This is an all too common problem. I spent ~1hr debugging an answer an some SE site. Until I realized it was a simple typo. I had yet to make an account (usually just mooching off of other's answers as so many do), but I decided to help out the community by commenting on the answer and showing the typo. After going through the process of making an account - I realized I can't even comment yet!  I'm wondering how many typos are still out there on that SE site, because of these limits! What gives?
Users with less than 50 reputation points cannot write comments on questions and answers that they don't own.  Why does this limit exist? But I want to contribute now. What should I do instead? But I can't write a good answer without more information! Shouldn't I be allowed to post comments if I have reputation on a different site? But I saw a new user posting a comment! How did they do it? Why do I need 50 reputation to comment on my own post?   See also:    in the Help Center
Why is the notation $\frac{\partial f}{\partial x}$ used? how to turbo boost my cpu on Ubuntu? My PC has one Intel Haswell i5 4690, which is supposed to be boosted up to 3.9GHz from the regular frequency 3.5GHz. I do not know if it is possible to use some softwares to turbo boost this cpu on Ubuntu 14.04LTS. THX! Difference between >> and >>> in verilog? What is the difference between &gt;&gt; and &gt;&gt;&gt; in verilog/system verilog? I know that == tests for only 1 and 0, while === tests for 1, 0, X, Z. So how is that similar to the shift operator? "Print" and "ui.Label" return different strings in console and in the UI in Google Earth Engine I am working on a variable label in Google Earth Engine and noticed that the label as printed in the console is not the same as the label shown on the map. Why is that? Code below:  var aoi = ee.Geometry.Polygon([[[-106.75701284923326, 42.31332966408458],           [-106.75701284923326, 42.003856624775146],           [-106.31755972423326, 42.06913460511273]]]);  var chirpsSelect = ee.ImageCollection("UCSB-CHG/CHIRPS/DAILY")             .filterDate('1985-01-01','2018-01-01')             .filter(ee.Filter.dayOfYear(3,6))             .filterBounds(aoi)  var chirpsStartImage = ee.String(chirpsSelect.first().get('system:index')) var dateStartString = ((((chirpsStartImage.slice(6,8)).cat('/')).cat(chirpsStartImage.slice(4,6))).cat('/')).cat(chirpsStartImage.slice(2,4))   var sortChirpsSelect = chirpsSelect.sort('system:index',false)  var chirpsEndImage = ee.String(sortChirpsSelect.first().get('system:index')) var dateEndString = ((((chirpsEndImage.slice(6,8)).cat('/')).cat(chirpsEndImage.slice(4,6))).cat('/')).cat(chirpsEndImage.slice(2,4)) var dateTitle = ee.String((dateStartString.cat(' to ')).cat(dateEndString))  print(dateTitle)  var dateLabel = ui.Label({   value: dateTitle })  var panel = ui.Panel() panel.add(dateLabel) Map.add(panel) Aufbau principle in modern quantum theory Does D&D 5e have a rule for character knowledge about monsters? In the 3rd and 4th editions of D&amp;D, there were explicit rules for determining if a character knew anything about a monster before them.  In 3rd edition, for example, use of the  skill with a general DC of 10 + the monster's HD allowed for determining one fact, plus one fact per 5 points over the check.  Looking at the Intelligence section of the 5e PHB, I don't see any similar notation.  Does 5e provide any guidance as to when a player could use their out-of-game knowledge about a monster, or when the player might be told things their character would probably know in-game? What compiler warning level do you recommend for different C/C++ compilers?  gcc and g++ will let you get away with a lot on the default level.  I find the best warning level for me is '-Wall'.  And I always try to remove fix the code for the warnings it generates.  (Even the silly ones about using parenthesis for logical precedence rules or to say I really mean 'if (x = y)')  What are your favorite levels for the different compilers, such as Sun CC, aCC (HPUX ?), Visual Studio, intel?  Edit:  I just wanted to point out that I don't use "-Werror" (but I do understand it's utility) on gcc/g++ because, I use:   #warning "this is a note to myself"   in a few places in my code.  