I am learning C# throught the C# via CLR book. And I come across the following piece of code (simplified to create minimal example):  using System;  public class Program  {     public static void Main(String[] args)     {      string text = "Test";      string reversed = new String(text.Reverse().ToArray());       Console.WriteLine(reversed);    } }   Before trying to run the code above a compiler tells the following:     'string' does not contain a definition for 'Reverse' and no accessible extension method 'Reverse' accepting a first argument of type 'string' could be found (are you missing a using directive or an assembly reference?) [Console.NET]csharp(CS1061)   I can not wrap my head where the Reverse method come from. Was the Reverse method present in an older version of C#?  Original code is the last page of the Delegates topic (417-418 page).
I've just had to write a string reverse function in C# 2.0 (i.e. LINQ not available) and came up with this:  public string Reverse(string text) {     char[] cArray = text.ToCharArray();     string reverse = String.Empty;     for (int i = cArray.Length - 1; i &gt; -1; i--)     {         reverse += cArray[i];     }     return reverse; }   Personally I'm not crazy about the function and am convinced that there's a better way to do it. Is there?
I've tried to render my scene but there's an object that won't show up. I've checked the camera, I've checked the visibility, it isn't hidden and it's showing in the viewport. I feel like I've opened every setting and have achieved nothing. I’m trying to render a book with a cover, flipping pages and stacks of pages. I have no idea how to fix the fact that the book cover doesn’t render. If I create a plane and select both the book cover and the plane and join them with Ctrl+J, the render contains a book cover but it doesn’t turn as it’s rigged to do so because it’s now linked to the plane and loses all the animated properties. As soon as I unjoin them the book cover stops rendering and everything appears as you see it there, a book with binding, pages, but no cover. For the life of me I cannot figure out what’s going on. There's a link to the file here: When I try to install a software using Ubuntu Software center I get:  Failed to download repository information Check Your Internet connection   When I try to do a apt-get install something, I get:  407  Proxy Authentication Required   I use a proxy server that requires a user-name and a password. I have set my systems proxy manually, by plugging in the required numbers in the Networks proxy and applied it system wide. I guess the problem now is plugging in my user-name and password.  When I use INTERNET via Mozilla, it specifically asks me for my user-name and password. Set spawn point for a specific player I made a server and me and one of my friends want to do a prank on another friend, because he stole all my enchanted diamond armor.  The Prank  I want to set a player's spawn point in a pit of lava, how would I do this without affecting anyone else's spawn point? Use Results of Find Command to Call vi Is there a way that I can pipe the output of this command (assuming there is only one file found) to vi.  I want to find this command, and then call it up in vi.  Thanks.  find . -name 'id.properties' This button is in the new Firefox, but what is the name of it? I keep getting the message MobileMe Service Stopped Working each time I open Outlook 2007. I have to click on the Close Program button in the error message twice each time it shows up while Outlook is trying to load up. Then I am able to use Outlook. I never use my iCloud account and would like to know how I can deactivate iCloud so I do not have issues with my Outlook. Coupon collector's problem: mean and variance in number of coupons to be collected to complete a set (unequal probabilities) There are $n$ coupons in a collection. A collector has the ability to purchase a coupon, but can't choose the coupon he purchases. Instead, the coupon is revealed to be coupon $i$ with probability $p_i=\frac 1 n$. Let $N$ be the number of coupons he'll need to collect before he has at least one coupon of each type. Find the expected value and variance of $N$. Bonus: generalize to the case where the probability of collecting the $j$th coupon is $p_j$ with $\sum\limits_{j=1}^n p_j=1$  I recently came across this problem and came up with/ unearthed various methods to solve it. I'm intending this page as a wiki with various solutions. I'll be posting all the solutions I'm aware of (4 so far) over time.    EDIT: As mentioned in the comments, this question is different from the one people are saying it is a duplicate of since (for one thing) it includes an expression for the variance and it covers the general case where all coupons have unequal probabilities. The case of calculating the variance for the general case of coupons having unequal probabilities has not been covered anywhere on the site apart from , which this one intends to consolidate along with other approaches to solve this problem.    