When I try to compile some TeX code from a few years ago that relies on the  package, I get the following error: ! LaTeX3 Error: Mismatched LaTeX support files detected. (LaTeX3)        Loading 'expl3.sty' aborted! (LaTeX3)         (LaTeX3)        The L3 programming layer in the LaTeX format (LaTeX3)        is dated 2021-02-18, but in your TeX tree the files require (LaTeX3)        at least 2021-05-11.  For immediate help type H &lt;return&gt;.  ...                                                                                                  l.77      \ExplLoaderFileDate{expl3.sty}}                                          %  The code itself is not relevant; the error can be reproduced by compiling, say, the following MWE: \documentclass{article}  \usepackage{siunitx}  \begin{document}  \SI{1}{\s}  \end{document}  I have just updated my TeX Live 2021 distribution and furthermore I haven't encountered this error before. How do I fix this?
Background I updated my TeX Live installation on my Mac a while ago and got the error LaTeX3 Error: Mismatched LaTeX support files detected. I found a solution at .  As far as I understand it (which isn't very far), there are system formats and local formats, and TeX Live is updating the wrong one.  The fix is to update the formats. Using fmtutil-user --all worked for me.  It spewed out a load of stuff, then output fmtutil [INFO]: log file copied to: /Users/&lt;user&gt;/Library/texlive/2020/texmf-var/web2c/luatex/dvilualatex.log fmtutil [INFO]: /Users/&lt;user&gt;/Library/texlive/2020/texmf-var/web2c/luatex/dvilualatex.fmt installed.  I don't know what this tells me, but my TeX Live preferences has TeX programs set at /Library/TeX/texbin, which seems to be a link to /usr/local/texlive/2020/bin. Problem Every time I update TeX Live, I have to apply the solution again. Question Is there a way to make TeX Live use the correct formats permanently so that I don't have to keep running fmtutil-user --all after every TeX Live update?  Extra information  to  check if you have some local formats around which hide the system formats. (with eg kpsewhich --all --engine=pdftex pdflatex.fmt)  When I did that, it output /Users/&lt;user&gt;/Library/texlive/2020/texmf-var/web2c/pdftex/pdflatex.fmt /usr/local/texlive/2020/texmf-var/web2c/pdftex/pdflatex.fmt  but I don't know what that's telling me.
How to increase ping time/network connection latency on Windows? I need to permanently increase network latency in approximately 100ms, without losing packets.  Reason: On a certain server and internet game my ping is too much lower than the other people playing it. I have 15ms, when average is 150ms which gives me cheater-like advantages.  So also out of curiosity I'm looking for ways to increase my ping while keeping connection stable. What are my options if any?  I thought about VPN services, but it seems like a bad option since games use UDP?  Is there any router/software that would assist me on this?  I'm on windows. why could a check if (document.addEventListener) returns false What resampling method is used in the raster 'Save as...' dialog? I received a raster that was resampled using the Save as dialog in QGIS. Now I need to describe the resampling process in a report. But I could not figure out the method used in the resampling. Is it Nearest Neighbor? Bicubic?  This question has been asked before () but the answer does not specify the method used.   I also tried looking at the QGis source code in GitHub, but unfortunately, I could not find where the magic takes place (I'm not a programmer) $G$ a group s.t. every non-identity element has order 2. If $G$ is finite, prove $|G| = 2^n$ and $G \simeq C_2 \times C_2 \times\cdots\times C_2$ Let $G$ be a group s.t. every non-identity element has order 2. If $G$ is finite, prove $|G| = 2^n$ and $G \simeq C_2 \times C_2 \times\cdots\times C_2$  I know G is abelian since $ab = (ab)^{-1} = b^{-1} a^{-1} = ba$ for all non-trivial $a,b \in G$ so I have several questions remaining:    How do I prove $|G| = 2^n$? I'd like to say we use induction to prove this but I'm at a loss as to where I would start. Why is $G \simeq C_2 \times C_2 \times\cdots\times C_2$?   I've read several answers to question similar to this yet unfortunately most of them involve Galois Fields and vector spaces, both concepts I'm unfamiliar with. I'd greatly appreciate an intuitive proof. Show that$\displaystyle\sum_{n=1}^\infty\frac{\sin( nz)}{n}$ diverges if $\mathfrak{Im} \,(z)\neq0$ We have to show that$\displaystyle\sum_{n=1}^\infty\frac{sin( nz)}{n}$ diverges if $Im\,(z)\neq0$  My try:$$\sin (nz) = \mathfrak{Im}(e^{nzi})$$  $$\sum_{n=1}^{\infty} \frac{\sin nz}{n} = \mathfrak{Im} \sum_{n=1}^{\infty} \frac{(e^{zi})^n}{n} = - \mathfrak{Im} \ln\left(1-e^{zi}\right). $$ Then how to proceed? /etc/sysctl.conf doesn't persist after reboot Two homologous but not homotopic loops on a closed surface of genus greater than one Suppose $S$ is a closed surface with genus greater than $1$. Give an example of two loops on $S$ which are not homotopic, but are homologous to each other.   I need help solving this question. I have read the Wikipedia page on it and I realize that it does not contain the necessary knowledge to visualize this problem.  And I was also wondering the relation between the fundamental group $\pi_1(S)$ and the first homology group $H_1(S)$? Some restrictions is that $S$ is a closed surface and the genus is greater than $1$. How to programmatically send SMS on the iPhone? introduces  which will allow the introduction of new literal syntax based on existing literals (int, hex, string, float) so that any type will be able to have a literal presentation.  