How to write a generic print for vector of vectors using c++
Why can templates only be implemented in the header file?
Do gravitons interact with each other? I always thought the non-linearity of Einsteins field equations implies that there should be direct graviton-graviton interactions. But I stumbled upon  which argues:     If gravitons exist, then, like photons and unlike gluons, gravitons do   not interact with other particles of their kind. That is, gravitons   carry the force of gravitation but are not affected by it. This is   apparent due to gravity being the only thing which escapes from black   holes, in addition to having an infinite range and traveling in   straight lines, similarly to electromagnetism.   Is Wikipedia correct? If not, why not? And what then are the arguments that there must be graviton-graviton interactions?    (As of this question being asked, the above paragraph has been removed from Wikipedia.) How to prevent my screens from turning off, when the screen is locked? I would like to have my screen fully powered at all times, but it goes to standby once I lock my PC. What is a "double date"? The meaning of imaginary time What is imaginary (or complex) time? I was reading about Hawking's wave function of the universe and this topic came up. If imaginary mass and similar imaginary quantities do not make sense in physics, why should imaginary (or complex) time make sense?    By imaginary I mean a multiple of $i$, and by complex I mean having a real and an imaginary part, i.e., $\alpha + i\beta$, where $\alpha, \beta \in {\mathbb R}$. How to use an optimization solver to get t-stats and p-values for the estimates? If there are injective homomorphisms between two groups in both directions, are they isomorphic? If I have two groups, $G$ and $H$ and two injective homomorphisms $\phi:G \to H$ and $\psi: H \to G$, then by the first isomorphism theorem applied to $\phi$, we have that $G \cong \mathrm{Im} (\phi)$, a subgroup of $H$. Similarly, $H$ is isomorphic to a subgroup of $G$. For finite groups, this guarantees that $G \cong H$ but does this hold for infinite groups?  Weird things can happen for infinite groups, e.g $n\mathbb Z \subsetneq \mathbb Z$ but $n \mathbb Z \cong \mathbb Z$. I'm wondering if this kind of thing stops an isomorphism from occurring.  I think this question generalises to rings, modules, fields and so on. Can this be answered for all of these structures? made me think about the movie versions of the 7th book.  In Deathly Hallows Part II      Voldemort has Nagini attack Snape because Voldy thinks that Snape has the Elder Wand's allegiance. We know that Snape didn't actually have the allegiance, Draco did (and by then Harry did) and his plan had failed.   But if Voldy's plan had succeeded with Snape, would he have gotten allegiance?      Since voldemort didn't kill Snape, Nagini did... Induction proof: $S$ contains powers of 2 and predecessors implies $S={\bf N}$ Let $S$ be a subset of $\mathbb{N}$ such that $$2^k\in S\quad\forall\ k\in\mathbb N$$ and, $$k\in S\Rightarrow k-1\in S\quad\forall\ k\ge2,k\in\mathbb N$$  Show by induction that $S=\mathbb N$. OR operator in C not working Error: mysqli_stmt::bind_param(): Number of elements in type definition string doesn't match number of bind variables Prove the inequality $\,\frac{1}{\sqrt{1}+ \sqrt{3}} +\frac{1}{\sqrt{5}+ \sqrt{7} }+\ldots+\frac{1}{\sqrt{9997}+\sqrt{9999}}\gt 24$ Prove the inequality $$\frac{1}{\sqrt{1}+ \sqrt{3}}  +\frac{1}{\sqrt{5}+ \sqrt{7} }+......... +\frac{1}{\sqrt{9997}+\sqrt{9999}} &gt; 24$$   My work:   Rationalizing the denominator gives   $$\frac{\sqrt{3}-1}{2}  +\frac{\sqrt{7}-\sqrt{5}}{2}+......+\frac{\sqrt{9999}-\sqrt{9997}}{2} .$$  Now by taking two as common and separating the positive and negative terms gives  $$\frac{1}{2} [ \{\sqrt{3} +\sqrt{7}+\dots +\sqrt{9999}\} - \{1+\sqrt{5} +\dots+\sqrt{9997}\}].$$  Can we do like this please suggest. Thanks. When will data.SE get updated data? promised that data.SE would &quot;soon&quot; get live data:     I realize it's a long weekend, but given that data.SE is now over 2 months out of date, it would be nice if this was finally rolled out. I have a shapefile with contours and their heights.   Is it possible to make a DEM from contours in QGIS without using GRASS?   I found  but the answer is for ArcGIS Desktop. E: Malformed entry 54 in list file /etc/apt/sources.list (Component) How do you prevent web pages from appearing in the Google search index? I have some web pages that Google has indexed. I have now added a robots.txt file to exclude them, but should I also add a noindex tag? If so, then how do I do so? Is there any explanation for why the other 2 schools in the TriWizard tournament are both single-gender, unlike Hogwarts?  Was single-gender education normal in wizarding world with Hogwarts being the exception?  Was this some special intentional literary trick on Rowling's part or on movie creators'?    Here's the evidence from the movies:  Durmstrang Institute is boys-only:    Beauxbatons Academy of Magic seems to be an all-girl school: MySQL: Allow both remote AND local connections GeoReference tiff image into the Google map? I want to Geo-reference a tiff image contain a Map for a specific region, I need to add this region(image) and Geo-reference it on the Google map, SO I can see on the map for the region I select the image which I have inserted.  the image also need information such as the Latitude and Longitude of corners and size, and the pixel per meter measurement.  How to do the correct Geo-reference for that ? I have 2 partitions (Windows and Ubuntu 13.04) and I am asked which one to boot each time I turn on my computer.  I want to install Ubuntu 13.10 to the entire disk.  I do not mind if all previous Ubuntu/Win data are lost.  How can I do that? I am trying to modify output in my twig file. In D7, I was able modify data in my array with this  check_markup($tweet-&gt;text, 'full_html');   and I see that this function still exists in D8. However, I'm not sure how I would use this in a filter in twig. This is what I have so far:  {% for tweet in params.tweets %} &lt;div class="tweet-wrapper"&gt; &lt;div class="tweet-profile-image"&gt;     &lt;img src='{{ tweet.user.profile_image_url }}'/&gt; &lt;/div&gt; &lt;div class='tweet-text'&gt;     &lt;!--check_markup($tweet-&gt;text, 'full_html');--&gt;     {{ tweet.text }} &lt;/div&gt;   &lt;/div&gt; {% endfor %}   I actually tried to do this before I sent it to the template as well, but it didn't change anything:   foreach($tweets as $tweet) {   $tweet-&gt;text = check_markup($tweet-&gt;text, 'full_html');   $cleanTweets[] = $tweet; } dpm($tweets); $params = array('tweets' =&gt; $cleanTweets); $tweet_template = array('#theme' =&gt; 'twitter_pull_tweet_listing', '#params' =&gt; $params); return $tweet_template;   What I'm trying to do here is make drupal create links for web links in the twitter tweet text. This worked fine for me in D7.