How to parse a date?
Java string to date conversion
What is a good algorithm for estimating the median of a huge read-once data set? From the TV Show Krypton, Dru-Zod is the son of Seg-El and Lyta-Zod. In S02E05 'A better yesterday', Lyta-Zod's throat gets slit by Jax-Ur leading to Lyta's death. How is Dru-Zod still alive? Shouldn't he be wiped from existence? Why is the gradient of implicit surface the normal vector (i.e. parallel to the normal line)? If we have an implicit surface $g(x, y, z)=...$, the gradient is a normal vector. But why? Do I have to start with tangent vectors and then show the gradient is perpendicular? Not sure how to approach this. Is it feasible to compile Python to machine code? mysql_fetch_array()/mysql_fetch_assoc()/mysql_fetch_row()/mysql_num_rows etc... expects parameter 1 to be resource I am going through Shankar's Principles of Quantum Mechanics and am having trouble finding the free particle propagator $U(t)$ that satisfies $$\lvert\psi (t)\rangle = U(t)\lvert\psi (0)\rangle$$ due to the degeneracy of the $E$ eigenkets. Shankar says that if the Hamiltonian has degenerate eigenvalues, we change the propagator equation from $$U(t) = \sum_{E} \lvert E\rangle\langle E\rvert e^{-iEt/{\hbar}}\tag{4.3.13}$$ to $$U(t) = \sum_{E} \sum_\alpha \lvert E, \alpha\rangle\langle E, \alpha\rvert e^{-iEt/\hbar} $$ where $\lvert E, \alpha \rangle $ are the orthonormal eigenkets for the $E$ eigenspace. This makes sense to me, because it seems like whenever we deal with degeneracy to use a projection. He also says for a Hamiltonian with no degeneracy to change the sum into an integral, so I imagine that for a Hamiltonian with a continuous, degenerate spectrum we would have this propagator: $$ U(t) = \sum_\alpha\int_\Re dE\lvert E, \alpha\rangle\langle E, \alpha\rvert e^{-iEt/\hbar}$$  I tried applying this to the free particle and had some trouble. In the book, after solving for the eigenkets and eigenvalues, $\lvert E\rangle = \lvert p\rangle$ and $p = \pm\sqrt{2mE}$, he chooses the propagator as a function of the momentum eigenvalues $p$ so that $$U(t) = \int_\Re dp\lvert p\rangle\langle p\rvert \exp(-ip^2t/2m).\tag{5.1.9}$$ I understand how he got to this, but I'm having some trouble because this doesn't appear to be the same expression that I have above. Splitting the integral up, we have $$U(t) = \int_{-\infty}^0dp\lvert p\rangle\langle p\rvert \exp(-ip^2t/2m) + \int_0^\infty dp\lvert p\rangle\langle p\rvert \exp(-ip^2t/2m)$$ The left integral can changed to an integral over $-p$, and the bounds switch from $0$ to $\infty$ such that: $$U(t) =  \int_{0}^\infty d(-p)\lvert -p\rangle\langle -p\rvert \exp(-ip^2t/2m) + \int_0^\infty dp\lvert p\rangle\langle p\rvert \exp(-ip^2t/2m)$$ Now we can substitute and interchange $\lvert p\rangle = \lvert E, + \rangle$,  $\lvert -p\rangle = \lvert E, - \rangle$, $E = p^2/2m$, and $dp = \pm mdE/\sqrt{2mE}$ to get: $$U(t) = \sum_{\alpha = \pm} \int_0^\infty dEm/\sqrt{2mE}\lvert E, \alpha\rangle\langle E, \alpha\rvert e^{-iEt/\hbar}. $$ This is the result that we are asked to prove in Exercise 5.1.1. Why is this not the same as the first expression for the propagator? Where did the extra $ m/\sqrt{2mE} $ come from? Am I just wrong in assuming that that is the general expression for a Hamiltonian with continuous and degenerate eigenvalues? How to design the attack class in an RPG game? How can I automatically download lyrics in iTunes? Is there a way to automatically download lyrics in iTunes? Prove that $f'(a)=\lim_{x\rightarrow a}f'(x)$. Let $f$ be a real-valued function continuous on $[a,b]$ and differentiable on $(a,b)$. Suppose that $\lim_{x\rightarrow a}f'(x)$ exists. Then, prove that $f$ is differentiable at $a$ and $f'(a)=\lim_{x\rightarrow a}f'(x)$.    