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  • sql boolean truth test: zero OR null

    - by AK
    Is there way to test for both 0 and NULL with one equality operator? I realize I could do this: WHERE field = 0 OR field IS NULL But my life would be a hundred times easier if this would work: WHERE field IN (0, NULL) (btw, why doesn't that work?) I've also read about converting NULL to 0 in the SELECT statement (with COALESCE). The framework I'm using would also make this unpleasant. Realize this is oddly specific, but is there any way to test for 0 and NULL with one WHERE predicate?

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  • I want to retrieve some information based on Caller ID

    - by Hassan Al-Jeshi
    Hello, my friend has a Real Estate company that receives a lot of phone calls everyday. He wants to have a solution such that when somebody call to his company, the operator sees all the information about the person who is calling based on the database he have right now and the caller ID. Is there a ready made software or solution that can do the job?? Since I'm a software engineer myself, I would never mind developing something from scratch or built on a ready made system (with a team of course), but I need some direction on how to start?? Notes: 1- cost is not an issue 2- the customers database is there but we never mind replacing it in a format to suit the new solution Best Regards,

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  • Why does a Linq Cast<T> operation fail when I have an implicit cast defined?

    - by Ryan Versaw
    I've created two classes, with one of them having an implicit cast between them: public class Class1 { public int Test1; } public class Class2 { public int Test2; public static implicit operator Class1(Class2 item) { return new Class1{Test1 = item.Test2}; } } When I create a new list of one type and try to Cast<T> to the other, it fails with an InvalidCastException: List<Class2> items = new List<Class2>{new Class2{Test2 = 9}}; foreach (Class1 item in items.Cast<Class1>()) { Console.WriteLine(item.Test1); } This, however, works fine: foreach (Class1 item in items) { Console.WriteLine(item.Test1); } Why is the implicit cast not called when using Cast<T>?

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  • How to force a deep copy when copying structs with arrays?

    - by Danvil
    If have a struct A { public double[] Data; public int X; } How can I force a deep copy when using operator= or adding instances of A to a container? The problem is for example: A a = new A(); var list = new List<A>(); list.Add(a); // does not make a deep copy of Data A b = a; // does not make a deep copy of Data Do I really have to implement my own DeepClone method and call it every time? This would be extremly error-prone ...

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  • Why exactly is calling the destructor for the second time undefined behavior in C++?

    - by sharptooth
    As mentioned in this answer simply calling the destructor for the second time is already undefined behavior 12.4/14(3.8). For example: class Class { public: ~Class() {} }; // somewhere in code: { Class* object = new Class(); object->~Class(); delete object; // UB because at this point the destructor call is attempted again } In this example the class is designed in such a way that the destructor could be called multiple times - no things like double-deletion can happen. The memory is still allocated at the point where delete is called - the first destructor call doesn't call the ::operator delete() to release memory. For example, in Visual C++ 9 the above code looks working. Even C++ definition of UB doesn't directly prohibit things qualified as UB from working. So for the code above to break some implementation and/or platform specifics are required. Why exactly would the above code break and under what conditions?

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  • T-SQL Operations on a Calculated Date Field

    - by firedrawndagger
    Can I do WHERE operations on a calculated date field? I have a lookup field, which has been written badly in SQL and unfortunately I can't change it. But basically it stores dates as characters such as "July-2010" or "June-2009" (along with other non date data). I want to extract the dates first (which I did using a LIKE opertor) and then extract data based on a date range. SELECT BusinessUnit, Lookup, ReleaseDate FROM ( SELECT TOP 10 LookupColumn As Lookup, BU as BusinessUnit, CONVERT(DATETIME, REPLACE(LookupColumn,'-',' ')) as ReleaseDate FROM [dbo].[LookupTable] WHERE LookupColumn LIKE N'%-2010' ) MyTable ORDER BY ReleaseDate WHERE ReleaseDate = '2010-02-01' I'm having issues with WHERE operator. I would assume creating a subquery to encapsulate the calculated field would allow me to do operations with it such as WHERE but maybe I'm wrong. Bottom line is it possible to do operations on calculated fields?

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  • Storing expression template functors

    - by UncaughtException
    Hello guys, at the moment I'm really interested in expression templates and want to code a library for writing and differentiating mathematical functions with a lambda-style syntax. At the moment, I'm able to write (_x * _x)(2); and get the correct result 4. But I would really like to do something like MathFunction f = _x * _x; f(2);, but I don't have any ideas on how to cope with the recursive expression templates on the right side. Is it possible to achieve this without using the 'auto'-Keyword instead of MathFunction or having to make the operator() virtual? Thanks for your help!

