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  • C++ enforce conditions on inherited classes

    - by user231536
    I would like to define an abstract base class X and enforce the following: a) every concrete class Y that inherits from X define a constructor Y(int x) b) it should be possible to test whether two Y objects are equal. For a, one not very good solution is to put a pure virtual fromInt method in X which concrete class will have to define. But I cannot enforce construction. For b), I cannot seem to use a pure virtual method in X bool operator == (const X& other) const =0; because in overridden classes this remains undefined. It is not enough to define bool operator == (const Y& other) const { //stuff} because the types don't match. How do I solve these problems?

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  • In a C++ template, is it allowed to return an object with spesific type parameters?

    - by nieldw
    When I've got a template with certain type parameters, is it allowed for a function to return an object of this same template, but with different types? In other words, is the following allowed? template<class edgeDecor, class vertexDecor, bool dir> Graph<edgeDecor,int,dir> Graph<edgeDecor,vertexDecor,dir>::Dijkstra(vertex s, bool print = false) const { /* Construct new Graph with apropriate decorators */ Graph<edgeDecor,int,dir> span = new Graph<edgeDecor,int,dir>(); /* ... */ return span; }; If this is not allowed, how can I accomplish the same kind of thing?

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  • ASP.Net website makes browser load unwanted (non-referenced) plugins

    - by alec0001
    I've found that some of my ASP.Net web apps prompt the browser to load plugins that I'm not explicitely using and certainly haven't deliberately referenced in the project settings. Two that come to mind are for MS MediaPlayer and the "SVG Viewer for Netscape". The only commonality I've determined so far is that the two sites/apps affected both use Master pages (nested in some cases). We don't use SVG file types (just the normal mix of jpg/gif/png) and no video/audio (not yet anyway). Can anyone provide a hint as to where the references for these might be creeping in? e.g. Is it a server-level include? Or a .Net runtime default when using master pages? Does anyone else even experience this, or is it just me? No urgency, I'd just like to remove it if possible. Thanks. Al

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  • Composite pattern in C++ problem

    - by annouk
    Hello! I have to work with an application in C++ similar to a phone book: the class Agenda with an STL list of Contacts.Regarding the contacts hierarchy,there is a base-class named Contact(an abstract one),and the derived classes Friend and Acquaintance(the types of contact). These classes have,for instance, a virtual method called getName,which returns the name of the contact. Now I must implement the Composite pattern by adding another type of contact,Company(being derived from Contact),which also contains a collection of Contacts(an STL list as well),that can be either of the "leaf" type(Friends or Acquaintances),or they can be Companies as well. Therefore,Company is the Compound type. The question is: how and where can I implement an STL find_if to search the contact with a given name(via getName function or suggest me smth else) both among the "leaf"-type Contact and inside the Company collection? In other words,how do I traverse the tree in order to find possible matches there too,using an uniform function definition? I hope I was pretty clear...

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  • pound character(#) in asp.net ajax

    - by Praveen Prasad
    iam using asp.net and asp.net-ajax every thing happens on browser urls are of format http://somepage#page1 http://somepage#page2 http://somepage#page3 now all these urls are in a secured folder when logged in user directly types (or use bookmark) a url like below, he is shown that page http://somepage#page2 -- (bookmarked url lying in secured folder) now when a user user who is not logged in directly type above url he gets redirected to login page but on login page in redirection url iam unable to read characters after pound (#) sign. iam just getting redirection url= "http://somepage" while i want it to be "http://somepage#page2" is there is any way i can do this

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  • Parameter pack aware std::is_base_of()

    - by T. Carter
    Is there a possibility to have a static assertion whether a type provided as template argument implements all of the types listed in the parameter pack ie. a parameter pack aware std::is_base_of()? template <typename Type, typename... Requirements> class CommonBase { static_assert(is_base_of<Requirements..., Type>::value, "Invalid."); ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ parameter pack aware version of std::is_base_of() public: template <typename T> T* as() { static_assert(std::is_base_of<Requirements..., T>::value, "Invalid."); return reinterpret_cast<T*>(this); } };

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  • Why does the assignment operator return a value and not a reference?