It seems like an easy example, but a little bit tricky. I'm not sure which theorems should be used in here.    ==============================================================  Using @David Mitra's advice and @Pete L. Clark's notes I tried to solve this proof. I want to know my proof is correct or not.  By MVT, for $h&gt;0$ and $c_h \in (a,a+h)$ $$\frac{f(a+h)-f(a)}{h}=f'(c_h)$$ and $\lim_{h \rightarrow 0^+}c_h=a$.    Then $$\lim_{h \rightarrow 0^+}\frac{f(a+h)-f(a)}{h}=\lim_{h \rightarrow 0^+}f'(c_h)=\lim_{h \rightarrow 0^+}f'(a)$$   But that's enough? I think I should show something more, but don't know what it is. How can I speed up combat with a large number of enemies? I'm DMing for a campaign where the player characters will sometimes face small squads of creatures, most recently six ground troops and two archers helping out. In this setting, these creatures dominate the land the PCs are in and have an organised military, hence squads of enemies.  Combat tends to go quite slowly, however. Eight enemies and three players means the players spend a lot of time waiting between their turns!  Without reducing the number of enemies in the encounter, how can I speed up combat when the players are fighting many enemies? Reputation misaligned in new topbar LLC-SCorp to self - actually, does the corp pay payroll taxes? In the USA. Here are the two common scenarios for the self-employed:  A. Joe makes 100,000 over the year. It's paid to him as 1099 payments from his various clients.  Joe pays the many taxes on that.  B. Joe makes 100,000 over the year.  He has an LLC as SCorp (or maybe an SCorp per se).  The clients pay $100,000 to the entity JoeCorp.  JoeCorp pays Joe a certain salary (it might be the whole 100,000, or, it might be (let's say) half of that and the rest is taken as profit distribution, not relevant here).  So, JoeCorp (his LLC) pays Joe say $50,000.  In fact: does JoeCorp have to pay "payroll taxes" on that??  Does it perhaps make a difference if it is an LLC with S-Corp election v. S-Corp?  (I realize there are many questions on here about "1099 v. corp" .... but I've never really understood this and can't seem to google it up.) Active vs passive voice with inanimate object as the subject I have asked the  in ELL Stackexchange forum. There all the answers and comments I received was really helpful, but still I was looking for something more. So I have decided to ask this same question here also.   I have seen some sentences like this -         The film was announced to be released on this coming Friday.   The film was announced to release on this coming Friday.      Both the sentences are used, and I know they are interchangeable and does bear the same meaning. But I have some doubt about the second sentence - why is it "to release", when the film cant release itself.   Some other sentences of similar structure that arises my confusion -         The product sells well.   The book reads well.   The glass broke.      