Verifying Email address
How to validate an email address in JavaScript
Prime ideal and nilpotent elements Tags on badge question list I'm trying to get the Weed-Eater hat on Stack Overflow. To do so, I'm looking at the list of questions . The problem is, no tags show up there, and so it's rather difficult to see which ones I have a shot at. Any chance of showing the tags on this page?  I realize that getting this before Winter Bash is over would be difficult, but it would be good to keep such things in mind for the future. How to perform a true GIS clip of polygons layer using a polygon layer in R? I would like to do a true GIS Clip in R of soils polygons using a series of single boundary polygons, but I cannot find an R function to properly do it. It should work just like the clip function in ESRI's ArcMap. I've tried the over method in sp package but it doesn't seem to work for polys over polys.   One suggestion was to use the gIntersection in rgeos package as a clip using the following code:  #------------------------------------ library(rgeos) library(maptools)  #Read layers as SpatialPolygonsDataFrame (both the same Albers projection) Soils_poly = readShapePoly("Soils_polygons")  #Note - Has 400 polygons clipper_poly = readShapePoly("clipper_polygon")  #Note - Has 1 polygon  #Try gintersection as clip  Clipped_polys = gIntersection(Clipper_Tile_poly, Soils_poly)  #-----------------------------------   This takes 5 minutes to run (way too slow) and errors with this:     Error in RGEOSBinTopoFunc(spgeom1, spgeom2, byid, id, drop_not_poly, "rgeos_intersection") :      TopologyException: no outgoing dirEdge found at -721459.77681285271 2009506.5980877089   I also tried this code to check for overlap:  gIntersects(Clipper_Tile_poly, Soils_poly)   and the result was TRUE. clip function in ESRI ArcMap works fine for this data.   Anyone knows of an R function to properly do a clip on spatial polygons using spatial polygons? When I go to any github.com page in Chrome, I get a big ugly error:  You attempted to reach github.com, but the server presented a certificate issued by an entity that is not trusted by your computer's operating system. This may mean that the server has generated its own security credentials, which Chrome cannot rely on for identity information, or an attacker may be trying to intercept your communications. You cannot proceed because the website operator has requested heightened security for this domain.  The same thing happens (in Chrome and with curl) when I go to  too. This strange problem started about a week and a half ago. Here's what I see when I click the broken lock icon in the address bar:   But gist.github.com works just fine:   It doesn't work with curl either:  Everything works fine in Firefox. How can I fix my root CA problem? Here's what it looks like in Firefox:   Update: I noticed that the first certificate in the chain is different in my broken Chrome/Safari as compared to Chrome on my other computer.   (There's no nasty red X anymore because I trusted it in Safari.) See how the issuers are different? What can I make of that? Blender 2.80 AV Sync missing? I just installed Blender 2.8 and for the life of me I can not find AV Sync anywhere and video editing has become impossible. Is there some new setting I am unaware of? $A$ and $B$ are $n\times n$ matrices and $A+B=AB$. I have an interesting proof that this implies $A$ commutes with $B$, but the proof only works when $||B|| \lt 1$. I'm looking for a way to salvage the proof so that it works for all $B$.  $$A=AB-B$$ $$A=(A-I)B$$ by repeatedly substituting $A$ with $(A-I)B$ on the RHS, $$A= (A-I)B^N - \sum_{i=1} ^{N-1} B^i$$  Since the space of $n\times n$ matrices is Banach (hence complete) under the standard operator norm, the limit $\sum_{i=1}^{\infty}B^i$ is well defined given $||B|| \lt 1$. Hence, taking the limit as $N \rightarrow \infty$, $$A =  -\sum_{i=1}^{\infty}B^i$$  Now the LHS commutes with B, hence so does the RHS.    Is there some trick to extend the method to work with any $B$ where $||B|| \geq 1$? I know that the result is true due to another simple algebraic proof, but I'd like to see if this method can be salvaged. I was told that the following does not work:     Employees having children will be granted a day off.   However, this sounds better:     Having children, those employees will be granted a day off.   What is wrong with the first clause? Emboss text onto curved surface I am fairly new to blender and I am trying to do something which I am assuming is fairly straight forward with no success. All I'm looking to do is emboss some text onto the curved part of a yogurt pot. Image attached below. What is the quickest and easiest way of doing this?  Thanks in advance Use of *args and **kwargs Preventing robots from crawling specific part of a page As a webmaster in charge of a tiny site that has a forum, I regularly receive complains from users that both the internal search engine and that external searches (like when using Google) are totally polluted by my users' signatures (they're using long signatures and that's part of the forum's experience because signatures makes a lot of sense in my forum).  So basically I'm seeing two options as of now:   Rendering the signature as a picture and when a user click on the "signature picture" it gets taken to a page that contains the real signature (with the links in the signature etc.) and that page is set as being non-crawlable by search engine spiders).  