LNK2019 Error at template function of my class
Why can templates only be implemented in the header file?
Why does the natural ring homomorphism induce a surjective group homomorphism of units? I'm trying an old problem here:   Suppose $n\mid m$, and I have a natural ring homomorphism $\varphi\colon \mathbb{Z}/m\mathbb{Z}\to\mathbb{Z}/n\mathbb{Z}$ defined by $\varphi(j)=j\mod{n}$. I can verify that this is a ring homomorphism, but why does it induce a surjective group homomorphism on the unit groups $(\mathbb{Z}/m\mathbb{Z})^\times\to(\mathbb{Z}/n\mathbb{Z})^\times$?  My question in particular is why is it surjective? I take $k\in(\mathbb{Z}/n\mathbb{Z})^\times$. Then there exist integers $s,t$ such that $sn+tk=1$. Since $n\mid m$, I can also write $m=na$. So multiplying through I get $sm+tka=a$. I'm lost here. How can I find a unit in $(\mathbb{Z}/m\mathbb{Z})^\times$ which maps to $k$ to show surjectivity? How to determine the value of a domain name? I'd like to register a second-level domain with the .com extension and I noticed that it has already been registered and the owner put it for sale and let the possibility to make an offer in their site or by contacting them.  I saw that domains are generally sold for extremely different prices, so I'm confused.  Are there any general criteria to decide how much I should offer to purchase a domain? Capitalization of explanation of abbreviations What posts should be escalated to staff using [status-review], and how do I escalate them? What is the difference in meaning of "frustrated at" and "frustrated with" used in sentences like     He is frustrated with me   or      He is frustrated at me   When is each of these sentences above are used? Delete all data for a kind in Google App Engine I would like to wipe out all data for a specific kind in Google App Engine. What is the best way to do this? I wrote a delete script (hack), but since there is so much data is timeout's out after a few hundred records. I know classical physics, quantum mechanics, special relativity, and basic nuclear physics. I would like to get into some particle physics.   Where can I find a good introduction? It might be useful to segment books by whether they require quantum field theory or not. My wife, two kids and I will be traveling in Ireland and the UK Nov. 1st through 21st. We're flying into and out of Dublin. Our plan is to do a clockwise tour: Fly into Dublin -> Belfast -> Scotland -> England/London -> Back to Dublin to fly home.  We've been planning to rent a car when we land in Dublin (doing just things outside Dublin at the start of the trip) and have a car all the way until London, then turn in the car and take a train/ferry to get back to Dublin before flying home.  However, reading through the car rental section of Rick Steve's 2012 Ireland book is causing us to question if this is the right plan.  He says (p. 480):     If your trip covers both Ireland and Great Britain, you're better off   with two separate car rentals, rather than paying for your car to ride   the ferry between the two islands. On an all-Ireland trip, you can   drive your rental car from the Republic of Ireland into Northern   Ireland, but be aware of drop-off charges ($75-150) if you return it   in the North.   So it seems like he recommends against doing one car rental for both islands, but he also recommends against renting in the Republic of Ireland and returning it in Northern Ireland (our other option for our current itinerary).  So we're not sure which is best here.  A few questions about this:   If we do one car rental all the way from Dublin to London, will there be a similar $75-$150 fee? Is there an easy place to return a car on the Northern Ireland side of one of the Northern Ireland -> Scotland ferries, and an easy place on the Scotland side to rent a car?  We'd like to minimize the number of buses/whatever we need to take between car rentals since we'll be lugging around car seats for both of our children (on top of carrying them and our luggage). Will one way be significantly cheaper than the other?  Besides the basic cost of taking the car on the ferry and the drop-off charges, our credit card will cover insurance in Scotland/England but not in Ireland, so we could potentially get a better rental rate by renting a second vehicle once we're on Great Britain. Although, I know you often get a better rate when keeping a car rental for longer, so that may negate any benefit from the credit card covering the insurance. best practices for organizing digital and physical articles As a thirsty graduate student, I've amassed a burgeoning collection of research articles in both paper and digital formats. Right now I manage pdfs and references with Zotero, but I'm still searching for an organization logic for paper documents that allows rapid access and prevents redundant printing and storage.  