"is a field but is being treated like a type" error
"is a field and used like a type" error
Let n be an even integer. How many different ways can I choose subsets of the set {1,2...,n} Let n be an even integer. How many different ways can I choose subsets of the set {1,2...,n} if they all have to have odd size, but the intersection of any two of them has to have even size?  Please help me answer this question or lead me in the right direction. Thank you :) I'm reading Nano: The Essentials by T. Pradeep and I came upon this statement in the section explaining the basics of scanning electron microscopy.     However, the equation breaks down when the electron velocity approaches the speed of light as mass increases. At such velocities, one needs to do relativistic correction to the mass so that it becomes[...]   We all know about the famous theory of relativity, but I couldn't quite grasp the "why" of its concepts yet. This might shed new light on what I already know about time slowing down for me if I move faster.  Why does the (relativistic) mass of an object increase when its speed approaches that of light? I've been having trouble defeating this monster. Even with lots of buff potions, health potions, high tier armor (Molten), and ranged weapons with plenty of ammo (Minishark), I can't seem to kill this boss.  Worse, when I get it down to about 2000 hp, even if I'm fairly far away, it'll suck me in and continually rise towards the skybox, which doesn't allow me to do anything for some reason.  How do I defeat the Wall of Flesh? What gear should I be using and what kind of potions do I need? I have been asked by a client to implement some views for reporting purposes, the views will be accessed via PowerBI, Excel and SSRS. The designated user will only have access to the view and no underlying tables must be available to the user.  The problem I have encountered in that the SQL within the view touches 3 different schemas (All within the same database):   Pupil Provider  Security   The view is:  CREATE VIEW dbo.vTestPermissions AS SELECT a.Column1,        b.Column1,        c.Column1 FROM Pupil.Table1 a JOIN Provider.Table2 b ON a.Column1 = b.Column1 JOIN Security.Table3 c ON a.Column1 = c.Column1   The owners of the Tables/View are as follows:   Pupil.Table1 - Owner Pupil Provider.Table2 - Owner Provider Security.Table3 - Owner Security vTestPermissions - Owner dbo   When I select from the view I get an error:     The SELECT permission was denied on the object 'table3', database   'TEST', schema 'Security'   I have tried giving SELECT permission with and without the GRANT option to the schema, and the tables, but that makes the underlying tables available to the user.  Any help on this will be greatly appreciated. $\forall$ At the beginning or at the end? I have a set of real numbers $x_1, x_2, \ldots, x_n$ and two functions $f:\mathbb{R} \rightarrow \mathbb{R}$ and $g:\mathbb{R} \rightarrow \mathbb{R}$.  What are the differences between the following statements?   $\forall v \in \{1, \ldots, n\} ~f(x_v) = 0 \vee g(x_v) = 0$ $f(x_v) = 0 \vee g(x_v) = 0 ~\forall v \in \{1, \ldots, n\} ~$ Does leaning (banking) help cause turning on a bicycle? How to make traditional output for derivatives Suppose that we don't know logarithm, then how we would able to calculate $\sqrt x$, where $x$ is a real number? More generally, is there any algorithm to calculate $\sqrt [ n ]{ x } $ without using logarithm? More simple techniques would be nice.  Here is a simple technique used to approximate square roots by :  For example: $\sqrt {78}\approx 8\frac { 14 }{ 17 } $ , where $8$ is the nearest integer root of $78$, $14 = 78 - 8^2$, $17 = 2 \times 8 + 1$.  if $n=2^k$ we can use the method above.   For example, for $k=2$ Lets calculate $\sqrt [ 4 ]{ 136 } $: $$\sqrt [ 4 ]{ 136 } =\sqrt { \sqrt { 136 }  } \approx \sqrt { 11\frac { 136-{ 11 }^{ 2 } }{ 11\times 2+1 }  } =\sqrt { 11\frac { 15 }{ 23 }  } \\ \sqrt { 11\frac { 15 }{ 23 }  } \approx 3\frac { 11\frac { 15 }{ 23 } -{ 3 }^{ 2 } }{ 3\times 2+1 } =\frac { 544 }{ 161 } =3.38\\$$ The exact result is$$ \sqrt [ 4 ]{ 136 } =3.4149\cdots$$ The method approximates well, but it is working for only $n=2^k$ as I know. Minimum value of $\left(a+\frac{1}{b}\right)^2+\left(b+\frac{1}{c}\right)^2+\left(c+\frac{1}{a}\right)^2$ Given $a,b,c \in \mathbb{R^+}$ such that $a+b+c=12$   Find Minimum value of $$S=\left(a+\frac{1}{b}\right)^2+\left(b+\frac{1}{c}\right)^2+\left(c+\frac{1}{a}\right)^2$$  