This would consume some bandwidth and need some work (because I'd need an HTML renderer producing the picture etc.) but obviously it would solve the issue (there are tiny gotchas in that the signature wouldn't respect the font/color scheme of the users but my users are very creative with their signatures anyway, using custom fonts/colors/size etc. so it's not that much of an issue). Marking every part of the webpage that contains a signature as being non-crawlable.   However I'm not sure about the later: is this something that can be done?  Can you just mark specific parts of a webpage as being non-crawlable? Proving that $\left( \frac{\partial^2}{\partial x^2} + \frac{\partial^2}{\partial y^2} \right) \lvert f(z) \rvert^2 = 4 \lvert f'(z) \rvert^2$ Given $f$ entire show that $$ \left( \frac{\partial^2}{\partial x^2} + \frac{\partial^2}{\partial y^2} \right) \lvert f(z) \rvert^2 = 4 \lvert f'(z) \rvert^2 $$ I've come close to getting the exact answer by writing $f(z)$ as $u(x,y)+iv(x,y)$ and realizing the Laplacian of f is equal to zero. This leads to a lot of cancellations but I'm still making mistakes in my computations and I can't figure out where. Any help is appreciated. How to create meaningful relationships with NPCs How do I help the PCs to create meaningful relationships with NPCs?   Maybe it is a result of my group playing too many one-dimensional adventures trying to find whatever MacGuffin they are after each week, but most of the time my PCs don't tend to value NPCs too much. Every time they meet an NPC they quickly evaluate what immediate values the NPC can give or tend to ignore them.  What I would really like is to have some good relationships where the PCs actually go out of their way to help NPCs without selfish motivation or even just to try to think of NPCs more and how their actions affect others.  I am not looking for a specific game rules solution to this, but instead techniques to get the players to feel attachment to these fictional characters. Granting access only to standby database One of the physical standby databases in my environment is open in read-only mode and used for reporting purposes . I want to give users access only to this particular standby, not to primary db.   The best approach I found so far is to create AFTER LOGON ON DATABASE trigger which checks v$instance (or maybe v$database), and throws error for depends on  values of host_name/instance_role columns  .   I wonder if there is a better way to do it. General way to determine $\mathbb{Q}(\gamma) = \mathbb{Q}(\alpha,\beta)$ given $\alpha$ and $\beta$ Does registering [name]overflow.com violate Stack Overflow's trademark? what operation repeated $n$ times results in the addition operator? Is "architect" a verb and a noun? I hear the word architect used as a verb in the technical field and now more often in other industries and groups, for example:     We need to architect a better solution to the problem.   I am interested if this is considered acceptable usage, as I see this word being used more in published technical documents (not necessarily books, but corporate publications).  I can see how a conductor can conduct, a typist can type, but can a scientist "science"?  A scientist might research, analyze, and so forth, as an architect might design, create, build, etc.  Merriam-Webster , however, I have been told that other dictionaries exist that define architect as both a noun and a verb&nbsp;— is there a credible reference or source that authoritatively answers this question? Why is TV remote's infrared wave shown by a camera as purple light, why not red or something else? Time travel film: character with male and female reproductive organs is taken back in time by a barman who turns out to be themselves I have had a friend give me a rough description of a film and I'm curious to find out what it actually is. I don't know very much. I understand this will be difficult, especially since every time my friend explains the tale it's different so this description is likely to contain some inaccuracies.  The film's plot begins with a recounting given by the main character, who had both male and female reproductive organs but had one set removed (not sure which, think male ones were removed). The main character is narrating this tale to the barman in a bar. The barman then takes the main character back in time, where they make love to themselves and produce a child.  The child, once born, is abandoned by the mother in the past - but the barman takes the child to the orphanage and leaves them there, ensuring their survival. Eventually it is revealed that the child was the main character themselves, and so was the barman.  In other words every major character introduced up to that point was the same person who had severely messed with their own timeline. Replacing strings in files based on certain search criteria is a very common task. How can I    replace string foo with bar in all files in the current directory? do the same recursively for sub directories? replace only if the file name matches another string? replace only if the string is found in a certain context? replace if the string is on a certain line number? replace multiple strings with the same replacement replace multiple strings with different replacements