    - by Nick Lowman
    I saw the example below explained on this site and thought both answers would be 20 and not the 10 that is returned. He wrote that both the comma and assignment returns a value, not a reference. I don't quite understand what that means. I understand it in relation to passing variables into functions or methods i.e primitive types are passed in by value and objects by reference but I'm not sure how it applies in this case. I also understand about context and the value of 'this' (after help from stackoverflow) but I thought in both cases I would still be invoking it as a method, foo.bar() which would mean foo is the context but it seems both result in a function call bar(). Why is that and what does it all mean? var x = 10; var foo = { x: 20, bar: function () {return this.x;} }; (foo.bar = foo.bar)();//returns 10 (foo.bar, foo.bar)();//returns 10

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  • aspectRatio = backingWidth / backingHeight ???

    - by carrots
    What am I doing wrong here, I can't get the result of this division: aspectRatio = backingWidth / backingHeight; I've thought I might try casting to (GLfloat) but that didn't do anything. As I step through the code I see that aspectRatio is 0 after the operation, while backingWidth is clearly 768 and backingHeight is 1029. Here are the types: GLfloat aspectRatio; and // The pixel dimensions of the CAEAGLLayer GLint backingWidth; GLint backingHeight; It must be something basic I'm doing wrong here..

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  • Does this make any sense (Apple-documentation)?

    - by Paperflyer
    Here is a snippet of the official Apple Documentation of AudioBufferList (Core Audio Data Types Reference) AudioBufferList Holds a variable length array of AudioBuffer structures. struct AudioBufferList { UInt32 mNumberBuffers; AudioBuffer mBuffers[1]; }; typedef struct AudioBufferList AudioBufferList; Fields mNumberBuffers The number of AudioBuffer structures in the mBuffers array. mBuffers A variable length array of AudioBuffer structures. If mBuffers is defined as AudioBuffer[1] it is not of variable length and thus mNumberBuffers is implicitly defined as 1. Do I miss something here or is this just nonsense?

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  • Offsite data storage for simple app, or a similar supported persistence mechanism?

    - by jdk
    Question Is there a usable facebook entry point to the Data Storage API that facebook lists on their app admin page for developers, or should I consider an alternate mechanism? What alternative mechanisms exist to simply persist my information offsite (away from my server app) without stuffing it into a cookie that's prone to expire? ... Background The facebook Data Store Admin tool is made available in a facebook App's Settings as seen here: (continue reading below) However when I visit the DataStoreAdmin link nothing works (i.e. clicking the buttons to define the data store types and objects does nothing - I have tried different browsers). The Wiki page for Data Store API hasn't been updated recently and the second last update says the beta Data Store was taken offline. It seems odd the link would be readily available and highly visible at the top of the App configuration area if indeed it's defunct. I was hoping some kind of key/value pair solution to remove the data calls from my own server.

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  • Check constraint on table lookup

    - by bzamfir
    Hi, I have a table, department , with several bit fields to indicate department types One is Warehouse (when true, indicate the department is warehouse) And I have another table, ManagersForWarehouses with following structure: ID autoinc WarehouseID int (foreign key reference DepartmentID from departments) ManagerID int (foreign key reference EmployeeID from employees) StartDate EndDate To set new manager for warehouse, I insert in this table with EndDate null, and I have a trigger that sets EndDate for previous record for that warehouse = StartDate for new manager, so a single manager appears for a warehouse at a certain time. I want to add two check constraints as follows, but not sure how to do this do not allow to insert into ManagersForWarehouses if WarehouseID is not marked as warehouse Do not allow to uncheck Warehouse if there are records in ManagersForWarehouses Thanks

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  • best way to write a-> ..->[a] recursive functions in haskell

    - by Roman A. Taycher
    So I keep having this small problem where I have something like func :: a -> b -> [a] -- or basically any a-> ...-> [a] where ... is any types -> func x y = func' [x] y -- as long as they are used to generate a list of [a] from x func' :: [a] -> b -> [a] func = undefined --situation dependant generates a list from each element and returns it as one long list should I keep it like this? should I use func' hidden by a where? should I only use the [a] - b - [a] version and leave the responsibility of passing [variable] to the callee? I might well need to compose these functions and might want to mess around with the order so I'm leaning towards option 3. What do you think?

