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  • Compile time string hashing

    - by Caspin
    I have read in few different places that using c++0x's new string literals it might be possible to compute a string's hash at compile time. However, no one seems to be ready to come out and say that it will be possible or how it would be done. Is this possible? What would the operator look like? I'm particularly interested use cases like this. void foo( const std::string& value ) { switch( std::hash(value) ) { case "one"_hash: one(); break; case "two"_hash: two(); break; /*many more cases*/ default: other(); break; } } Note: the compile time hash function doesn't have to look exactly as I've written it. I did my best to guess what the final solution would look like, but meta_hash<"string"_meta>::value could also be a viable solution.

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  • How do I get Linq-to-SQL to refresh its local copy of a database record?

    - by Gary McGill
    Suppose I have an Orders table in my database and a corresponding model class generated by the VS2008 "Linq to SQL Classes" designer. Suppose I also have a stored procedure (ProcessOrder) in my database that I use to do some processing on an order record. If I do the following: var order = dataContext.Orders.Where(o => o.id == orderId).First(); // More code here dataContext.ProcessOrder(orderId); order.Status = "PROCESSED"; dataContext.SubmitChanges(); ...then I'll get a concurrency violation if the ProcessOrder stored proc has modified the order (which is of course very likely), because L2S will detect that the order record has changed, and will fail to submit the changes to that order. That's all fairly logical, but what if I want to update the order record after calling the stored proc? How do I tell L2S to forget about its cached copy and refresh it from the DB?

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  • Linq to sql translation to sql of custom method

    - by DJPB
    hi there is there a way to translate an expression to sql to use with linq to sql? for example I have a method that compares two values example: MyComparer.Compare(value1, value2, ">") return value1 > value2 MyComparer.Compare(value1, value2, "=") return value1 == value2 MyComparer.Compare(value1, value2, "<=") return value1 <= value2 and i would like a query like var list = from i in dataContext.items where MyComparer.Compare(i.value, someValue, "some operator") select ... this won't work because, obviously, MyComparer doesn't translate to sql maybe this is a twisted question, but how can i translate this method to sql or is this possible? tks

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  • Should I worry about reigning in namespace number/length/scope?

    - by Jay
    I've recently reorganized a solution-in-progress from 24 projects to 4. To keep the copious files organized in the "main" project, things are in folders in folders in folders. I think I've preserved a logical, discoverable arrangement of the solution content. As a result, of course, I end up with namespaces like AppName.DataAccess.NHibernate.Fluent.Mappings. Is there any compelling reason that I should care about flattening out the namespace hierarchy when my project has a somewhat deeply nested folder structure? (I am not concerned about resolving or managing using directives; I let ReSharper do all the heavy lifting here.)

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  • Load binary file using fstream

    - by Kirill V. Lyadvinsky
    I'm trying to load binary file using fstream in the following way: #include <iostream #include <fstream #include <iterator #include <vector using namespace std; int main() { basic_fstream<uint32_t file( "somefile.dat", ios::in|ios::binary ); vector<uint32_t buffer; buffer.assign( istream_iterator<uint32_t, uint32_t( file ), istream_iterator<uint32_t, uint32_t() ); cout << buffer.size() << endl; return 0; } But it doesn't work. In Ubuntu it crashed with std::bad_cast exception. In MSVC++ 2008 it just prints 0. I know that I could use file.read to load file, but I want to use iterator and operator>> to load parts of the file. Is that possible? Why the code above doesn't work?

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  • Hibernate advanced select

    - by Marcus
    We want to get a row from a table using Hibernate a la: select max(id) from mytable where date = <date> Then select * from mytable where id = <max_id> We are currently using Hibernate to map mytable to Java domain objects. I know how to load the domain object based on an id. So I could just do #1 using JDBC and then load the domain object using Hibernate the "normal" way. But.. is there a way to do this with one single Hibernate logical query?

