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• Data entry screen in asp.net MVC

  - by Vikas

  You may thick that it is a silly question but I am confused! I have a situation that I have a Lecture table. And I want to store attendance of who have registered for it. I have master table of People who will register, lecture table, and Important one table is attendance that stores P.k. as f.k. of rest of the table. On Index view of lecture operator will select Attendance and enter attendance information. My problem It show only one page for attendance entry and that page can also open open in EDIT mode, for editing attendance. So what would be the design of the page and process flow of taking attendance?

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• NASM shift operators

  - by Hudson Worden

  How would you go about doing a bit shift in NASM on a register? I read the manual and it only seems to mention these operators , <<. When I try to use them NASM complains about the shift operator working on scalar values. Can you explain what a scalar value is and give an example of how to use and <<. Also, I thought there were a shr or shl operators. If they do exist can you give an example of how to use them? Thank you for your time.

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• Does std::multiset guarntee insertion order?

  - by Naveen

  I have a std::multiset which stores elements of class A. I have provided my own implementation of operator< for this class. My question is if I insert two equivalent objects into this multiset is their order guaranteed? For example, first I insert a object a1 into the set and then I insert an equivalent object a2 into this set. Can I expect the a1 to come before a2 when I iterate through the set? If no, is there any way to achieve this using multiset?

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• C# : Number Conversion Problem

  - by Sayem Ahmed

  Today I faced a strange problem in C#. I have an ASP.NET page where user can enter certain price, quantity etc. I get the price value, convert it to double, then multiply it with 100 and then typecast it to an integer. When the price is "33.30", after converting it to double it remains 33.3 (obviously...), but after multiplying it with 100, it becomes 3329.9999999999995, and when I cast it to integer by applying simple cast operator "(int) (price * 100) ", it becomes 3329. Right now I have no idea why this is happening. So I thought may be you guys can help :) .

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• Having an @ inside of a string - PHP

  - by Msencenb

  So I know that you use a backslash to escape most things in php however the @ symbol is an operator that suppresses error messages. I'm trying to put an email string like this inside of an array "[email protected]", however php is throwing an error. How do you escape the @ sign? EDIT: Here is the code example that was throwing the error: $arr = array(3=> "[email protected]",4=> "[email protected]"); However replacing the double quotes with single quotes fixes the error as answered below.... why is that true?

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• In SQL, we can use "Union" to merge two tables. What are different ways to do "Intersection"?

  - by Jian Lin

  In SQL, there is an operator to "Union" two tables. In an interview, I was told that, say one table has just 1 field with 1, 2, 7, 8 in it, and another table also has just 1 field with 2, and 7 in it, how do I get the intersection. I was stunned at first, because I never saw it that way. Later on, I found that it is actually a "Join" (inner join), which is just select * from t1, t2 where t1.number = t2.number (although the name "join" feels more like "union" rather than "intersect") another solution seems to be select * from t1 INTERSECT select * from t2 but it is not supported in MySQL. Are there different ways to get the intersection besides these two methods?

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• Consing lists with user-defined type in Haskell

  - by user1319603

  I have this type I defined myself: data Item = Book String String String Int -- Title, Author, Year, Qty | Movie String String String Int -- Title, Director, Year, Qty | CD String String String Int deriving Show -- Title, Artist, Year, Qty I've created an empty list all_Items = [] With the following function I am trying to insert a new book of type Item (Book) into the all_Items addBook all_Items = do putStrLn "Enter the title of the book" tit <- getLine putStrLn "Enter the author of the book" aut <- getLine putStrLn "Enter the year this book was published" yr <- getLine putStrLn "Enter quantity of copies for this item in the inventory" qty <- getLine Book tit aut yr (read qty::Int):all_Items return(all_Items) I however am receiving this error: Couldn't match expected type `IO a0' with actual type `[a1]' The error points to the line where I am using the consing operator to add the new book to the list. I can gather that it is a type error but I can't figure out what it is that I am doing wrong and how to fix it. Thanks in Advance!

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• Objective c key path operators @avg,@max .....