EDIT: Paper on the solutions on this page submitted to ArXiv: Prove that for any positive integer $n$, $$2\sqrt{n + 1} − 2 \le 1 +\frac 1 {\sqrt 2}+\frac 1 {\sqrt 3}+ \dots +\frac 1 {\sqrt n} \le 2\sqrt n − 1$$ Progress I think Riemann sum should be used for the middle term. I got the limit as $n\to \infty$ of the function inside using Riemann sum but what I cannot get are the lower and upper bound. Is it possible to write some C or C++ code and compile to binaries, then use those binaries with php? Is it also possible to write a php library using C and C++ ?  If so, please tell how can I do so? Considering this code, can I be absolutely sure that the finally block always executes, no matter what something() is?  try {       something();       return success;   }   catch (Exception e) {        return failure;   }   finally {       System.out.println("I don't know if this will get printed out"); } What is the best way to open a file for exclusive access in Python? What is the most elegant way to solve this:   open a file for reading, but only if it is not already opened for writing open a file for writing, but only if it is not already opened for reading or writing   The built-in functions work like this  &gt;&gt;&gt; path = r"c:\scr.txt" &gt;&gt;&gt; file1 = open(path, "w") &gt;&gt;&gt; print file1 &lt;open file 'c:\scr.txt', mode 'w' at 0x019F88D8&gt; &gt;&gt;&gt; file2 = open(path, "w") &gt;&gt;&gt; print file2 &lt;open file 'c:\scr.txt', mode 'w' at 0x02332188&gt; &gt;&gt;&gt; file1.write("111") &gt;&gt;&gt; file2.write("222") &gt;&gt;&gt; file1.close()   scr.txt now contains '111'.  &gt;&gt;&gt; file2.close()   scr.txt was overwritten and now contains '222' (on Windows, Python 2.4).  The solution should work inside the same process (like in the example above) as well as when another process has opened the file. It is preferred, if a crashing program will not keep the lock open. Find all roots of $\,x^2\!\equiv x\pmod{\!900}$, i.e all idempotents in $\Bbb Z_{900}$ I need the idempotent elements of $Z_{900}$ $2^2\cdot 3^2\cdot 5^2=900$ Of course there's $$0 \pmod 4 \\ 0 \pmod 9 \\ 0 \pmod {25} \\ $$ and $$ 1 \pmod 4 \\ 1 \pmod 9 \\ 1 \pmod {25} \\ $$ I found the answers by making a C++ program to test all numbers, but I don't know how to quick solve on paper. This is the output of the program $(0, 0, 0) \rightarrow 0 \\ (1, 1, 1) \rightarrow 1 \\ (0, 0, 1) \rightarrow 576 \\ (0, 1, 0) \rightarrow 100 \\ (1, 0, 0) \rightarrow 225 \\ (1, 1, 0) \rightarrow 325 \\ (0, 1, 1) \rightarrow 676 \\ (1, 0, 1) \rightarrow 801 \\$ How to concatenate items in a list to a single string? Is password confirmation necessary on a Change Password dialog? On one hand there is no need to ask for password confirmation because it is annoying. If I made a mistake when confirming my password I'll need retype my very complex password again. There is also a button that can show/hide the password so I don't need retype it in order to confirm it.   However, some users don't use the password show/hide button and the 'forgotten password' option will be pain for them.  Twitter removed the password confirmation from registration but left the dual confirmation in place for changing password. Is this right approach? Java; String replace (using regular expressions)? As part of a project for school, I need to replace a string from the form:  5 * x^3 - 6 * x^1 + 1   to something like:  5x&lt;sup&gt;3&lt;/sup&gt; - 6x&lt;sup&gt;1&lt;/sup&gt; + 1   I believe this can be done with regular expressions, but I don't know how to do it yet.  Can you lend me a hand?   P.S. The actual assignment is to implement a Polynomial Processing Java application, and I'm using this to pass polynomial.toString() from the model to the view, and I want do display it using html tags in a pretty way. When is a review task "completed" or "invalidated"? I've noticed that the number of reviews required to remove a post from a queue varies. For example, to accept/reject a suggested edit, you need two votes of the same kind. If the votes are conflicting, the number goes higher. This seems to be the case for the other queues as well. (Additionally, I think that a mod-review is binding) So, my question is: what are the criteria for a review to be marked as a &quot;completed&quot; review? Also, when is a review considered invalidated (i.e. &quot;no longer reviewable&quot;)? Formerly When is a post removed from a review queue?. Word/phrase to mean something that just happens once What is the word/phrase to mean something that just happens once? For example,     I have often been told/expected to do this and not to do that. I become aimless   and gradually lose the idea of who I am. I ask myself "What is the point?" If   life is just once thing, why can't I live my life in my own way,   the way I think is right and suitable to me? If I cannot, I would   rather live a shorter life. Add alias URL for posts timeline Fermat's Last Theorem with negative exponent Combine the output of two commands in bash Is it possible to combine output from these two commands?  node ~/projects/trunk/index.js  python ~/projects/trunk/run.py run   Neither command exits so I'm not sure how to do this.