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  • Java 'Prototype' pattern - new vs clone vs class.newInstance

    - by Guillaume
    In my project there are some 'Prototype' factories that create instances by cloning a final private instance. The author of those factories says that this pattern provides better performance than calling 'new' operator. Using google to get some clues about that, I've found nothing really relevant about that. Here is a small excerpt found in a javdoc from an unknown project javdoc from an unknown project Sadly, clone() is rather slower than calling new. However it is a lot faster than calling java.lang.Class.newInstance(), and somewhat faster than rolling our own "cloner" method. For me it's looking like an old best practice of the java 1.1 time. Does someone know more about this ? Is this a good practice to use that with 'modern' jvm ?

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  • Java swing examples - Ants running around a world getting food from piles?

    - by Charlie
    I haven't done any swing programming in a while, so I'm looking for some GUI examples that are at least close to what I'm trying to do. The gui that I'll need to be representing is small nodes (let's say ants) travelling around collecting food from food piles (which just means small nodes travelling to bigger nodes). Once the node (ant) takes a piece of food, the pile shrinks a bit and the ant takes it back home (to ANOTHER circle). This SOUNDS pretty trivial, but all of the boilerplate involved in setting up a java GUI just makes little logical sense to me, and the GUI is such a small piece of my project. Any examples that would be great for this style of project would be greatly appreciated. Thanks!

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  • Recommend a PHP framework for new PHP programmer

    - by webworm
    Hi All, I am fairly new to PHP but not programming in general. I was hoping I could get some suggestions on the best type of PHP framework to start with considering my basic experience with PHP. I have a .NET and ASP.NET background and I am familiar with the MVC design pattern. I would prefer to start with a framework that makes logical design easier but does not generate all the code for you. I have read some like the Zend framework for this. Opinions?

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  • C# switch: case not falling through to other cases limitation

    - by Mike Fielden
    This question is kind of an add-on to this question In C#, a switch case cannot fall through to other cases, this causes a compilation error. In this case I am just adding some number to the month total for the selected month and each subsequent month thereafter. (simple example, not meant to be real) switch (month) { case 0: add something to month totals case 1: add something to month totals case 2: add something to month totals default: break; } Is there a logical alternative to this in C# without having to write out a ton of if statements? if (month <= 0) add something to month if (month <= 1) add something to month if (month <= 2) add something to month .... etc

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  • How do I copy object in Qt?

    - by Martin
    I'm using Qt and have some real basic problems. I have created my own widget MyTest that have a variable obj. I need to set this variable obj from an object outside of the widget so that the variable is copied not just a pointer to another object. I get an error message and can't figure out how to do this basic stuff. This is the code I'm using: MyTest.h: class MyTest : public QWidget { Q_OBJECT public: void setObj(QObject &inobj); QObject obj; .... } MyTest.cpp: void MyTest::setObj(QObject &inobj) { obj = inobj; //HERE I get the error message: "illegal access from 'QObject' to protected/private member 'QObject::operator=(const QObject &)'" } main.cpp: int main(int argc, char *argv[]) { QApplication a(argc, argv); QObject *ob = new QObject(); MyTest w; w.setObj(*ob); } Thanks for your help!

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  • How to make Databinding type safe and support refactoring

    - by Ian Ringrose
    When I wish to bind a control to a property of my object, I have to provide the name of the property as a string. This is not very good because: If the property is removed or renamed, I don’t get a compiler warning. If a rename the property with a refactoring tool, it is likely the data binding will not be updated. I don’t get an error until runtime if the type of the property is wrong, e.g. binding an integer to a date chooser. Is there a design-paten that gets round this, but still has the ease of use of data-binding? (This is a problem in WinForm, Asp.net and WPF and most likely lots of other systems) I have now found "workarounds for nameof() operator in C#: typesafe databinding" that also has a good starting point for a solution.