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  • C++: conjunction of binds?

    - by Helltone
    Suppose the following two functions: #include <iostream> #include <cstdlib> // atoi #include <cstring> // strcmp #include <boost/bind.hpp> bool match1(const char* a, const char* b) { return (strcmp(a, b) == 0); } bool match2(int a, const char* b) { return (atoi(b) == a); } Each of these functions takes two arguments, but can be transformed into a callable object that takes only one argument by using (std/boost)bind. Something along the lines of: boost::bind(match1, "a test"); boost::bind(match2, 42); I want to be able to obtain, from two functions like these that take one argument and return bool, a callable object that takes two arguments and returns the && of the bools. The type of the arguments is arbitrary. Something like an operator&& for functions that return bool.

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  • Does std::multiset guarantee 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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  • Is there a shorthand way to denullify a string in C#?

    - by Moose Factory
    Is there a shorthand way to denullify a string in C#? It would be the equivalent of (if 'x' is a string): string y = x == null ? "" : x; I guess I'm hoping there's some operator that would work something like: string y = #x; Wishful thinking, huh? The closest I've got so far is an extension method on the string class: public static string ToNotNull(this string value) { return value == null ? "" : value; } which allows me to do: string y = x.ToNotNull(); Any improvements on that, anyone?

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  • Why isn't Perl's File::GlobMapper 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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  • Using pipes inside a class in C++

    - by Paul
    I'm trying to use this tutorial to make plots with Gnuplot in C++. However I will be using the pipe to Gnuplot from within a class, but then I run into some problems: I've got a header file where I declare all variables etc. I need to declare the pipe-variable here too, but how do I do that? I've tried doing it straight away, but it doesn't work: Logger.h: class Logger { FILE pipe; } Logger.cpp: Logger::Logger() { //Constructor *pipe = popen("gnuplot -persist","w"); } Gives the error Logger.cpp:28: error: no match for ‘operator=’ in ‘*((Logger*)this)->Logger::pipe = popen(((const char*)"gnuplot -persist"), ((const char*)"w"))’ Suggestions?

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  • Force an object to be allocated on the heap

    - by Warren Seine
    A C++ class I'm writing uses shared_from_this() to return a valid boost::shared_ptr<>. Besides, I don't want to manage memory for this kind of object. At the moment, I'm not restricting the way the user allocates the object, which causes an error if shared_from_this() is called on a stack-allocated object. I'd like to force the object to be allocated with new and managed by a smart pointer, no matter how the user declares it. I thought it could be done through a proxy or an overloaded new operator, but I can't find a proper way of doing that. Is there a common design pattern for such usage? If it's not possible, how can I test it at compile time?

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  • C++ Word-Number to int

    - by Andrew
    I'm developing a program that makes basic calculations using words instead of numbers. E.g. five + two would output seven. The program becomes more complex, taking input such as two_hundred_one + five_thousand_six (201 + 5006) Through operator overloading methods, I split each number and assign it to it's own array index. two would be [0], hundred is [1], and one is [2]. Then the array recycles for 5006. My problem is, to perform the actual calculation, I need to convert the words stored in the array to actual integers. I have const string arrays such as this as a library of the words: const string units[] = { "", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" }; const string teens[] = { "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen" }; const string tens[] = { "", "", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety" }; If my 'token' array has stored in it two hundred one in index 0, 1, and 2, I'm not sure what the best way to convert these to ints would involve.

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  • Revamping an old and unstable IT-solution for a customer?