My Try: By Cauchy Schwarz Inequality we have  $$\left(a+\frac{1}{b}\right)+\left(b+\frac{1}{c}\right)+\left(c+\frac{1}{a}\right)\le \sqrt{3}\sqrt{S}$$  $\implies$  $$\sqrt{3S} \ge 12+\frac{1}{a}+\frac{1}{b}+\frac{1}{c}$$  Now by $AM \ge HM $ inequality we have  $$\frac{a+b+c}{3} \ge \frac{3}{\frac{1}{a}+\frac{1}{b}+\frac{1}{c}}$$ $\implies$  $$\frac{1}{a}+\frac{1}{b}+\frac{1}{c} \ge \frac{3}{4}$$  hence  $$\sqrt{3S} \ge 12+\frac{3}{4}=\frac{51}{4}$$  hence  $$3S \ge \frac{2601}{16}$$  so $$S \ge \frac{867}{16}$$  is this approach correct and any better approach please share. Benefit of date in URL segments I was curious about the date in URL segments, is there any SEO point of benefit? For example the following URLs:  http://techcrunch.com/2013/06/18/netflix-will-launch-in-the-netherlands-later-this-year-as-its-international-expansion-slows/ http://tips-for-new-bloggers.blogspot.in/2007/02/adding-favicon-icon-to-blogger-url.html  https://community.jivesoftware.com/blogs/jivespace/2013/05/15/eol-of-the-html5-ipad-web-app   In all the above URLs there is date segment. The information of those blogs can be fetched via blog stub like "netflix-will-launch-in-the-netherlands-later-this-year-as-its-international-expansion-slows" so why to use that date part? In my Java application, I want to run a batch file that calls "scons -Q implicit-deps-changed build\file_load_type export\file_load_type"  It seems that I can't even get my batch file to execute. I'm out of ideas.   This is what I have in Java:  Runtime.    getRuntime().    exec("build.bat", null, new File("."));   Previously, I had a Python Sconscript file that I wanted to run but since that didn't work I decided I would call the script via a batch file but that method has not been successful as of yet. What does a dot after the file permission bits mean? I performed an ls -la on directory on my CentOS 6.4 server here and the permissions for a given file came out as:  -rwxr-xr-x.   I understand what -rwxr-xr-x means, what I don't understand is the . after the last attribute.  Can someone explain it to me? Is it harmful in any way? Can it be removed? note: this question has been updated to reflect that we are currently using MySQL, having done so, I would like to see a how much easier it would be if we switched to a CTE-supporting database.  I have a self-referencing table with a primary key, id and a foreign key parent_id.  +------------+--------------+------+-----+---------+----------------+ | Field      | Type         | Null | Key | Default | Extra          | +------------+--------------+------+-----+---------+----------------+ | id         | int(11)      | NO   | PRI | NULL    | auto_increment |  | parent_id  | int(11)      | YES  |     | NULL    |                |  | name       | varchar(255) | YES  |     | NULL    |                |  | notes      | text         | YES  |     | NULL    |                |  +------------+--------------+------+-----+---------+----------------+   Given a name, how can I query the top-level parent?  Given a name, how can I query all of the id's associated with a record of name = 'foo'?  context: I am not a dba, but am planning to ask a dba to implement this type of hierarchical structure and would like to test some queries. The motivation for doing so is described by .    Here is an example of the relationships among ids in the table:    -- ----------------------------------------------------- -- Create a new database called 'testdb' -- ----------------------------------------------------- SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0; SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0; SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='TRADITIONAL';  CREATE SCHEMA IF NOT EXISTS `testdb` DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci ; USE `testdb` ;  -- ----------------------------------------------------- -- Table `testdb`.`observations` -- ----------------------------------------------------- CREATE  TABLE IF NOT EXISTS `testdb`.`observations` (   `id` INT NOT NULL ,   `parent_id` INT NULL ,   `name` VARCHAR(45) NULL ,   PRIMARY KEY (`id`) ) ENGINE = InnoDB;  SET SQL_MODE=@OLD_SQL_MODE; SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS; SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS;  -- ----------------------------------------------------- -- Add Example Data Set -- -----------------------------------------------------   INSERT INTO observations VALUES (1,3), (2,5), (3,NULL), (4,10),     (5,NULL), (6,1), (7,5), (8,10), (9,10), (10,3); I have two PHP scripts, both using the same session by calling session_name('MySessID').  