C++ Constructor without new
What are uses of the C++ construct "placement new"?
What is $\Delta t$ in the time-energy uncertainty principle? The camera in Far Cry 3 is useful for tagging enemies from a distance but also includes the ability to take pictures.  This does not seem to do anything useful when used on animals or enemies.  Is there a purpose? I came across this proof while looking for hints on my homework, and I think it's only gotten me more confused. This is from .  Lemma 5.4 If $(H,h)$ is a homogeneous Riemannian manifold, then $(H,h)$ is complete. Proof. By the Hopf-Rinow Theorem, it suffices to show that $(H,h)$ is geodesically complete. Thus suppose that $c:[a,1) \rightarrow H$ is a unit speed geodesic which is not extendible to $t=1$. Choosing any $p \in H$, we may find a constant $\alpha &gt; 0$ such that any unit speed geodesic starting at $p$ has length $\ell \geq \alpha$. Set $\delta = \min\{\alpha/2, (1-a)/2\} &gt; 0$. Since isometries preserve geodesics, it follows from the homogeneity of $(H,h)$ that any unit speed geodesic starting at $c(1-\delta)$ may be extended to a geodesic of length $\ell \geq 2 \delta$. In particular, $c$ may be extended to a geodesic $c:[a, 1+\delta) \rightarrow H$, in contradiction to the inextendibility of $c$ to $t=1$.  How exactly does it &quot;follow from homogeneity&quot; that we are able to extend unit speed geodesics? Isn't that what we're trying to show in the lemma? And how does considering geodesics based at $c(1-\delta)$ lead us to extending $c$ to $c:[a,1+\delta) \rightarrow H$? A very quick question:   Is it correct to say "In case I won't be able to watch that"?  If it's acceptable to say that, what type of sentence is it?  UPDATE:  As a clarification, I want to say "Can you give me that in case I won't be able to have it later". Probably, it's more a supposition than a conditional. When I measure a 9V DC wall adapter power supply with a multimeter it shows 11.8V. When connected to my board this voltage lowers to 10V. Is this normal? Should I be afraid of toasting my  supplied board when using this adapter?  Edit: This regulator accepts up to 12V inputs. So that will be no problem. A second "9V" adapter yields 15V to the multimeter. Will this one burn my circuit? I have my bachelors degree in engineering science: computer science, option electrotechnic. I have a good understanding of basic mechanics and dynamics, calculus (differential equations).  The books I'm now having a look at are:       What book do you recommend for studying fluid dynamics on my own and why? Is it allowed/desirable to post code snippets? Instead of asking a question I would love to share the one or other code snippet I have created that is too small to make a full article on e.g. CodeProject.com or CodePlex.com.  Question: Would it be a good idea to post it as a Stack Overflow question? Or are there any other suggestions how to share it?  (Of course I could post it on my own weblog and then twitter about it, but I would love to put it in more of a programming context) The Many Memes of Meta Catchphrases and concepts that spread from person to person are known as [memes], which, courtesy the Internet, can now explode across the Earth like a highly contagious virus (hence &quot;going viral&quot;). As with their real-life counterparts, some infectious diseases are global (pandemic), while others are endemic to specific regions. Stack Overflow, and now even more predominantly Meta Stack Exchange, have seen more than their fair share of these pathological social constructs spread through the user base. They are now ingrained units of our collective culture as SOpedians (a term which I hate, by the way). Just as travelers' immune systems can be assaulted by new diseases in new places, new users are increasingly likely to be miffed by an ingrained meme and left sitting scratching their heads. I therefore propose that this space be used to document the memes endemic to Stack Exchange's culture. Each meme should be listed in a separate answer and I hope that we as a community will be able to provide greater context to each one. Please actually explain each meme in a way understandable to those not already in the know. Especially considering that a lot of these memes aren't really understandable to newer users who weren't around in the early years of the network, or are based on system features that no longer exist.  On other Stack Exchange sites          [memes]: When can a sum and integral be interchanged? Let's say I have $\int_{0}^{\infty}\sum_{n = 0}^{\infty} f_{n}(x)\, dx$ with $f_{n}(x)$ being continuous functions. When can we interchange the integral and summation? Is $f_{n}(x) \geq 0$ for all $x$ and for all $n$ sufficient? How about when $\sum f_{n}(x)$ converges absolutely? If so why? Firmware vs. Software Example of $\deg(fg)<\deg(f)+\deg(g)$ Where to get school zone shapefiles? Census.gov usually makes available the shapefiles containing school zone boundaries. Due to the US government shutdown, census.gov is down. Does anyone know where to download a recently archived copy? Redirect stdout over ssh I would like to run  something &gt; file   on a remote system through ssh, but if I run  ssh host something &gt; file   the redirection is executed locally as ssh etc &gt; file  I've tried it with ' or '' or dd or with a pipe | instead, but I can't get it to work. How can this be done? Normality of dependent variable = normality of residuals? Why does Yoda speak the way he does? Yoda's unique speech consisting of reversed grammar is iconic.  Is there any reason he has adopted this speech pattern?  All other alien species encountered seem to have no trouble speaking normally. Why does Yoda speak in this way? Why can't humans throw objects at bullet speed when the force involved seems so small? The force that propels a bullet should at least be similar in intensity to the force experienced as recoil and the force exerted on the target. But these forces seem really low (the equivalent of a shove).  If all it takes to make a small object achieve bullet speed is the equivalent of a shove, why can't humans throw objects at these speeds? What is the name of the tactic that politicians use to bury people with torrent of words? Some people write bloated books and long essays with skilful use of hooks, e.g. Jared Diamond; some others speak in long-drawn sentences with torrents of words, e.g. Noam Chomsky. It reminds me of a tactic politicians use in public discourse to waste people's time. I came across this word before but I can't retrieve it from either memory or the internet. "Dark L" is "L" at the end of the word or after a vowel sound. Example: ball, pull.  "Light L" is "L" at the beginning or before a vowel sound. Example: light, love.  There are 4 explanations of how to pronounce "dark L":   1st explanation: the tongue tip must contact the ridge right behind the upper teeth. 2nd explanation: before the tongue tip must contact the ridge right behind the upper teeth, you must curl the tongue and make sound like /r/ before make the /l/ as in the 1st explanation. 3rd explanation: just put the tongue between upper and lower teeth is enough to make the dark L 4th explanation: the tongue tip must contact the ridge right behind the upper teeth &amp; the back of the tongue raises up (a British teacher teaches that).   see this vid:  and  for more info  So what is the correct way to make the "dark L"? There are two vectors called $\vec{a}$ and $\vec{b}$. Vector $\vec{c}$ is the bisector and it can be given as  $$\vec{c} = |b|\vec{a} + |a|\vec{b}$$  How to prove that? I have used the dot product method. But there I can't find the angle between them. Then I tried to do this by using unit vectors. Then I got an answer like in the given picture. . Can you help me to get the correct answer What dried food can I take across the American border from Canada?