  - by davide

  arr = [[NSMutableArray alloc]init]; [arr addObject:[NSNumber numberWithInt:4]]; [arr addObject:[NSNumber numberWithInt:45]]; [arr addObject:[NSNumber numberWithInt:23]]; [arr addObject:[NSNumber numberWithInt:12]]; NSLog(@"The avg = %@", [arr valueForKeyPath:@"@avg.intValue"]); This code works fine, but why? valueForKeyPath:@"@avg.intValue" is requesting (int) from each NSNumber, but we are outputting a %@ string in the log. If i try to output a decimal %d i get a number that possibly is a pointer to something. Can somebody explain why the integers become NSNumbers when i call the @avg operator?

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• Matching of tuples

  - by Jack

  From what I understood I can use pattern-matching in a match ... with expression with tuples of values, so something like match b with ("<", val) -> if v < val then true else false | ("<=", val) -> if v <= val then true else false should be correct but it gives me a syntax error as if the parenthesis couldn't be used: File "ocaml.ml", line 41, characters 14-17: Error: Syntax error: ')' expected File "ocaml.ml", line 41, characters 8-9: Error: This '(' might be unmatched referring on first match clause.. Apart from that, can I avoid matching strings and applying comparisons using a sort of eval of the string? Or using directly the comparison operator as the first element of the tuple?

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• Boost::Container::Vector with Enum Template Argument - Not Legal Base Class

  - by CuppM

  Hi, I'm using Visual Studio 2008 with the Boost v1.42.0 library. If I use an enum as the template argument, I get a compile error when adding a value using push_back(). The compiler error is: 'T': is not a legal base class and the location of the error is move.hpp line 79. #include <boost/interprocess/containers/vector.hpp> class Test { public: enum Types { Unknown = 0, First = 1, Second = 2, Third = 3 }; typedef boost::container::vector<Types> TypesVector; }; int main() { Test::TypesVector o; o.push_back(Test::First); return 0; } If I use a std::vector instead it works. And if I resize the Boost version first and then set the values using the [] operator it also works. Is there some way to make this work using push_back()?

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• Sort CMap Key by String Length

  - by Yan Cheng CHEOK

  Previously, I am using STL map to perform the mentioned task. struct ltstr { bool operator()(std::string s1, std::string s2) const { const int l1 = s1.length(); const int l2 = s2.length(); if (l1 == l2) { // In alphabetical order. return s1.compare(s2) < 0; } // From longest length to shortest length. return l1 > l2; } }; std::map<std::string, int, ltstr> m; How can I perform the same task using CMap? // How to make key sorted by string length? CMap<CString, LPCTSTR, int, int> m;

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• Is this call to a function object inlined?

  - by dehmann

  In the following code, Foo::add calls a function via a function object: struct Plus { inline int operator()(int x, int y) const { return x + y; } }; template<class Fct> struct Foo { Fct fct; Foo(Fct f) : fct(f) {} inline int add(int x, int y) { return fct(x,y); // same efficiency adding directly? } }; Is this the same efficiency as calling x+y directly in Foo::add? In other words, does the compiler typically directly replace fct(x,y) with the actual call, inlining the code, when compiling with optimizations enabled?

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• java.io in debian

  - by Stig

  Hello, i try to compile a java program but in the import section of the code fails: import java.net.; import java.io.; import java.util.; import java.text.; import java.awt.; //import java.awt.image.; import java.awt.event.; //import java.awt.image.renderable.; import javax.swing.; import javax.swing.border.; //import javax.swing.border.EtchedBorder; //import javax.media.jai.; //import javax.media.jai.operator.; //import com.sun.media.jai.codec.; //import java.lang.reflect.; how can i fix the problem in a linux debian machine?. Thanks

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• What are the differences between these three patterns of "class" definitions in JavaScript?

