In Javascript  parseInt(null) returns a NaN parseNumber(null) also returns a NaN    isNaN('abcd') returns true, as 'abcd' is of course not a number, isNaN(5) returns false    but strangely    isNaN(null) returns false, which is odd as implies it is a number, but as we saw in the parseNumber it was seen by that as NaN  There appears to be an inconsistency between the way null is viewed by parseInt and by isNaN one sees it as NaN and the other sees it as a Number. Why are they inconsistent?
This code in JS gives me a popup saying "i think null is a number", which I find slightly disturbing. What am I missing?    if (isNaN(null)) {   alert("null is not a number"); } else {   alert("i think null is a number"); }     I'm using Firefox 3. Is that a browser bug?  Other tests:    console.log(null == NaN);   // false console.log(isNaN("text")); // true console.log(NaN == "text"); // false     So, the problem seems not to be an exact comparison with NaN?  Edit: Now the question has been answered, I have cleaned up my post to have a better version for the archive. However, this renders some comments and even some answers a little incomprehensible. Don't blame their authors. Among the things I changed was:   Removed a note saying that I had screwed up the headline in the first place by reverting its meaning Earlier answers showed that I didn't state clearly enough why I thought the behaviour was weird, so I added the examples that check a string and do a manual comparison.
What do wizard children do before attending Hogwarts? Most of the wand-carriers that come from a non-Muggle family seem fairly uneducated when it comes to interacting with Muggles.  This implies that they don't go to any type of Muggle school before entering into their education at Hogwarts (or whichever Wizarding school they go to), or else they would at least understand some Muggle culture.  What do children from magical families do before going to Hogwarts if they don't go to a traditional school?  Is there any evidence that they're homeschooled? I'd really like your help proving:  $(A\rightarrow B),(A\rightarrow C)\rightarrow B,  \mapsto_{HPC} B $  Where $HPC$ is the Hilbert's system proof which contains the following relevant axioms:   $A\rightarrow(B \rightarrow A)$ $(A\rightarrow(B\rightarrow C)) \to ((A\rightarrow B)\rightarrow(A\rightarrow C))$ $(A\rightarrow B)\rightarrow ((A\rightarrow\bar{B})\rightarrow \bar{A})$ $\bar{\bar{A}} \rightarrow A$   In addition tried to use these following lemmas: $\bar{A} \rightarrow (A \rightarrow C) $ and $(A\rightarrow B)\rightarrow (\bar{B} \rightarrow \bar{A})$.  Any suggestions? Cyrillic monospaced font in XeLaTeX I've installed full TexLive 2011 using "install-tl" script in Ubuntu 12.04.  When I was using TexLive 2009 from repositories the following file was compiled without any errors.  \documentclass{article} % XeLaTeX \usepackage{xltxtra} \usepackage{xunicode}  % Fonts \setmainfont{Arial} \newfontfamily\cyrillicfont{Arial} \setmonofont{Courier New}  % Lang \usepackage{polyglossia} \setmainlanguage{russian} \setotherlanguage{english}  \begin{document} English normal.  \texttt{English monospace}.  Русский обычный.  \texttt{Русский моноширинный}.  % Text in Russian \end{document}   But XeLaTeX from TexLive 2011 gives this error:     ERROR: Package polyglossia Error:       --- TeX said ---   The current roman font does not contain the Cyrillic script!   Please define \cyrillicfont with \newfontfamily.      See the polyglossia package documentation for explanation.   Type  H   for immediate help.    ...                                                    l.17 ...nglish normal.  \texttt{English monospace}                                                     .   In spite of this error the output PDF is correct.  The error remains if comment out \setmonofont{Courier New}.  Using Courier New as main font gives no error on normal text (without \texttt, \textbf and so on).  Using DejaVu Sans Mono as monospaced font gives no error too.  I've been searching for solution few hours but there aren't any.  Maybe this is a bug in Polyglossia or Fontspec? Google Sheets has several import functions   IMPORTDATA IMPORTFEED IMPORTHTML IMPORTXML   Sometimes the above functions returns errors like #N/A Imported content is empty and would like to be sure that there isn't a problem with the resource content to be imported.  How do I know if these functions are able to get the content that I looking to import?  I know that there also exist IMPORTRANGE but that function only is able to import content from Google Sheets spreadsheets What are bitwise shift (bit-shift) operators and how do they work? I've been attempting to learn C in my spare time, and other languages (C#, Java, etc.) have the same concept (and often the same operators) ...   What I'm wondering is, at a core level, what does bit-shifting (&lt;&lt;, &gt;&gt;, &gt;&gt;&gt;) do, what problems can it help solve, and what gotchas lurk around the bend? In other words, an absolute beginner's guide to bit shifting in all its goodness. Find the value of $\sum_{k=1}^{n}k\binom{n}{k}$? How to install XAMPP? What does the '!!!' syntax mean in javascript? What is the relationship between Guide Number and flash power level? From this , I understand that the flash guide number (GN) is given by the following formula:  Guide Number = Shooting Distance × f-number ÷ ISO factor   I'm assuming that the GN calculated via the equation above will be based on a flash that is firing at full power. Am I correct to assume that if I set the flash to fire at half power, that the guide number is effectively halved? i.e. the equation will now be:  Guide Number = Shooting Distance × f-number ÷ ISO factor * Power Level   where power level can be the following 1, 1/2, 1/4, 1/8, ... 1/64, etc? How to find the most common name in passwd file Why do Oreo crumbs float to a single glob at the very center in a glass of milk? I had Oreos and milk a while ago and left my half-full cup of milk out on the counter. Afterwards I noticed that the crumbs had surfaced in a circular coin-sized glob, and just now I looked again to see all of the crumbs seem to have compressed into a more dense glob at the very center of the cup.   