How to search the topics in Stackoverflow by filtering with 2 tags. For Example , I was able to search the questions with single tag like playframework, but if i want to search with tags like playframework, scala, internalization etc,  Can you please suggest me? It will be helpful to me in learning the concepts from stackoverflow
How do I search for questions with specific tags?       For more information about searching, see &quot;&quot; in the .
Are antiparticles just particle-shaped holes? If particles are simply regions of space where certain quantum fields have non-zero divergence, are anti-particles simply the corresponding regions of opposite divergence?    This seems like the intuitive answer, especially when considering the process of annihilation.  I have heard before that anti-particles are analogous to particles moving through time in reverse, which seems to indicate that an annihilation event is just a point of symmetry in that (arguably, single) particle's history.  This analogy breaks down, however, when it comes to gravitation, since there seems to be no evidence of a negative-mass particle.    So what then is the meaning of an anti-particle, when their symmetry is preserved across certain fields, but not other? I go to change my birthdate on Roblox, but nothing shows up, the dropdowns are just blank with no Month, Day or Year:  It also shows me a pop up asking to put in the Missing Details to improve the experience, but no matter how many times I put in my age it doesn't save and asks it again. Sharing Test code in Maven Show that if $g \circ f$ is injective, then so is $f$. The Problem:  Let $X, Y, Z$ be sets and $f: X \to Y, g:Y \to Z$ be functions.  (a) Show that if $g \circ f$ is injective, then so is $f$.  (b) If $g \circ f$ is surjective, must $g$ be surjective?  Where I Am:  So, I really have trouble with these, for some reason. I can draw pictures and make sense of the problems, but writing down proofs is very difficult for me.   Basically, for (a), I ended up with some complicated statement involving an implication implying another implication and then tried to derive a contradiction. It just got so convoluted that I couldn't make sense of it anymore, and I know there's a quick, elegant way to show it.  For (b), I know that $g$ need not be surjective. Once again, though, proving it directly from definitions has given me a bit of a headache.  Any help here would be appreciated. Thanks in advance.  The Proofs!  Ok, I did it. Thanks for the help, everyone! Let me know if there's anything wrong with these proofs, or if they could bet any better.  (a) Suppose $f$ is not injective. Then $$ f(x_1)=f(x_2) \implies x_1 \ne x_2 \text{        }(*).$$ Let $f(x_1)=y_0=f(x_2)$ and let $g(y_0)=z_0$. Then $$ (g \circ f)(x_1) = (g \circ f)(x_2) = g(y_0) = z_0. $$ Since $g \circ f$ is injective, $$ (g \circ f)(x_1) = (g \circ f_2) \implies x_1 = x_2. $$ However, this contradicts $(*)$. Therefore, $f$ must be injective.  (b) Suppose $g$ is not surjective. Then  $$ \forall y \in Y, \exists z \in Z \text{ such that } g(y) \ne z \text{         }(**).$$  Since, $g \circ f$ is surjective,  $$ \forall z \in Z, \exists x \in X \text{ such that } g(f(x)) = z \text{       } (***). $$  Let $f(x) = y$. Then,  $$ g(f(x)) = g(y) = z. $$  Because of $(***)$, this is true for all $z \in Z$, which contradicts $(**)$. Therefore, $g$ must be surjective. Where can I get images for commercial use? I am running a web site design service for local small business owner. I want avoid legal issues on the images I use. Usually, the images found on Flickr are forbidden for commercial use. Where would be a normal channel to get pictures for commercial use with minimal cost? How can I validate that the picture I used has no legal risk? I was surprised recently to find that it's possible to have a return statement in a finally block in Java.  It seems like lots of people think it's a bad thing to do as described in ''. Scratching a little deeper, I also found '' which shows some pretty horrible examples of other types of flow control in finally blocks.  So, my question is, can anyone give me an example where a return statement (or other flow control) in a finally block produces better / more readable code? Irreducible polynomial in field extension I have this problem      Let $L/K$ be a finite field extension and $|L:K|=m$. Let $f(x)$ be an irreducible polynomial of degree $n$ in $K[x]$ and $\gcd(m,n)=1$. Prove that $f$ is irreducible over $L$.   I'm just a beginner so I'm really confused with the $\gcd(m,n)=1$, I don't know how to use it. So help me with this problem. Thank you Pass php variables to js without drupal behaviour I stand on the following tricky situation:  I have a node with geofield coordinates attached. I am constructing an array of points. Something like:  Array ( [86] =&gt; Array     (         [0] =&gt; Array             (                 [lat] =&gt; 39.1641410477                 [lon] =&gt; -2.633972168             )          [1] =&gt; Array             (                 [lat] =&gt; 41.0420738489                 [lon] =&gt; -2.633972168             )          [2] =&gt; Array             (                 [lat] =&gt; 41.0420738489                 [lon] =&gt; 1.2524414063             )          [3] =&gt; Array             (                 [lat] =&gt; 39.1641410477                 [lon] =&gt; 1.2524414063             )         [4] =&gt; Array             (                 [lat] =&gt; 39.1641410477                 [lon] =&gt; -2.633972168             )     )  [85] =&gt; Array     (         [0] =&gt; Array             (                 [lat] =&gt; 39.1641410477                 [lon] =&gt; -2.633972168             )          [1] =&gt; Array             (                 [lat] =&gt; 41.0420738489                 [lon] =&gt; -2.633972168             )          [2] =&gt; Array             (                 [lat] =&gt; 41.0420738489                 [lon] =&gt; 1.2524414063             )          [3] =&gt; Array             (                 [lat] =&gt; 39.1641410477                 [lon] =&gt; 1.2524414063             )         [4] =&gt; Array             (                 [lat] =&gt; 39.1641410477                 [lon] =&gt; -2.633972168             )     ) )   I want to pass this to my-googlemaps.js in order to be used by google's init map Google map is defined as:  my-map:   header: true js:   js/my-googlemaps.js: { }   https://maps.googleapis.com/maps/api/js?key=my_key&amp;callback=initMap: {type: external, attributes: {defer: true,async: true}} dependencies:   - core/drupal   - core/drupalSettings  my-googlemaps.js:   console.log(Drupal.settings);   function initMap() {}   This way I get Drupal.settings undefined, which makes sense I guess. On the other hanve if I place initMap into a behavior It can not be seen as a callback as defined in googleapis.com before.  