I am doing something where I want a user to be able to enter a number between 0-9 and it spits out the word for it, eg.  1 into one. I am fine with the first part, however, I don't know how to get it so that it tells the user if it has entered an invalid number or letter.  using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;  namespace _0_9_output {     class Program     {         static void Main(string[] args)         {             Console.Write("Write a number between 0-9: ");             int number = int.Parse(Console.ReadLine());             if (number == 0)             {                 Console.WriteLine("Zero");             }             else if (number == 1)             {                 Console.WriteLine("One");             }             else if (number == 2)             {                 Console.WriteLine("Two");             }             else if (number == 3)             {                 Console.WriteLine("Three");             }             else if (number == 4)             {                 Console.WriteLine("Four");             }             else if (number == 5)             {                 Console.WriteLine("Five");             }             else if (number == 6)             {                 Console.WriteLine("Six");             }             else if (number == 7)             {                 Console.WriteLine("Seven");             }             else if (number == 8)             {                 Console.WriteLine("Eight");             }             else if (number == 9)             {                 Console.WriteLine("Nine");             }             else             {                 (number &gt;= 10);             }              {                 Console.Write("That was an invalid statement.");             }           }     } }   This is one of my first pieces of code so please be generous in giving tips/advice. I am a young programmer and I am only just beginning to learn this in school.
What is the difference between Parse() and TryParse()?  int number = int.Parse(textBoxNumber.Text);  // The Try-Parse Method int.TryParse(textBoxNumber.Text, out number);   Is there some form of error-checking like a Try-Catch Block?
Find all continuous functions $f$ satisfying   $$\int_0^xf=(f(x))^2+C$$ for some constant $C \neq 0$, assuming that $f$ has at most one $0$.  I have a question about the solution to this problem. It says that   Clearly $f^2$ is differentiable everywhere, its derivative at $x$ is $f(x)$ (I'm assuming that this is because the left hand side is differentiable, the right hand side must be differentiable as well). So $f$ is differentiable at $x$ whenever $f(x) \neq 0$, and  $$f(x)=2f(x)f'(x),$$ so $f'(x) = \frac{1}{2}$ at such points. Thus, $f= \frac{1}{2}x+b$ for some $b$ on any interval where it is non-zero; if $f$ has a zero, this gives two possible solutions, with two possible values of $b$, but since $f$ is assumed continuous, they must be the same. So we need $$\int_0^x(\frac{1}{2}t+b)dt=(\frac{1}{2}x+b)^2+C$$  so we must have $b=\sqrt{-C}$ or $-\sqrt{-C}$, leading to two solutions for $C \lt 0$.  I don't understand the bolded statements. First, how does the differentiability of $f^2$ guarantee that $f$ is differentiable, and why only at $x$ where $f(x) \neq 0$?  Next, why are there two possible solutions if $f$ has a zero, but since $f$ is continuous they must be the same?  Finally, does the last statement mean that if $C \gt 0$, then there is no solution, since we're restricted to real numbers here?  I would appreciate it if anyone answers my questions. What is "root" and how can I become it? When I ran a command, I got the following error:     You need to be root to perform this command.   What is root and how can I become it? What's the difference between terms 'link function' and 'canonical link function'? Also, are there any (theoretical) advantages of using one over the other?  For example, a binary response variable can be modeled using many link functions such as logit, probit, etc. But, logit here is considered the "canonical" link function. Does a finite $[E:K]_s$ imply that $[E_s:K]$ is finite? Let $E/K$ be an algebraic extension of fields and denote by $E_s$ the separable closure of $K$ in $E$, i.e. the set of all elements of $E$ that are separable over $K$ (which can be shown is a (separable) subfield of $E$).  I would like to show that the implication     $\left[E:K\right]_s &lt; \infty \implies \left[E_s:K\right] &lt; \infty$   holds, where $\left[E:K\right]_s$ denotes the separable degree of $E/K$ and $\left[E_s:K\right]$ the 'ordinary' degree of $E_s/K$.  