  - by user1889765

  Are there any important/subtle/significant differences under the hood when choosing to use one of these three patterns over the others? And, are there any differences between the three when "instantiated" via Object.create() vs the new operator? The pattern that CoffeeScript uses when translating "class" definitions: Animal = (function() { function Animal(name) { this.name = name; } Animal.prototype.move = function(meters) { return alert(this.name + (" moved " + meters + "m.")); }; return Animal; })(); and The pattern that Knockout seems to promote: var DifferentAnimal = function(name){ var self = this; self.name = name; self.move = function(meters){ return alert(this.name + (" moved " + meters + "m.")); }; return {name:self.name, move:self.move}; } and The pattern that Backbone promotes: var OneMoreAnimal= ClassThatAlreadyExists.extend({ name:'', move:function(){} });

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• rails - Redirecting console output to a file

  - by egarcia

  On a bash console, if I do this: cd mydir ls -l > mydir.txt The operator captures the standard input and redirects it to a file; so I get the listing of files in mydir.txt instead of in the standard output. Is there any way to do something similar on the rails console? I've got a ruby statement that generates lots of prints (~8k lines) and I'd like to be able to see it completely, but the console only "remembers" the last 1024 lines or so. So I thought about redirecting to a file - If anyone knows a better option, I'm all ears.

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• When does ref($variable) return 'IO'?

  - by Zaid

  Here's the relevant excerpt from the documentation of the ref function: The value returned depends on the type of thing the reference is a reference to. Builtin types include: SCALAR ARRAY HASH CODE REF GLOB LVALUE FORMAT IO VSTRING Regexp Based on this, I imagined that calling ref on a filehandle would return 'IO'. Surprisingly, it doesn't: use strict; use warnings; open my $fileHandle, '<', 'aValidFile'; close $fileHandle; print ref $fileHandle; # prints 'GLOB', not 'IO' perlref tries to explain why: It isn't possible to create a true reference to an IO handle (filehandle or dirhandle) using the backslash operator. The most you can get is a reference to a typeglob, which is actually a complete symbol table entry [...] However, you can still use type globs and globrefs as though they were IO handles. In what circumstances would ref return 'IO' then?

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• How do you get the logical xor of two variables in Python?

  - by Zach Hirsch

  How do you get the logical xor of two variables in Python? For example, I have two variables that I expect to be strings. I want to test that only one of them contains a True value (is not None or the empty string): str1 = raw_input("Enter string one:") str2 = raw_input("Enter string two:") if logical_xor(str1, str2): print "ok" else: print "bad" The ^ operator seems to be bitwise, and not defined on all objects: >>> 1 ^ 1 0 >>> 2 ^ 1 3 >>> "abc" ^ "" Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unsupported operand type(s) for ^: 'str' and 'str'

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• visual studio intellisense error

  - by rakkarage

  template <typename T> class Test { friend Test<T> & operator * (T lhs, const Test<T> & rhs) { Test<T> r(rhs); // return r *= lhs; } } 4 IntelliSense: identifier "T" is undefined why is T defined on line 3 but not line 4? i mean i guess its not a real error just an intellisense error... it works anyway but is there something wrong? can i fix it? or remove the red squiggles somehow? thanks i am using visual studio 2010... i wonder if this happens in other versions as well?

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• is this a simple monad example?

  - by zcaudate

  This is my attempt to grok monadic functions after watching http://channel9.msdn.com/Shows/Going+Deep/Brian-Beckman-Dont-fear-the-Monads. h uses bind to compose together two arbitrary functions f and g. What is the unit operator in this case? ;; f :: int - [str] ;; g :: str = [keyword] ;; bind :: [str] - (str - [keyword]) - [keyword] ;; h :: int - [keyword] (defn f [v] (map str (range v))) (defn g [s] (map keyword (repeat 4 s))) (defn bind [l f] (flatten (map f l))) (f 8) ;; = (0 1 2 3 4 5 6 7) (g "s") ;; = (:s :s :s :s) (defn h [v] (bind (f v) g)) (h 9) ;; = (:0 :0 :0 :0 :1 :1 :1 :1 :2 :2 :2 :2 :3 :3 :3 :3 :4 :4 :4 :4 :5 :5 :5 :5)

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• Inserting into an Associative array?

  - by RedShft

  I'm playing around with associative arrays right now and I can't seem to figure out how to add additional objects to the array. I tried insert but it doesn't recognize both arguments. Also, if I do this it produces an error: Node[bool] test; Node node; Node[bool] temp = [ false:node ]; test ~= temp; //Error 1 Error: cannot append type Node[bool] to type //Node[bool] C:\Users\CP\Documents\Visual Studio //2010\Projects\D\STDS\NPC.d 256 Does this mean you can't use the append operator on associative arrays ?