The sentences are understandable, but in each of the sentences the subjects can't perform any job, as they all are inanimate object. The verbs are active, but they acts like they are used as passive.  Now my question is how to decide which verb to use this way and which not? How do I merge two dictionaries in a single expression (taking union of dictionaries)? Running two MySQL servers that use the same data directory Chrome and Firefox cannot add specific URL to home screen Typsetting the Ponny Today, once again, the  came to my attention and I have decided to try to  using XeLaTeX. The result is far from perfect, worse even than Chrome's rendering.  Is there a way I can improve the result? Is XeLaTeX and LuaLaTeX incapable of handling the Ponny?  :  \documentclass[]{article} \usepackage{lmodern} \usepackage{amssymb,amsmath} \usepackage{ifxetex,ifluatex} \usepackage{fontspec} \defaultfontfeatures{Mapping=tex-text,Scale=MatchLowercase} \IfFileExists{upquote.sty}{\usepackage{upquote}}{} \IfFileExists{microtype.sty}{\usepackage{microtype}}{} \usepackage[normalem]{ulem} \setmainfont{Doulos SIL}  \title{html - RegEx match open tags except XHTML self-contained tags - Stack Overflow} \date{} \author{StackOverflow}  \begin{document} \maketitle  Rege̿̔̉x-based HTML parsers are the cancer that is killing StackOverflow \emph{it is too late it is too late we cannot be saved} the trangession of a chi͡ld ensures regex will consume all living tissue (except for HTML which it cannot, as previously prophesied) \emph{dear lord help us how can anyone survive this scourge} using regex to parse HTML has doomed humanity to an eternity of dread torture and security holes \emph{using rege}x as a tool to process HTML establishes a brea\emph{ch between this world} and the dread realm of c͒ͪo͛ͫrrupt entities (like SGML entities, but \emph{more corrupt) a mere glimp}se of the world of reg​\textbf{ex parsers for HTML will ins}​tantly transport a p\emph{rogrammer's consciousness i}nto a w\emph{orl}d of ceaseless screaming, he comes\sout{, the pestilent sl}ithy regex-infection wil​\textbf{l devour your HT}​ML parser, application and existence for all time like Visual Basic only worse \emph{he comes he com}es \emph{do not fi}​ght h\textbf{e com̡e̶s, ̕h̵i}​s un̨ho͞ly radiańcé de\emph{stro҉ying all enli̍̈́̂̈́ghtenment, HTML tags \textbf{lea͠ki̧n͘g fr̶ǫm ̡yo​͟ur eye͢s̸ ̛l̕ik͏e liq}​uid p}ain, the song of re̸gular exp​re\sout{ssion parsing} will exti\emph{​nguish the voices of mor​\textbf{tal man from the sp}​here I can see it can you see ̲͚̖͔̙î̩́t̲͎̩̱͔́̋̀ it is beautiful t​}he f\texttt{inal snuf}fing o\emph{f the lie​\textbf{s of Man ALL IS LOŚ͖̩͇̗̪̏̈́T A}}\textbf{LL I​S L}OST th\emph{e pon̷y he come}s he c̶̮om\sout{es he co}\textbf{\sout{me}s t\emph{he} ich​}or permeat\emph{es al}l MY FAC\emph{E MY FACE ᵒh god n\textbf{o NO NOO̼}}\textbf{O​O N}Θ stop t\emph{he an​*̶͑̾̾​̅ͫ͏̙̤g͇̫͛͆̾ͫ̑͆l͖͉̗̩̳̟̍ͫͥͨ}e̠̅s\texttt{ ͎a̧͈͖r̽̾̈́͒͑e} n\textbf{​ot rè̑ͧ̌aͨl̘̝̙̃ͤ͂̾̆ ZA̡͊͠͝LGΌ ISͮ̂҉̯͈͕̹̘̱ T}O͇̹̺ͅƝ̴ȳ̳ TH̘\textbf{Ë͖́̉ ͠P̯͍̭O̚​N̐Y̡ H̸̡̪̯ͨ͊̽̅̾̎Ȩ̬̩̾͛ͪ̈́̀́͘ ̶̧̨̱̹̭̯ͧ̾ͬC̷̙̲̝͖ͭ̏ͥͮ͟Oͮ͏̮̪̝͍M̲̖͊̒ͪͩͬ̚̚͜Ȇ̴̟̟͙̞ͩ͌͝}S̨̥̫͎̭ͯ̿̔̀ͅ  \end{document}   UPDATE  Using the Doulos SIL font gets me something closer to what Firefox renders but still far from perfect. Return matched elements' attribute ar array using jQuery Deleting a comment (mine) shouldn't count as a comment vote Difference between "little" and "small" Is there a difference between them? If so, how and when are they used?  For example:     I fixed a little/small typo.