.  I am in the right directory and I gave the .sh file execution permissions.