Examples:  // imaginary numbers std::complex&lt;long double&gt; operator "" _i(long double d) // cooked form {      return std::complex&lt;long double&gt;(0, d);  } auto val = 3.14_i; // val = complex&lt;long double&gt;(0, 3.14)  // binary values int operator "" _B(const char*); // raw form int answer = 101010_B; // answer = 42  // std::string std::string operator "" _s(const char* str, size_t /*length*/)  {      return std::string(str);  }  auto hi = "hello"_s + " world"; // + works, "hello"_s is a string not a pointer  // units assert(1_kg == 2.2_lb); // give or take 0.00462262 pounds   At first glance this looks very cool but I'm wondering how applicable it really is, when I tried to think of having the suffixes _AD and _BC create dates I found that it's problematic due to operator order. 1974/01/06_AD would first evaluate 1974/01 (as plain ints) and only later the 06_AD (to say nothing of August and September having to be written without the 0 for octal reasons). This can be worked around by having the syntax be 1974-1/6_AD so that the operator evaluation order works but it's clunky.   So what my question boils down to is this, do you feel this feature will justify itself? What other literals would you like to define that will make your C++ code more readable?    Updated syntax to fit the final draft on June 2011 Isometries of the sphere $\mathbb{S}^{n}$ Got this as homework and I don't know how to tackle this. Help please!  Prove that the isometries of $\mathbb{S}^{n} \subset \mathbb{R}^{n+1}$, with the induced metric, are restrictions to $\mathbb{S}^{n}$ of the linear orthogonal transformations. Automorphisms of the complex plane How can it be shown that $$Aut(\mathbb{C})=\{f|f(z)=az+b,a\neq 0\},$$ where an automorphism of $\mathbb{C}$ is defined as a bijective entire function with entire inverse?  If $f$ is of the form $f(z)=az+b$, with $a\neq 0$, then obviously $f$ is in $Aut(\mathbb{C})$. How can I prove the converse? Preface: Every couple of days there comes a question of this type, which is easy to solve with sed, but takes time to explain. I'm writing this question and answer, so I can later refer to this generic solution and only explain the adaption for the specific case. Feel free to contribute.  I have files with variable definitions. Variables consist of uppercase letters or underscore _ and their values follow after the :=. The values can contain other variables. This is Gnom.def:  NAME:=Gnom FULL_NAME:=$FIRST_NAME $NAME FIRST_NAME:=Sman STREET:=Mainstreet 42 TOWN:=Nowhere BIRTHDAY:=May 1st, 1999   Then there is another file form.txt with a template form:  $NAME Full name: $FULL_NAME Address: $STREET in $TOWN Birthday: $BIRTHDAY Don't be confused by $NAMES   Now I want a script which replaces the variables (marked with $ and the identifier) in the form by the definitions in the other file, recursively, if necessary, so I get this text back:  Gnom Full name: Sman Gnom Address: Mainstreet 42 in Nowhere Birthday: May 1st, 1999 Don't be confused by $NAMES   The last line is to ensure that no substrings of variables get replaced accidentally. Which Distribution Does the Data Point Belong to? CodeIgniter/PHP Active Record won't increment an integer Consider an inviscid Burgers equation:  $u_t + u u_x = 0.$  With the initial data:  $ u(x,0) = \left\{ \begin{array}{ll}              0  \quad  &amp; \text{if} \quad x &lt; 0, \\[0.5em]              1  &amp; \text{if} \quad x &gt; 0.\end{array} \right. $  Possible weak solutions to this problem include, for example:  $ u_1(x,t) = \left\{ \begin{array}{ll}              0  \quad  &amp; \text{if} \quad x &lt; t/2, \\[0.5em]              1  &amp; \text{if} \quad x &gt; t/2.\end{array} \right. \hspace{10mm} $   $ u_2(x,t) = \left\{ \begin{array}{lll}              0  \quad  &amp; \text{if} \quad x &lt; 0, \\[0.5em]                      x/t &amp; 0 &lt; x &lt; t,\\[0.5em]              1  &amp; \text{if} \quad x &gt; t.\end{array} \right. $  Every material that provides such examples states that it is easy to check that these are both solutions of our problem. I do not see how that is done.  I know how to obtain the equation:  $ \int_{0}^\infty \int_{-\infty}^\infty [ q \phi_t + f(q) \phi_x ] dx dt + \int_{-\infty}^\infty q(x,0) \phi(x,0) dx = 0,  $  But I do not see how to "test" if the weak solutions provided above satisfy this. I tried writing the solutions as Heavside functions and integrating them, but I am not sure how to handle an arbitrary test function.  I assume there are some solution I could construct that would not be the weak solution to our initial data, how to check that? sed delete option change of delimiter Where can I get an Ubuntu Installation CD/DVD/USB? I need to upgrade my existing Ubuntu system, and I also want to install Ubuntu on a new laptop.  I would like to have an installation CD or DVD to do both of these.  Where exactly I can order or request an Ubuntu installation CD/DVD/USB? Show that if $f:X\to Y$ is a continuous function if and only if the graph of $f$ is a closed subset of $X\times Y$ Mean Time to Failure (MTTF): When disk manufacturers post this, how should you interpret their numbers? Mean Time to Failure (MTTF) is usually given in terms of hours, and by doing some calculations, it seems that a disk should fail only after a good number of years have gone by.  It seems that disks need repair more often than that. Does anyone know why this is so?  I figured that there is something fishy about this metric. Am interpreting something wrong here? I have the following query:  select column_name, count(column_name) from table group by column_name having count(column_name) &gt; 1;   What would be the difference if I replaced all calls to count(column_name) to count(*)?  This question was inspired by .    To clarify the accepted answer (and maybe my question), replacing count(column_name) with count(*) would return an extra row in the result that contains a null and the count of null values in the column.