In the textbook I am learning with, it is said that one could use the Primitive Element Theorem to do this, but I would also be fine with any other approach, as long as it's not getting too fancy and staying in the realm of 'common' textbook theorems known when dealing with separable extensions (and I didn't see how the Primitive Element Theorem would help).  This is not my focus (I want to write a Bachelor's thesis about polynomial factorizing elements of $\mathbb{Z}[X]$), but I'm in the process of reading into commutative algebra after about 1.5 years break from it.  My idea was something like assuming $\left[E_s:K\right] &lt; \infty$ and $\left[E_s:K\right] = \infty$ to construct infinitely many $K$-homomorphisms $E_s/K \longrightarrow C/K$, where $C$ is some algebraic closure of $E_s$, which would then contradict $\left[E_s:K\right]_s = \left[E_s:K\right] &lt; \infty$. Of course, an infinite basis would yield infinitely many $K$-vector space homomorphisms, but getting (infinitely many) ring morphisms seems to by an entirely different ting (unsurprisingly so...). Thought of using something like     Given two roots of the minimal polynomial of one of the infinitely many elements of a $K$-basis of $E_s/K$, there is a $K$-morphism $E_s/K \longrightarrow C/K$ that sends one to the other.   but this didn't seem very fruitful. I admit I haven't spent hours on this, I just didn't get very far and should focus on moving on, while still getting an answer on the 'howto' along the road would be really nice. Finding an expression for $\tan (a+ b + y)$ which involves only $\tan a, \tan b,$ and $\tan y$. How to find this ?   I'm stuck at $1$ and how to $1$ to change the tangent associated with a,b or c.  I meant this ,everybody.  $\frac{tan(a)+tan(b)+tan(y)−tan(a)tan(b)tan(y)}{1−tan(a)tan(b)−tan(a)tan(y)−tan(b)tan(y)}$ Includepdf causes an error message from pgfplots externalization I have a file test.pdf which I include in a document containing also an externalized pgfplots picture.  When I compile the following code, I get the error message Sorry, the system call pdflatex ... did NOT result in a usable file.  In order to make my code work, I first need to remove the includepdf statement, compile (to create the externalized figures) and then compile again with the includepdf statement.  I suppose that it is a bug, or is there any possibility to solve it ?  Of course, the file test.pdf is totally independent from the externalized pictures from pgfplots.  \documentclass{scrbook}   \usepackage{pgfplots}  \pgfplotsset{compat=1.8}  \usepgfplotslibrary[external]  \tikzexternalize[shell escape=-enable-write18]  \usepackage{pdfpages}   \begin{document} \includepdf{report_test-figure44}   \begin{tikzpicture}  \begin{axis}[  xlabel=Cost, ylabel=Error]  \addplot[color=red,mark=x] coordinates {  (2,-2.8559703) (3,-3.5301677) }; \end{axis}  \end{tikzpicture}   \end{document} How do I change the location of macOS screen captures? As a developer, I take a lot of screen captures. I often take screen shots to share with Stack Exchange members in chat.  The problem is my Desktop is so cluttered with screen captures that they're now overlapping! I'd like to save all screenshots in a dedicated folder or directory.  In macOS, how do I change the default location where screen captures are saved?  These are the screen shots taken with CommandShift3 or CommandShift4 keyboard shortcuts.  I would prefer a solution which doesn't require installing any software. How bias arises in using maximum likelihood to determine the variance of a Gaussian? While reading , I ran into the following explanation for why there is an error in estimating the variance of Gaussian distribution using Maximum Likelihood. On ,      Illustration of how bias arises in using maximum likelihood to   determine the variance of a Gaussian. The green curve shows the true   Gaussian distribution from which data is generated, and the three red   curves show the Gaussian distributions obtained by fitting to three   data sets, each consisting of two data points shown in blue, using the   maximum likelihood results (1.55) and (1.56). Averaged across the   three data sets, the mean is correct, but the variance is   systematically under-estimated because it is measured relative to the   sample mean and not relative to the true mean.   I'm pasting figure 1.15 and the required equations (1.55, 1.56) here for convenience.  $\mu_{ML} = \frac{1}{N}\sum_{n=1}^{N}x_n$   $\sigma_{ML}^2 = \frac{1}{N}\sum_{n=1}^{N}(x_n - \mu_{ML})^2$    I can imagine how maximum likelihood estimation would look pictorially. However, I'm not able to understand the figure or the explanation. I would appreciate if someone could label the figure or explain what points are considered in each part of the figure and why the curve could look like that in each case.  I looked up , and I'm able to understand why there is a factor of $\frac{N-1}{N}$ between the true $\sigma^2$ and $\sigma_{MLE}^2$.  ${\rm I\!E}[\sigma_{MLE}^2]= (\frac{N-1}{N})\sigma^2 $ Why is spectrum obtained by sunlight, said to be continuous? My teacher spoke about atomic spectra today, and he explained that, unlike the spectrum obtained by analyzing the sunlight, the spectra of atoms are not continuous.     I have a question about this - even the sunlight has the radiations emitted by the atoms of the elements which compose the sun, still spectra is continuous, which is in opposition to the statement that atomic spectra is discontinuous. So, spectrum obtained by sunlight is continuous even though it atomic spectra. In order to account for spectrum obtained by the sunlight to be continuous and atomic spectra to be discontinuous, can we confirm that sun consists of all those elements (sodium, helium, neon, mercury, etc) which emit the colors of frequency belonging to visible region? Tighten rope without turnbuckles? I have two 4-ft x 4" x 4" wood posts, and each post has a screw eye. There's 12 feet of distance between each post.  How can I tighten a piece of 1/2" diameter rope that goes through each screw eye and it's stretched tightly without having to buy turnbuckles?  There has to be a knot just for this. Is there any cryptographic algorithm immune to side channel attacks based on scan chain? In VLSI point of view. Integrate $\int \frac{dx}{\sqrt{-ax^2 + bx +c}} $ How should "do my homework" questions be closed? (Missing "demonstrate minimal understanding") Just recently,  question was posted. Here's the body of the question:     Write a function called highlight() that prompts the user for a string. Your code should ensure that the string is all lower case. Next, prompt the user for a smaller 'substring' of one or more characters. Then replace every occurrence of the substring in the first string with an upper case. Finally, report to the user how many changes were made (i.e., how many occurrences of the substring there were).      What would a script for this be?   This is basically a "do my homework for me" style question. In the past, I would have voted to close this question for lacking minimal understanding and moved on. However, it looks like this close reason was removed, and I'm having difficulty figuring out which alternative to use (if at all).  Here were some of the close reasons I was considering, and ultimately decided against since they didn't seem to precisely match:   Duplicate of    I sort of doubt there exists a precise duplicate of this question -- the question is a fairly specific request for some code. I could maybe link to a duplicate question that answers a part of the original (for example, checking if the string is lowercase), but it wouldn't answer every aspect of the problem. Problem that can't be reproduced/typographical error    This sort of matches, since it asks the user to produce a SSCCEE, but doesn't really match since there isn't even a problem to begin with (and closing a question because I couldn't "reproduce" a non-existent problem feels a bit silly to me) Unclear what you're asking    It's pretty obvious what the user is asking -- I could produce a 5 line script in about 20 seconds that precisely matches his spec. Too broad    The text for "Too broad" states that "There are either too many possible answers, or good answers would be too long for this format". This doesn't apply to this question -- once again, the answer I could give would be fairly short and would closely resemble solutions other people would give.   So, what should I do here? Am I misunderstanding how the close reasons should now be used? Should I use the "other" close reason and explain that the OP should have put in more effort? Should I simply downvote, perhaps leave a comment, and move on? Or is the new policy to embrace these kinds of questions and just post an answer? What is going on with pgfpages and page labels? I’m using a feature of beamer that shows notes beside slides, but the page numbers that are coming out are crazy, making it impossible to extract specific slides into other documents with \includegraphics[page=n]{presentation.pdf}.  