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  • Current state of client-side XSLT

    - by Casey
    Last I heard, Blizzard was one of the few companies to put client-side XSLT into practice (2008). Is this still the case in 2011, or are more people now exploring this technique in production?  It seems that modern browsers (IE9, FF4, Chrome) and client processing power are primed to exploit this standard for tangible savings in server CPU power and bandwidth on large scale properties. Am I missing something? The negative aspects I'm aware of include * additional rendering time * additional assets required on uncached page load * additional layer of complexity * noticably less developer experience than server-side template techniques The benefits I perceive include * distributed template composition (offloaded on the client) * caching of common template fragments offloaded on the client * logical separation of document structure and data * well-documented web standard supported by all modern browsers Finally, although I know it's impossible to predict the future, I am curious to know opinions on whether or not client-side XSLT's day will come. With interest in HTML5 driving users to upgrade their browsers and developers to explore new techniques, I would say yes. How about you? Thanks in advance, Casey

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  • Practical differences between classes and structs in .net (not conceptual)?

    - by Gulshan
    Whenever I tried to search about differences between classes and structs in C# or .net, I ended up with the conceptual overview of the two things like value type or the reference type, where the variables are allocated etc. But I need some practical differences. I have found some like different behavior of assignment operator, having constructors etc. Can anybody provide some more practical differences which will be directly useful while coding? Like the things works with one but not with other or same operation showing different behavior. And some common mistakes regarding these two. Also please suggest where to consider using a struct instead of a class. And where the structs should not be used.

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  • R: ggplot2, how to add a number of layers to a plot at once to reduce code

    - by John
    library(ggplot2) This code produces a nice looking plot: qplot(cty, hwy, data = mpg, colour = displ) + scale_y_log2() + labs(x="x axis") + labs(y="y axis") + opts(title = "my title") But I want to setup variables to try and to reduce code repetition: log_scale <- scale_y_log2() xscale <- labs(x="x axis") yscale <- labs(y="y axis") title <- opts(title = "my title") my_scales <- c(log_scale, xscale, yscale, title) # make a variable to hold the scale info changes above So that I can do this and add a bunch of things at the same time: qplot(cty, hwy, data = mpg, colour = displ) + my_scales # add these to your plot. but I get this error: Error in object$class : $ operator is invalid for atomic vectors I realize that the things going into my_scales need to be layers / different types of objects, but I don't see what they should be.

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  • Prevent SQL injection from form-generated SQL.

    - by Markos Fragkakis
    Hi all, I have a search table where user will be able to filter results with a filter of the type: Field [Name], Value [John], Remove Rule Field [Surname], Value [Blake], Remove Rule Field [Has Children], Value [Yes], Remove Rule Add Rule So the user will be able to set an arbitrary set of filters, which will result essentially in a completely dynamic WHERE clause. In the future I will also have to implement more complicated logical expressions, like Where (name=John OR name=Nick) AND (surname=Blake OR surname=Bourne), Of all 10 fields the user may or may not filter by, I don't know how many and which filters the user will set. So, I cannot use a prepared statement (which assumes that at least we know the fields in the WHERE clause). This is why prepared statements are unfortunately out of the question, I have to do it with plain old, generated SQL. What measures can I take to protect the application from SQL Injection (REGEX-wise or any other way)?

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  • Error while excuting a simple boost thread program

    - by Eternal Learner
    Hi All, Could you tell mw what is the problem with the below boost::thread program #include<iostream> #include<boost/thread/thread.hpp> boost::mutex mutex; class A { public: A() : a(0) {} void operator()() { boost::mutex::scoped_lock lock(mutex); } private: int a; }; int main() { boost::thread thr1(A()); boost::thread thr2(A()); thr1.join(); thr2.join(); } I get the error message: error: request for member 'join' in 'thr1', which is of non-class type 'boost::thread()(A ()())' BoostThread2.cpp:30: error: request for member 'join' in 'thr2', which is of non-class type 'boost::thread ()(A ()())'