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  • What is the best signature for overloaded arithmetic operators in C++?

    - by JohnMcG
    I had assumed that the canonical form for operator+, assuming the existence of an overloaded operator+= member function, was like this: const T operator+(const T& lhs, const T& rhs) { return T(lhs) +=rhs; } But it was pointed out to me that this would also work: const T operator+ (T lhs, const T& rhs) { return lhs+=rhs; } In essence, this form transfers creation of the temporary from the body of the implementation to the function call. It seems a little awkward to have different types for the two parameters, but is there anything wrong with the second form? Is there a reason to prefer one over the other?

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  • How to know if a MySQL UPDATE query fails because information being supplied matches data already in

    - by Mike
    I have a query where the user types a block of text in a textarea field. They are able to save this information in a database. The problem is that if they have not changed the information or if the information matches the data already in the database, I recieve a '0' for affected rows. Usually I display an error that says the query failed when there are no affected rows. How would I 'know' that the 0 affected rows is because the data already exists, so that I can display a more specific error?

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  • Make these 2 sql statements into one with the same functionality

    - by Phil
    I have sql statement one; select linkscat.id, linkscat.category from linkscat, contentlinks, links where contentlinks.linksid = links.id and contentlinks.contentid = @contentid and links.linkscatid = linkscat.id order by linkscat.category and sql statement 2 takes a parameter called @linkscat which is 'id' from the statement above; select * from links where linkscatid= @linkscat I'm running into all types of trouble trying to use many sqldatareaders, nested repeaters etc, but it would be great if all the work could be done in the one statement? Is this possible and if so please can you help by posting the final statement? Thanks greatly, any help much appreciated!

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  • referencing struct fields in c with square brackets and an index instead of . and ->?

    - by lsiebert
    Assuming I have a structure such as: typedef struct { char * string1; char * string2; } TWO_WORDS; such that all the fields are of the same type, and my main has TWO_WORDS tw; can I reference string1 with tw[0] and string2 with two[1]? If so: is this part of the c standard? do i have to cast the struct to an array first? what about fields which are different sizes in memory what about fields which are different types but the same size? can you do pointer arithmetic within a structure? -

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  • Assigning a pointer variable to a const int in C++?

    - by John
    I'm wondering if anyone can explain the following to me: If I write int i = 0; float* pf = i; I get a compile error (gcc 4.2.1): error: invalid conversion from ‘int’ to ‘float*’ Makes sense - they are obviously two completely different types. But if instead I write const int i = 0; float* pf = i; It compiles without error. Why should the 'const' make a difference on the right hand side of the assignment? Isn't part of the idea of the 'const' keyword to be able to enforce type constraints for constant values? Any explanation I have been able to come up with feels kind of bogus. And none of my explanations also explain the fact that const int i = 1; float* pf = i; fails to compile. Can anyone offer an explanation?

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  • Is using a DataSet's column Expression works in background same as manual calculation?

    - by Harikrishna
    I have one datatable which is not bindided and records are coming from the file by parsing it in the datatable dynamically every time. Now there is three columns in the datatable Marks1,Marks2 and FinalMarks. And their types is decimal. Now for making addition of columns Marks1 and Marks2 's records and store it into FinalMarks column,For that what I do is : datatableResult.Columns["FinalMarks"].Expression="Marks1+Marks2"; It's works properly. It can be done in other way also is foreach (DataRow r in datatableResult.Rows) { r["FinalMarks"]=Convert.ToDecimal(r["Marks1"])+Convert.ToDecimal(r["Marks2"]); } Is first approach same as second approach in background means is both approach same or what? EDIT: I want to know that first approach works in background as second approach.