For example, in this MWE, there are two frames that are each 1 slide, and then one frame that is four slides. The PDF page labels that show up in Acrobat are, as indicated, 2, 3, 3, 3, 3, and 7. It starts at page 2 instead of 1, and then there are four page 3s, but they don’t even all belong to the same frame!  \documentclass{beamer} \usepackage{pgfpages}  \setbeameroption{show notes on second screen=left} \setbeamertemplate{note page}{frame \insertframenumber \\ \insertnote} \def\pg#1{pgfpages says this is page #1 but it is really page \arabic{page}}  \begin{document}  \setcounter{page}{0}  \frame{hi \note{\pg{2}}}  \frame{there \note{\pg{3}}}  \frame{how \pause are \pause you \pause today \note&lt;1-3&gt;{\pg{3}} \note&lt;4&gt;{\pg{7}}}  \end{document}   Here’s what the output looks like:    I know that the manual says, “pgfpages will produce wrong page numbers in the .aux file” and gives a manual workaround. But the page counter still works, so shouldn’t there be some way to pass that through to the PDF? I’d like to fix this, but don’t know where to start. Specifically, when the manual says that “TeX instantiates the page numbers when writing an .aux file only when the physical page is shipped out,” what exactly is it talking about? Where is the source code for that? Does D&D 5e have a rule for character knowledge about monsters? In the 3rd and 4th editions of D&amp;D, there were explicit rules for determining if a character knew anything about a monster before them.  In 3rd edition, for example, use of the  skill with a general DC of 10 + the monster's HD allowed for determining one fact, plus one fact per 5 points over the check.  Looking at the Intelligence section of the 5e PHB, I don't see any similar notation.  Does 5e provide any guidance as to when a player could use their out-of-game knowledge about a monster, or when the player might be told things their character would probably know in-game? I have this graphic. I need to change the color of the graphic to hex color: 1485cc...is there a way to make this graphic match that particular hex color hue...without me having to have to re create the graphic. How do i prove that continuous linear transformation between normed spaces is bounded? Let $(V,||\cdot||_V),(W,||\cdot||_W)$ be normed spaces over $\mathbb{C}$.  Let $T:V\rightarrow W$ be a linear transformation.  Assume $T$ is continuous.  Then, how do i prove that $\exists c&gt;0$ such that $\forall v\in V, ||Tv||_W&lt;c||v||_V$? Identifying Unused Stored Procedures This next year, I am helping an effort to clean several SQL Server environments.    We have about 10,000 stored procedures and estimate that only about 1000 of them are used on a regular basis, and another 200 or so are used on a rare occasion, meaning we have a lot of work to do.    Since we have multiple departments and teams that can access these databases and procedures, we are not always the ones calling the procedures, meaning that we must determine what procedures are being called.  On top of that, we want to determine this over a few months, not in a few days (which eliminates some possibilities).  One approach to this is to use the SQL Server Profiler and track what procedures are being called and compare them to the list of what procedures we have, while marking whether the procedures are used or not.  From then, we could move the procedures to a different schema in case a department comes screaming.  Is using the Profiler the most effective approach here?  And/Or have any of you done something similar and found another way/better way to do this? Can't boot into Ubuntu in Windows 10 / Ubuntu dual boot I installed Ubuntu on a Dell XPS 13 laptop that had Windows 10 preinstalled on it. I installed it from a USB flash drive on a partition. When I boot my computer I can only boot into Windows 10 and Ubuntu is nowhere to be seen.  If I boot into my USB then I can see that Ubuntu is installed, but I can't get to it from the BIOS boot menu. OS X lets me type special characters directly on the keyboard by holding the Option. For example: — is an em dash, “ and ” are curvy quotes, etc.  Is there a good cheat sheet listing all these keys somewhere? I tend to find myself holding option and running my hands up and down the keyboard looking for a specific character.