Do all the compilers understand the #warning macro? We have the matrix: $$\left[\begin{array}{rrr} 0.8&amp;0&amp;0\\ 0&amp;1.2&amp;0\\ 0&amp;0&amp;1\\\end{array}\right]$$ Finding the eigenvalues and eigenvectors are easy. But finding ${\bf M}^n$ when $n \rightarrow \infty$ is the hard part. Any suggestions? So I'm trying to power 2 of these  together in series. I know that I have to add the voltage of the two lights together and get a resistor that restricts the power to that level. I have a 9V battery and the lights are 3V each. I brand new to all of this, and understand almost nothing, so any help would be appreciated. Can someone help me choose the correct resistor (And how to identify that resistor with the color branding thing) so two of those lights listed above can be wired in series? Thanks! How to extract and install .deb without the command dpkg? I am running Debian jessie stable in order to understand how the .deb package interacts with the system. What is the correct way to extract and install a packge_name.deb without the command dpkg? I unintentionally and stupidly wiped my Clash of Clans game data. I went to Application Manager on my Android and clicked 'Clear data'. (I used this for fixes before and it never started a new game.)   Now, my level 60 or so base has been wiped as if was to start a new game. Have I doomed myself to starting again or is there a way in which I can retrieve my old game save? Maybe by contacting Supercell? I have a snapshot of my base. Earth moves how much under my feet when I jump? If I'm standing at the equator, jump, and land 1 second later, the  Earth does NOT move 1000mph (or .28 miles per second) relative to me,  since my velocity while jumping is also 1000mph.   However, the Earth is moving in a circle (albeit a very large one),  while I, while jumping, am moving in a straight line.   How much do I move relative to my starting point because of this? I  realize it will be a miniscule amount, and not noticeable in practise,  but I'd be interested in the theoretical answer. Every once in a while I see users having issues to update due to errors like this:  E:Type 'ain' is not known on line 1 in source list /etc/apt/sources.list.d/some-ppa.list'   with varying types/line numbers/source list files (often after removing a PPA).  How can such an error be fixed? \documentclass{article} \usepackage[style=authoryear-icomp,maxbibnames=9,maxcitenames=2,backend=biber]{biblatex} \usepackage{filecontents} \begin{filecontents}{\jobname.bib} @misc{ABC01,   author = {Author, A. and Buthor, B. and C},   year = {2001},   title = {Alpha}, } \end{filecontents} \addbibresource{\jobname.bib} \begin{document}  According to \textcite{ABC01}, parallel...  \printbibliography \end{document}   Outcome:  According to Author et al. (2001), parallel...    How to get:  According to Author et al.'s studies (2001), parallel... My iPad mini retina is out of warranty,  I forgot to plug in my iPad after the critical battery warning and it went some minutes following the warning. I was not worried because same thing had happened a few times before and iPad was perfectly okay after charging it. However, this time I remember seeing a flash of blue screen immediately after it went black. Then, I plugged it in an waited for a while and tried starting it. Ever since, it fails to start hanging on the apple logo with white background screen.   I tried to connect to my Mac but nothing showed up in iTunes. I am worried now. Can I troubleshoot this or is it broken and needing repair? Bibliography per chapter with continuous numbering I would like to create a document with two chapters. After the first chapter there should be a bibliography. The next chapter should be able to reference items of the former chapter, but only show the new items in its bibliography, starting with the next number from the first bibliography.  Example:     Chapter 1 - The Fu   Fu has been done by Bar [1]. Early versions ...   Bibliography   [1] Bar et. al., Doning the Fu      Chapter 2 - Compining Fu with Herp   Doning Fu as described in [1]   neglects the advantages of Herp pointed out by Derp [2].   Consequently ....   Bibliography   [2] Derp et. al., The Advantages of Using Herp   Please not too much discussion about if that is a friendly-to-use idea, it is not my own demand :) Different behaviour for list.__iadd__ and list.__add__ This question is about the net speed.  I'm from China, and I find that opening pages on Stack Overflow is very fast, normally within a range of 1 to 4 seconds. This speed is very good for a website outside China; it's even faster than some native websites.  Not every website outside China has such good speed, so I am wondering why and how Stack Overflow manages to be so quick. File issues after importing Drupal site I recently tried to move my Drupal site to a new server using this page: . But now the style doesn't seem be loaded and more importantly I get this error on every page in the site (even on the frontpage):  Warning: file_put_contents(temporary://filef76T9k): failed to open stream: &quot;DrupalTemporaryStreamWrapper::stream_open&quot; call failed in file_unmanaged_save_data() (line 1900 of /Library/Server/Web/Data/Sites/Default/drupal/includes/file.inc). The file could not be created.  Any ideas what this could be about? Create a book cover with spine, rear page and flaps