    - by cmbrnt
    I've been given the cumbersome task to totally redo the IT-infrastructure for a customer's office. They are currently running Windows XP all over, with one computer acting as a file server with no control over which users have access to which files, and so on. To top it off, this file server also functions as a workstation, which means it gets rebooted every time the user notices some sluggish behavior or experiences problems with flash games. To say the least, this isn't working for them. Now - I've got a very slim budget, but I need to set up a new server, and I wish to run Windows Server 2008 on it. I also need the ability to access the network remotely via VPN. Would it be a good idea to install VMware ESXi 4.1 onto the new server, and then run Windows Server 2008 as well as a separate Debian install for openvpn on it? I don't like the Domain Controller for the future AD to also run a VPN-server, because of stability issues when something goes to hell with either of them. There will be no redundancy though. However, I'm not sure if there is something to gain by installing a VPN solution on the Windows Server itself, when it comes to accessing file shares on the network via VPN. I don't know how to enable users logging in via the VPN to access the remote files, since they will be accessing the network from their own home computers (which is indeed a really bad idea, but this is what I've got to work with). They won't be logged in to the windows Domain, but rather their home workgroups. I need to be able to grant access to files in certain directories based on the logged in AD-user, but every computer won't necessarily be configured to log into the domain. I'm not sure how to explain this in a good way, but I'd be happy to clarify if somethings not clear. Any help would be great, because I've got a feeling that I can't do this without introducing a bunch of costly new rules when it comes to their IT-solution. I'd rather leave that untouched and go on my merry way to the next assignment.

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  • ILNumerics multiply complex with matrix<double>

    - by nik
    I m looking at ILNumerics to translate some matlab code into c#. How would I multiply a complex and a double? Simplified description: In Matlab: A=[1 2 3] i*A*A' Returns a complex number. How would I do the same in ILNumerics: ILArray<double> A = ILMath.array(1.0, 2.0, 3.0); complex B = complex.i * ILMath.multiply(A,A.T); Throws the error: Operator '*' cannot be applied to operands of type 'ILNumerics.complex' and 'ILNumerics.ILRetArray<double>' Update This works: double C = 14.0; complex D = complex.i * C; But shouldnt: ILMath.multiply(A,A.T) also return 14.0?

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  • MySQL Join Comma Separated Field

    - by neeraj
    I have two tables. First Table is a batch table that contain comma separated student id in field "batch" batch -------------- id batch -------------- 1 1,2 2 3,4 Second Table is marks marks ---------------------- id studentid subject marks 1 1 English 50 2 2 English 40 3 3 English 70 4 1 Math 65 5 4 English 66 6 5 English 75 7 2 Math 55 How we can find those students of first batch id =1 who have scored more than 45 marks in English without using sub query. Problem i found to get this done using a single query is that we can not use IN as an association operator in JOIN statement What changes are required in below query to make it work? SELECT * FROM batch INNER JOIN marks ON marks.studentid IN(batch.batch) where batch.id = 1

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  • Undefined / Uninitialized default values in a class

    - by Jir
    Let's suppose you have this class: class A { public: A () {} A (double val) : m_val(val) {} ~A () {} private: double m_val; }; Once I create an instance of A, how can I check if m_val has been initialized/defined? Put it in other words, is there a way to know if m_val has been initialized/defined or not? Something along the lines of the defined operator in Python, I suppose. (But correct me if I'm wrong.) I thought of modifying the class and the c-tors the following way: class A { public: A () : defined(false) {} A (double val) : m_val(val), defined(true) {} ~A () {} private: double m_val; bool defined; }; How do you rate this solution? Any suggestion? TIA, Chris

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  • Mixing LINQ to SQL with properties of objects in a generic list

    - by BPotocki
    I am trying to accomplish something like this query: var query = from a in DatabaseTable where listOfObjects.Any(x => x.Id == a.Id) select a; Basically, I want to filter the results where a.Id equals a property of one of the objects in the generic list "listOfObjects". I'm getting the error "Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator." Any ideas on how to filter this in an easily readable way using "contains" or another method? Thanks in advance.

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  • Glib::ustring and Japanese characters

    - by user294787
    Glib::ustring is supposed to work well with UTF8 but I have a problem when working with Japanese strings. If you compare those two strings, "???" and "???", using == operator or compare method, it will answer that those two strings are equals. I don't understand why. How Glib::ustring works ? The only way I found to get false to the comparison is to compare strings of different sizes. For example "?????" and "????". Very strange...

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  • C++ and preprocessor macro gotcha

    - by aaa
    hello. Appologies for yet another gotcha question. Can you figure out what is wrong with the statement below? gcc error states: "type name declared as function returning array". #define MACRO(a) (a)[1] class index { typedef int index_type[2]; index_type& operator[](int i); }; int k = 0; int i = MACRO(index()[k]); ps: is such questions are deemed too annoying, I am going to stop.

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  • Purpose of IF, ELSE, FOR macros ?