Why does this happen? Am I going to have trouble flying with a reversed name on the ticket? I'm flying to Peru with my girlfriend next week and I realized that her name is incorrect on the reservation.  Instead of Sally Marie Jones it's Jones Marie Sally.  We're flying into Houston, then Lima, and in Lima we switch airlines for our flight to Cajamarca.  I booked the ticket with Orbitz who made the reservation with United. United booked the flight with LAN air, the Peruvian airline.  Both companies say that they are unable to change the name because of TSA restrictions not allowing a name change. I asked if I could just cancel and re-book, but United said they could not do this because there are multiple airlines involved.  A note has been attached to the reservation explaining the issue, and the United rep said that they would be able to print her boarding pass with the correct name. However, he said there are no guarantees that she'll be able to fly because although the boarding pass will be correct, the ticket will still have the reversed name.  I was prepared to just take the chance that it will all work out, seeing how it's really obvious the name is just backwards, but with recent events I'm worried that US airport security is going to be extra strict for the next little while.  Is this something I need to worry about, or are chances good that this will work out fine?  The United rep said there's a chance we could cancel the United flights and get a new ticket with the correct name for no cost, but we'd have to pay for new tickets within Peru ($500 out of the total $1300 ticket cost). I'd rather not do this unless there's a reasonable chance we'll have trouble at the airport. For me the distinction between sites is purely topical. I get that there's a right and a wrong place to ask questions, but I regularly ask questions across a number of sites. They all log me in (in a weird sort of way), and now there's the global inbox.  I've read that there's a feed  and that there's a  but neither of these are what I want.  What I'd like is to have an RSS feed from my global inbox, i.e. to include notification of updates to my public questions, answers, comments. Is this possible? Why was Sirius ever convicted? Sirius himself says at some point in Goblet of Fire that Crouch pushed through legislation to have him convicted and thrown in Azkaban without a trial.  There seems to be a general consensus, specifically voiced by Fudge but also implicit in Crouch pushing through this legislation, that Sirius was considered one of Voldemort’s innermost, most dangerous, and most trusted right hands. Easily as inner-circle as the Lestranges, for example.  It seems quite unlikely to me that someone so close to Voldemort should not be a Death Eater—apart from Fenrir Greyback (who I would think is much less inner-circle), I do not recall hearing of any of Voldemort’s important servants not being Death Eaters.  As far as canon describes, all Death Eaters have the Dark Mark magic-tattooed on their arm, to be used as a way for Voldemort to summon them to him. Considering that Karkaroff, who had definitely burnt all his Death Eater bridges, still had the Dark Mark, I am assuming that getting rid of the Mark is not possible: once it’s on, it stays on.  Yet, as Hermione points out in Order of the Phoenix (ch. 16, “In the Hog’s Head”), Sirius does not have the Dark Mark.  So why was he so swiftly convicted and locked up? I mean, I know they were eager to be seen to be doing something (as Fudge keeps pointing out is his excuse for most of the miscarriages of justice he commits)… but seriously, did no one think to check if Sirius actually had a Dark Mark on his arm or not? Did the Ministry of Magic not even know at the time that all Death Eaters had the Mark? Or were they just happy to accept—without the scrutiny of a full trial—that a non-Death Eater would commit mass murder for a Voldemort who was presumed defeated? Why are lamps and mesh lights not illuminating anything? There are several techniques to do a 3 point lighting system.   How do you properly light a scene while using mesh planes as emission light sources?   I'm following , however despite setting up planes to act a lighting sources, the scene is still very dark.      Actual Blender file here: Are Variable Operators Possible? How do I create a file of size 10M, format it with ext3 filesystem and then mount it in /media/fuse?  I tried with  mkfs -t ext3 file   then to mount it  mount -t ext3 file /media/fuse   It didn't work because it said that file wasn't a block device. Can anybody help me? I have a fairly modern desktop computer, an AMD Athlon II X2 based silent PC, that does not work.  When turned on, it will start physically (all fans are rotating, disks start up...) but not give a signal on any of the graphics ports (DVI, VGA, and HDMI, I tried all three). Also, the reset button does not seem to have any effect.  I have stripped the mainboard bare of all SATA connections, extension cards, and the one 2GB RAM chip to eliminate them as the problem source, but to no avail, so I think it's fair to assume it's either the mainboard or the processor that are at fault.  However, I have neither a replacement mainboard, nor a replacement processor handy to identify which one is broken. The cause of the defect is unknown, so for all I know, it could be both. Therefore, I'm reluctant to buy replacement hardware blindly before knowing more.   Is there any way to further diagnose (or at least get some indication) which component is broken without buying replacement hardware? Is it possible to experimentally show that observable universe is much larger than ~93B ly? How to make a water vortex I'm very new to Blender and I'm trying to make a water vortex like this.(may be not the easyest first project for a newbie)     I watched several tutorial on liquids particle etc but I'm not sure what is the best aproach. What I tried  until now:   I made a particle system with a vortex force field. It looks good, but I'm not able to add the right material.      I played around with the fluid physics, the water looks good but if I add a vortex force field it does nothing.   I would be very grateful if somebody could point me in the right direction because I'm definitely stocked.