Has anyone stumbled with this before? Any idea how to attack the problem? This problem is bugging me for some time.     $f:(X,\mathcal{T}) \to (Y,\mathcal{T}')$ is a continuous bijection where $(X,\mathcal{T})$ is compact and $(Y,\mathcal{T}')$ is $T_2$ (i.e. Hausdorff and $T_1$). Then show that $f$ must be a homeomorphism.   So far I have failed to understand any relation between the compactness of domain and $T_2$-ness of the range. I tried in vain to prove that $f(U)$ is open in $(Y,\mathcal{T}')$ whenever $U$ is so in $(X,\mathcal{T})$. I know $f$ makes $X$ and $Y$ respectively $T_2$ and compact and hence makes both of them $T_4$ spaces. But that is not coming to any use. I would be glad if someone helps me with a solution. Thank you. UK coastline shapefile? What is the most convenient way to read definitions of in-memory symbols when we don't have the source files? (Spelunking tools) Why are the two versions of Chromium and VLC available in Ubuntu software of different sizes? "This question has been asked at Stack Overflow" vs. "on Stack Overflow" How should I phrase it:     This question has been asked at Stack&nbsp;Overflow.   Or,     This question has been asked on Stack&nbsp;Overflow. When does $120$ divide $n^5 - n$ Find n such that $n^5 - n$ is divisible by $120$. (*Here $n$ belongs to the natural number set)  Seems a trivial problem, but the answer mentioned in the text book seemed incomplete to me so I'm here just to ensure whether approach to this problem is correct or not.  So my approach is as follows: We know that $n^5 - n$ can be written as $n^5-n = n(n-1)(n+1)(n^2 + 1)$  Now since it's product of three consecutive natural numbers so it's divisible by $3! = 6$. Now using Fermat's Little theorem we can prove that $n^5= n \mod5$ hence $n^5 - n$ is divisible by $5$ as well. So $n^5 - n$ is divisible by $30$. Now to ensure their is another factor of $4$ in the term we need to ensure that $n^5 - n$ is divisible by $8$. I found that all odd natural numbers and multiples of $8$ makes $n^5 - n$ divisible by $8$, hence $n^5 - n$ is divisible by $120$. But in the text book they have only mentioned odd natural numbers as answer, which seemed incomplete to me.  Thanking everyone in advance:P can anyone help me with this, I got stuck on it.  let $a_n$ and $b_n$ (for $n$ a non-negative integer) be two sequences of real numbers such that $\lim_{n\to \infty}a_n=a$ and $\lim_{n\to \infty}b_n=b$. prove that $\lim_{n\to \infty} \frac{a_0b_n+a_1b_{n-1}+....+a_nb_0}{n}=ab$. When voting to migrate an off-topic question, why is the list of sites limited? When and why will a compiler initialise memory to 0xCD, 0xDD, etc. on malloc/free/new/delete? I know that the compiler will sometimes initialize memory with certain patterns such as 0xCD and 0xDD.  What I want to know is when and why this happens.  When  Is this specific to the compiler used?  Do malloc/new and free/delete work in the same way with regard to this?  Is it platform specific?  Will it occur on other operating systems, such as Linux or VxWorks?  Why  My understanding is this only occurs in Win32 debug configuration, and it is used to detect memory overruns and to help the compiler catch exceptions.  Can you give any practical examples as to how this initialization is useful?  I remember reading something (maybe in Code Complete 2) saying that it is good to initialize memory to a known pattern when allocating it, and certain patterns will trigger interrupts in Win32 which will result in exceptions showing in the debugger.  How portable is this? My friend wants to consolidate his various retirement account accumulated over the past 20-30 years to make it easier to manage/track his retirement savings. He doesn't recall immediately all the accounts he currently has (one of the reasons to rollover), but we've determined he has at least the following types of accounts: 401(a), 401(k), 403(b), 457(b), and "something from the city". He's trying to track down all the relevant paperwork for all of the accounts, but we'd like to know what kind of limits he might have to watch out for.   Are there any restrictions on the types of the accounts that can be rolled over? Is there a limit to the number of accounts that can be rolled into a single IRA (whether all at once or over the lifetime of the IRA)? Is there a limit to the number of times accounts can be rolled over (can/should he do 1 or 2 at a time as he gets the paperwork in order, or wait until he has everything sorted out)? Is this a yearly limit or lifetime? Is there a dollar limit on the amount that can be rolled over? Is there a limit to the age of accounts that can be rolled over?   As far as we know, all of the accounts are pre-tax/non-Roth accounts, and that Roth vs. traditional accounts should be rolled over to separate (Roth vs. traditional) IRAs. Why do I sometimes see a downloading 'pie' icon when viewing photostream photos? it normally shows in the bottom corner as a sort of 'pie' that fills up as the picture is downloaded, similar to the 'app downloading' pie when viewing a downloading app on the home page/s  prior to this the picture resolution is terrible Return a value when using jQuery.each()?