have suggested organizing by topic, while another approach is to sort by author name. Topical organization has not worked well for me in the past because my research is highly interdisciplinary, confounding my categorization efforts. For a coupled digital-physical organization system I'm considering the following:   Digital documents and references stored and tagged in Zotero Indicator in Zotero whether or not I've printed in the file Physical documents stored in manila file folders labelled alphabetically   What is the most effective way that you've found to maintain both paper and digital document repositories? If the dual spaces are isometrically isomorphic are the spaces isomorphic? For regression problem, I have seen people use "coefficient of determination" (a.k.a R squared)  to perform model selection, e.g., finding the appropriate penalty coefficient for regularization.   However, it is also common to use "mean squared error" or "root mean squared error" as a measure of regression accuracy.  So what is the main difference between these two? Could they be used interchangeably for "regularization" and "regression" tasks?  And what are the main usage of each in practice, such as in machine learning, data mining tasks? If I build a package from source how can I uninstall or remove completely? I used source code to build one package such as below:  ./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var --libexecdir=/usr/lib --with-package-name="Myplugin" --with-package-origin="http://www.ubuntu.org/" --enable-gtk-doc --disable-static make make install   But unfortunately, i discovered that its the latest version, and has lot of bugs, so i need to remove it/uninstall it. But how can i do so? I tried make clean; make uninstall but still i see it exist:  # pkg-config --list-all | grep Myplugin myplugin-.... $ ls /usr/lib/myplugin/libXYZ.so exist....   How do you remove this now? Dynamic SELECT TOP @var In SQL Server How can I have a dynamic variable setting the amount of rows to return in SQL Server? Below is not valid syntax in SQL Server 2005+:  DECLARE @count int SET @count = 20  SELECT TOP @count * FROM SomeTable writing js objects to files (including methods) in nodejs? I have my own AppleID ("Bob") but I don't use this email addy "Bob" anymore. I want to add my current, daily used email addy ("Jim") to my ID, or better yet, make it my only AppleID and delete "Bob". BUT... I already used "Jim" for an AppleID for an older friend who had no email address, so set it up for him on mine, "Jim".  My older friend now has an email address ("Ivan") so can I   add "Ivan" to his AppleID, make it the primary email address, and then delete "Jim" from it? Or... delete his AppleID and create a new one for him "Ivan" knowing he would lose his minor purchases   And most importantly, this would all be pointless unless: - will deleting/removing "Jim" as linked to my friend's AppleID then make "Jim" available for me and no longer registered to another account? Here is a problem which i have not been able to do for quite sometime.   For $n \geq 2$, show that $n \nmid 2^{n}-1$.   I have thought of proving this in two ways: One by using induction which didn't actually work. Next by Fermat's little theorem we have $2^{p-1} \equiv 1 \ (\text{mod} \ p)$, which actually says that for $p \mid 2^{p}-2$. But i couldn't proceed more than this. Any ideas by which i can actually solve the problem? convexity proof of a function including ln and sums Render every Nth frame of an animation I want to render every Nth frame of an animation, in this case every 12th frame. This way I can play back the animation at 2fps and see if everything is going correctly.  I'm a real novice with Blender Python and cobbled this together:  import bpy  for f in range(startframe,endframe,NthFrame):     bpy.context.scene.frame_current = f     bpy.ops.render.render()     bpy.data.images['Render Result'].save_render(filepath="" + str(f) + '.png')    This kind of works, the right images are rendered and saved. However it completely freezes up Blender, and after about an hour it crashes on windows due to being unresponsive I guess. How can I fix this? Preferably I'd like it to work like rendering an animation normally works, i.e. being able to still use Blender and seeing the progress of each rendered frame. What should I look for when buying chain lube / lubricant? In the past, I personally have only used WD-40.   However, I have occasionally had my bicycle looked over at the locally run, free service sessions and most of the mechanics there use a hand applied type of greasy gel (I forget the name).  Questions:   Is WD-40 suitable for bicycle chains? Would alternatives provide better chain longevity? When shopping around for lubricant, what are the most important things to look for? What do you use and why?  (optional added extra) Any tips for reducing chain wear? What blueprints become available during story? As I progress, I realize that some blueprints open up throughout the story and don't have to be researched. Are these random or are they always the same and is there a list over those? Seems you can easily waste research point if you don't know that.