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  • Autotesting a network interface

    - by Machado
    Hi All, I'm developing a software component responsible for testing if a network interface has conectivity with the internet. Think of it as the same test the XBOX360 does to inform the user if it's connected with the Live network (just as an example). So far I figured the autotest would run as this: 1) Test the physical network interface (if the cable is conected, has up/downlink, etc...) 2) Test the logical network (has IP address, has DNS, etc...) 3) Connects to the internet (can access google, for example) 4) ??? 5) Profit! (just kidding...) My question relates to step 3: How can I detect, correctly, if my software has connection with the internet ? Is there any fixed IP address to ping ? The problem is that I don't want to rely solely on google.com (or any other well-known address), as those can change in time, and my component will be embbeded on a mobile device, not easy to update. Any suggestions ?

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  • varchar comparison in SQL Server

    - by Ram
    I am looking for some SQL varchar comparison function like C# string.compare (we can ignore case for now, should return zero when the character expression are same and a non zero expression when they are different) Basically I have some alphanumeric column in one table which needs to be verified in another table. I cannot do select A.col1 - B.col1 from (query) as "-" operator cannot be applied on character expressions I cannot cast my expression as int (and then do a difference/subtraction) as it fails select cast ('ASXT000R' as int) Conversion failed when converting varchar 'ASXT000R' to int Soundex would not do it as soundex is same for 2 similar strings Difference would not do it as select difference('abc','ABC') = 4 (as per msdn, difference is the difference in the soundex of 2 character expressions and difference =4 implies least different) Is there any other way of doing it ?

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  • LINQ and set difference

    - by Pierre
    I have two collections a and b. I would like to compute the set of items in either a or b, but not in both (a logical exclusive or). With LINQ, I can come up with this: IEnumerable<T> Delta<T>(IEnumerable<T> a, IEnumerable<T> b) { return a.Except (b).Union (b.Except (a)); } I wonder if there are other more efficient or more compact ways of producing the difference between the two collections.

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  • Understanding the "Instantiation" of Actionscript/Flash Objects

    - by parallax7d
    Could someone expand and clarify the different logical instantiations of objects in actionscript? So far it seems there are 3 layers of instantiations, for lack of a better term. The first one is declaring a variable/type. Next is instantiating that variable with something solid in the code, like a method or function? Is this just a way to glue things together? Then after that you instantiate it on the stage, is this something you have to do explicitly, or is it a side effect? Is this "3 layer" concept the correct way of looking at it, kind of like the MVC for flash app logic?

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  • LINQ Quicksort is Unstable Except When Cascading

    - by Mystagogue
    On page 64 of "LINQ To Objects Using C# 4.0" (Tony Magennis) he states that LINQ's quicksort ordering algorithm is unstable... ...although this is simply solved by cascading the result into a ThenBy or ThenByDescending operator. Huh? Why would cascading an unstable sortation into another sortation fix the result? In fact, I'd say that isn't possible. The original order, once passed through an unstable sort, is simply lost. What am I missing here?

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  • static arrays defined with unspecified size, empty brackets?

    - by ahmadabdolkader
    For the C++ code fragment below: class Foo { int a[]; // no error }; int a[]; // error: storage size of 'a' isn't known void bar() { int a[]; // error: storage size of 'a' isn't known } why isn't the member variable causing an error too? and what is the meaning of this member variable? I'm using gcc version 3.4.5 (mingw-vista special) through CodeBlocks 8.02. On Visual Studio Express 2008 - Microsoft(R) C/C++ Optimizing Compiler 15.00.30729.01 for 80x86, I got the following messages: class Foo { int a[]; // warning C4200: nonstandard extension used : zero-sized array in struct/union - Cannot generate copy-ctor or copy-assignment operator when UDT contains a zero-sized array }; int a[]; void bar() { int a[]; // error C2133: 'a' : unknown size } Now, this needs some explaination too.

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