    - by psihodelia
    I have a source code of a library which has a lot of strange IF, ELSE, FOR, etc. macros for all common C-keywords instead of using just usual if,else,for,while keywords. These macros are defined like this: #define IF( a) if( increment_if(), a) where increment_if() function is defined so: static __inline void increment_if( void) { // If the "IF" operator comes just after an "ELSE", its counter // must not be incremented. ... //implementation } I don't really understand, what is the purpose of such macros? This library is for a real-time application and I suppose that using such macros must slow-down an application.

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  • How can I import tasks into Project that have already been started?

    - by unknown
    I am writing a feature to import tasks from an online bug tracking / project management tool into Microsoft Project, primarily for resource leveling. Currently I am importing all tasks in as Fixed work, and giving them an assignment to a single resource for 100% of the work. The duration is then dynamically calculated, which at import time is equal to the amount of work. However, I am not a project manager by any means, and am having difficulty on how to get the start dates to calculate correctly. I've never used Project either. I am using Schedule From Start and setting the Project Start Date to the date the contract was signed / work was approved. However, this can be in the past, and I do not want current tasks scheduled from that date. Should it be today then? Another problem I have is with tasks that were already started. I have remaining work set, and I was placing a constraint on them to be started on the day the work was first applied. However, the remaining work for the task would be scheduled from that date, which was sometimes in the past. Using task constraints, a project start date, and whatever other settings available to me that I don't know about, what is the correct way to have the tasks scheduled?

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  • Assigning two strings together getting Access Read Violation

    - by Jay Bell
    I am trying to pass a string to a class mutator and set the private member to that string here is the code that is sending the string void parseTradePairs(Exchange::Currency *curr, std::string *response, int begin, int exit) { int start; int end; string temp; string dataResponse; CURL *tempCurl; initializeCurl(tempCurl); int location = response->find("marketid", begin); if(location <= exit) { start = location + 11; begin = response->find("label", start); end = begin - start - 3; findStrings(start, end, temp, response); getMarketInfo(tempCurl, temp, dataResponse); curr->_coin->setExch(temp); // here is the line of code that is sending the string dataResponse >> *(curr->_coin); curr->_next = new Exchange::Currency(curr, curr->_position + 1); parseTradePairs(curr->_next, response, begin, exit); } } and here is the mutator within the coin class that is receiving the string and assigning it to _exch void Coin::setExch(string exch) { _exch = exch; } I have stepped through it and made sure that exch has the string in it. "105" but soon as it hits _exch = exch; I get the reading violation. I tried passing as pointer as well. I do not believe it should go out of scope. and the string variable in the class is initialized to zero in the default constructor but again that should matter unless I am trying to read from it instead of writing to it. /* defualt constructor */ Coin::Coin() { _id = ""; _label = ""; _code= ""; _name = ""; _marketCoin = ""; _volume = 0; _last = 0; _exch = ""; } Exchange::Exchange(std::string str) { _exch = str; _currencies = new Currency; std::string pair; std::string response; CURL *curl; initializeCurl(curl); getTradePairs(curl, response); int exit = response.find_last_of("marketid"); parseTradePairs(_currencies, &response, 0, exit); } int main(void) { CURL *curl; string str; string id; Coin coin1; initializeCurl(curl); Exchange ex("cryptsy"); curl_easy_cleanup(curl); system("pause"); return 0; } class Exchange { public: typedef struct Currency { Currency(Coin *coin, Currency *next, Currency *prev, int position) : _coin(coin), _next(next), _prev(prev), _position(position) {} Currency(Currency *prev, int position) : _prev(prev), _position(position), _next(NULL), _coin(&Coin()){} Currency() : _next(NULL), _prev(NULL), _position(0) {} Coin *_coin; Currency *_next; Currency *_prev; int _position; }; /* constructor and destructor */ Exchange(); Exchange(std::string str); ~Exchange(); /* Assignment operator */ Exchange& operator =(const Exchange& copyExchange); /* Parse Cryptsy Pairs */ friend void parseTradePairs(Currency *curr, std::string *response, int begin, int exit); private: std::string _exch; Currency *_currencies; }; here is what i changed it to to fix it. typedef struct Currency { Currency(Coin *coin, Currency *next, Currency *prev, int position) : _coin(coin), _next(next), _prev(prev), _position(position) {} Currency(Currency *prev, int position) : _prev(prev), _position(position), _next(NULL), _coin(&Coin()){} Currency() { _next = NULL; _prev = NULL; _position = 0; _coin = new Coin(); } Coin *_coin; Currency *_next; Currency *_prev; int _position; };

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