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  • How do I print the method body reflectively?

    - by kunjaan
    Right now I have private static void getMethods(Class<? extends Object> clazz) { Method[] declaredMethods = clazz.getDeclaredMethods(); for (Method aMethod : declaredMethods) { aMethod.setAccessible(true); // Print the declaration System.out.print(Modifier.toString(aMethod.getModifiers()) + " " + aMethod.getReturnType().getSimpleName() + " " + aMethod.getName()); // Get Parameter Types getParameters(aMethod); //Empty Body System.out.println("{}\n"); } } Which prints most information reflectively but creates an empty body. How do I add to the reflective nature of Java to print the method body?

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  • regex no character

    - by iamnotmad
    In this text: warning here there are several types of warnings in this string warning.gif at the end warning end of line warning I want to match every warning except warning.gif. I cannot seem to get it to include the last one that has no character (control or otherwise) after it. using warnings?[^\.] gets what I want except for the last warning (on the last line). I think because there is no character at all after. How can I get it to include that one?

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  • Drupal: tag multiselection.. but not anymore possible adding new tags

    - by Patrick
    hi, I've installed Taxonomy SuperSelect module in my Drupal. Now my customer can not only type the tag for some content types pages but also select multiple tags using checkboxes. I've also ordered the chekboxes alphabetically. However few days ago, I noticed that he can't anymore manually type the tags.. see picture: http://dl.dropbox.com/u/72686/multiSelect.png Can you help me how to solve this issue ? What's the php template to edit this pages ? Unluckily I don't remember if I edited some code, since I found out after a while this bug. thanks

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  • Any way to not break on certain errors in Visual Studio 2010?

    - by Vulgrin
    I'm working on a VS2010 project where I'm using DataAnnotations on my objects to handle validation. However, this is sort of a pain in the butt while trying to do interactive debugging because it keeps pausing VS.Net on validation errors. Obviously, I want to break on some errors, but not these particular types. Am I out of luck and I just need to turn on and off my Break on All Errors setting? Or is there some way to tell VS to just ignore these when they happen? (these are errors generated via Validator.ValidateProperty calls.) Thanks

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  • Core Data: Detecting the type and casting it

    - by Tim Sullivan
    I have set up a Core Data model that includes an entity, Item with a 1-M relationship with the abstract entity Place, so that an item has many places. There are several entities with the parent set to Place. I want to set up several UI elements depending on the descendent place types. I have a loop that looks something like this: for (Place *place in item.places) { } ... but I'm not sure how to detect what type the place is, and how to cast it to the proper type so that I can access its properties. Thanks for any help!

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  • Stringly typed values table in sql, is there a better way to do this? (we're using MSSQL)

    - by Jason Hernandez
    We have have a table layout with property names in one table, and values in a second table, and items in a third. (Yes, we're re-implementing tables in SQL.) We join all three to get a value of a property for a specific item. Unfortunately the values can have multiple data types double, varchar, bit, etc. Currently the consensus is to stringly type all the values and store the type name in the column next to the value. tblValues DataTypeName nvarchar Is there a better, cleaner way to do this?

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  • How do I get a Type[] with arguments from a MethodCallExpression?

    - by Tomas Lycken
    I'm reflecting over a class (in a unit test of said class) to make sure its members have all the required attributes. To do so, I've constructed a couple of helpers, that take an Expression as an argument. I do some checks for it, and take slightly different actions depending on what type of Expression it is, but it's basically the same. Now, my problem is that I have several methods with the same name (but different signatures), and the following code throws an AmbiguousMatchException: // TOnType is a type argument for the type where the method is declared // mce is the MethodCallExpression var m = typeof(TOnType).GetMethod(mce.Method.Name); Now, if I could add an array of Type[] with the types of the arguments to this method as a second parameter to .GetMethod(), the problem would be solved. But how do I find this Type[] array that I need? I have cast the Expression<Func<...>> to an Expression, and then to a MethodCallExpression, and in this method the contents of <...> is not known.

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