When the first script calls the second script using curl, the second script hangs when session_start() is called.  Why would this happend? Modus Operandi. Formulae for Maximum and Minimum of two numbers with a + b and $|a - b|$ I came across the following problem in my self-study of real analysis:     For any real numbers $a$ and $b$, show that $$\max \{a,b \} = \frac{1}{2}(a+b+|a-b|)$$ and $$\min\{a,b \} = \frac{1}{2}(a+b-|a-b|)$$   So $a \geq b$ iff $a-b \ge0$ and $b \ge a$ iff $b-a \ge 0$. At first glance, it seems like an average of distances. For the first case, go to the point $a+b$, add $|a-b|$ and divide by $2$. Similarly with the second case.   Would you just break it up in cases and verify the formulas? Or do you actually need to come up with the formulas? How can I narrow down these gaps? I am writing my curriculum vitae, but I have one question.  In the first image, there are spaces between different sections.  (Between contact and phone, between education and Seoul~~,....)  Thus, I want to narrow down these gaps.  How can I solve this problem??  \documentclass[margin,line,letterpaper,11pt]{res}  \usepackage{times}  \usepackage{enumitem}   \setlength{\topmargin}{0.1in} \setlength{\textheight}{11in}  \setlength{\textwidth}{6in} \setlength{\oddsidemargin}{-.55in}  \setlength{\evensidemargin}{-.55in}  \oddsidemargin -.25in \evensidemargin -.49in \textwidth=5.4in  \newcommand{\ts}{\textsuperscript}  \newcommand{\block}[1]{     \vspace{.1in} \section{\sc #1} }  \newcommand{\subblock}[1]{     \vspace{-.2in}\subsection*{#1} }  \newenvironment{enum}{     \begin{enumerate}[leftmargin=5mm]     \setlength{\itemsep}{1mm} }{     \end{enumerate} }   \begin{document}   \name{\sc \LARGE  }   \begin{resume}  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  \block{Contact} Phone:  \\ Email:  \\\vspace*{-6mm} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  \block{Education}  University : \\  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  \block{Other\\ Activities}  Club : \\   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  \end{resume} \end{document} Test for existence of nested JavaScript object key I am wondering if the explanations correct and whether what is the difference between different &quot;seems&quot;.   He seems happy. He seems a happy fellow. He seems to be a happy fellow. He seems to work hard. He seemed to be happy   &quot;Seem&quot; also enters into an 'impersonal' construction which employs 1) the 'dummy' subject it + an active tensed form with &quot;seem&quot;, followed by 2) a that clause (sometimes called a 'content' clause) which expresses the assertion which is hedged or qualified.   It seems that he is happy (but he may not be).  It seemed that he was a happy fellow (but he wasn't).  It will seem that he is working hard (but he will in fact be spending his time answering questions on ELL instead of working).  He is seemed to be something. I'd like to emulate HTML's infinite page height using LaTeX/XeTeX, i.e. have the PDF pages grow higher until a manual \newpage is issued.  This could be emulated by setting a very large page height and using pdfcrop on the output (or just setting the page height manually), but I'd like a pure TeX variant and if possible support for footnotes etc at the bottom of the cropped page. How can I reproduce the error "package... needs to be reinstalled, but I can't find an archive for it" for testing? From time to time, Ubuntu users encounter errors from  or , of the form:  The package some-package needs to be reinstalled, but I can't find an archive for it.  I want to know what causes this error so that I can reproduce it and try to find safe ways of fixing it, even when the broken package is important and has many dependencies.  of the  might give a bit of a clue, but I don't know how packages get the status that causes the error.  How can I produce this error for testing on my (Ubuntu MATE 17.10) system?  This is prompted by  and my long-standing discomfort with closing questions about this error against , whose answer uses dpkg --force-all to remove the offending package.  suggests this solution has worked for many users, but I am not confident that using --force-all won't cause later problems, or that it's a good idea to use this method to remove important packages like APT.