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• File::GlobMapper doesnt seem to be exporting globmap

  - by justintime

  The following is pretty well copied from the documentation. use File::GlobMapper qw( globmap ); for my $pair (globmap '<*.tar.gz>' => '<#1.tgz>' ) { } And it gives String found where operator expected at globmapper_test1.pl line 4, near "globmap '<*.tar.gz>'" (Do you need to predeclare globmap?) (Using ActivePerl 5.10.0 on Windows) Side questions - if GlobMapper only exports one function, why is it set so you have to export it explicitly?

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• Problem of using cin twice.

  - by gc

  Here is the code: string str; cinstr; cout<<"first input:"<<str<<endl; getline(cin, str); cout<<"line input:"<<str<<endl; The result is that getline never pauses for user input, therefore the second output is always empty. After spending some time on it, I realized after the first call "cinstr", it seems '\n' is still stored in cin (using cin.peek() to check), which ends getline immediately. The solution will be adding one more line between the first usage and the second one: cin.ignore(numeric_limits::max(), '\n'); However, I still don't understand, why is '\n' left there after the first call? What does istream& operator really do?

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• Template type deduction with a non-copyable class

  - by Evan Teran

  Suppose I have an autolocker class which looks something like this: template <T> class autolocker { public: autolocker(T *l) : lock(l) { lock->lock(); } ~autolocker() { lock->unlock(); } private: autolocker(const autolocker&); autolocker& operator=(const autolocker&); private: T *lock; } Obviously the goal is to be able to use this autolocker with anything that has a lock/unlock method without resorting to virtual functions. Currently, it's simple enough to use like this: autolocker<some_lock_t> lock(&my_lock); // my_lock is of type "some_lock_t" but it is illegal to do: autolocker lock(&my_lock); // this would be ideal Is there anyway to get template type deduction to play nice with this (keep in my autolocker is non-copyable). Or is it just easiest to just specify the type?

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• VS 2008 linking error

  - by AvatarBlue

  I'm using Visual Studio 2008 C++ and working on a dll project. Debug compiled and linked perfectly but when I compile the release version, it shows this: VImgPtr.obj : error LNK2001: unresolved external symbol @__security_check_cookie@4 VLibraryPtr.obj : error LNK2001: unresolved external symbol "void __cdecl operator delete[](void *)" (??_V@YAXPAX@Z) D:\Source Code\VImgLib\Release-vc9u\VImgLib-vc9u.dll : fatal error LNK1120: 2 unresolved externals If I selected Multi-threaded (/MT) in "C/C++-Code Generation tab), it linked ok. The problem is only when I choose Multi-threaded DLL (/MD). I'm releasing a dll, so should be /MD right?

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• Aggregate functions in ANSI SQL

  - by morpheous

  I want to use multiple aggregate functions in a query. All the examples i have seem on aggregate functions however, are trivial. Typically, they are of the form: SELECT field1,agg_func1, agg_func2 GROUP BY SOME_COLUMNS HAVING agg_func1 OP SOME_SCALAR Where: OP: is a boolean operator (e.g. <, = etc) SOME_SCALAR: is a scalar (i.e. a constant number) What I want to know is if it is possible to write (IN ANSI SQL) queries like: SELECT field1,agg_func1, agg_func2, agg_func3 GROUP BY SOME_COLUMNS HAVING (agg_func1 OP1 agg_func2) OP2 (agg_func2 OP3 agg_func3) Where: OP[N] are boolean operators or ANSI SQL clause operators like 'BETWEEN', 'LIKE', 'IN' etc. Also, assuming this is possible (I have not seen any documentation saying otherwise) are there any efficiency/performance considerations (i.e. penalties) when the HAVING clause consists of a boolean expression combining the output of the aggregate functions - instead of the normal comparison of the output of the aggregate with a constant number (e.g. min('salary') 100 ) - which is often used in the most banal examples involving aggregate functions?

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