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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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• 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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• how to get key value of array with curl (php)

  - by Vierri

  Hello I want to make use of an API but it print alot of info and i don't know how i can get a few key values of the array. <?php $query = "SELECT * FROM kvk WHERE adres='Wit-geellaan 158'"; $host = "http://api.openkvk.nl/php/"; $url = $host ."/". rawurlencode($query); $curl = curl_init(); curl_setopt($curl, CURLOPT_FOLLOWLOCATION, 1); curl_setopt($curl, CURLOPT_URL, $url); curl_setopt($curl, CURLOPT_HEADER, 0); curl_exec($curl); curl_close($curl); ?> Is my php script and it shows array(array("RESULT"=>array("TYPES"=>array("int","bigint","varchar","varchar","varchar","varchar","varchar","int","int","smallint","smallint","int"),"HEADER"=>array("id","kvk","bedrijfsnaam","adres","postcode","plaats","type","kvks","sub","bedrijfsnaam_size","adres_size","verhuisd"),"ROWS"=>array(array("1303095","271242250000","Schoonmaakbedrijf Regio","Wit-geellaan 158","2718CK","Zoetermeer","Hoofdvestiging","27124225","0","23","16","0"))))) Thanks in advance Greetings, Vierri

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• Java: How to get Unicode name of a character (or its type category)?

  - by java.is.for.desktop

  Hello, everyone! The Character class in Java defines methods which check a given char argument for equality with certain Unicode chars or for belonging to some type category. These chars and type categories are named. As stated in given javadoc, examples for named chars are HORIZONTAL TABULATION, FORM FEED, ...; example for named type categories are SPACE_SEPARATOR, PARAGRAPH_SEPARATOR, ... However, being byte or int values instead of enums, the name of these types are "hidden" at runtime. So, is there a possibility to get characters' and/or type categories' names at runtime?

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• Qt almost same main menu entries

  - by user1671710

  I'm using c++ Qt library and I want to do something which would do : connect(actionB11, SIGNAL(triggered()), this, SLOT(SetSomething(1, 1))); connect(actionB12, SIGNAL(triggered()), this, SLOT(SetSomething(1, 2))); connect(actionB21, SIGNAL(triggered()), this, SLOT(SetSomething(2, 1))); connect(actionB22, SIGNAL(triggered()), this, SLOT(SetSomething(2, 2))); The code above doesnt work because SIGNAL function has to have same number and argument types as SLOT function. Does exist a way how to do it? I dont want to have about 20 function as SetSomething11, SetSomething12 calling SetSomething(1, 1) etc.

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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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• 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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• 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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• How can I duplicate, or copy a Core Data Managed Object?

  - by 106480833665852483906

  I have a managed object ("A") that contains various attributes and types of relationships, and its relationships also have their own attributes & relationships. What I would like to do is to "copy" or "duplicate" the entire object graph rooted at object "A", and thus creating a new object "B" that is very similar to "A". To be more specific, none of the relationships contained by "B" (or its children) should point to objects related to "A". There should be an entirely new object graph with similar relationships intact, and all objects having the same attributes, but of course different id's. There is the obvious manual way to do this, but I was hoping to learn of a simpler means of doing so which was not totally apparent from the Core Data documentation. TIA!

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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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• Consolidating separate Loan, Purchase & Sales tables into one transaction table.

  - by Frank Computer

  INFORMIX-SE with ISQL 7.3: I have separate tables for Loan, Purchase & Sales transactions. Each tables rows are joined to their respective customer rows by: customer.id [serial] = loan.foreign_id [integer]; = purchase.foreign_id [integer]; = sale.foreign_id [integer]; I would like to consolidate the three tables into one table called "transaction", where a column "transaction.trx_type" [char(1)] {L=Loan, P=Purchase, S=Sale} identifies the transaction type. Is this a good idea or is it better to keep them in separate tables? Storage space is not a concern, I think it would be easier programming & user=wise to have all types of transactions under one table.

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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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• 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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• Any tools can randomly generate the source code according to a language grammar?

  - by wbsun

  A C program source code can be parsed according to the C grammar(described in CFG) and eventually turned into many ASTs. I am considering if such tool exists: it can do the reverse thing by firstly randomly generating many ASTs, which include tokens that don't have the concrete string values, just the types of the tokens, according to the CFG, then generating the concrete tokens according to the tokens' definitions in the regular expression. I can imagine the first step looks like an iterative non-terminals replacement, which is randomly and can be limited by certain number of iteration times. The second step is just generating randomly strings according to regular expressions. Is there any tool that can do this?

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• ExpressJS: What is the difference between app.local and res.local?

  - by aeyang

  I'm trying to learn Express and in my app I have middleware that passes the session object from the Request object to my Response object so that I can access it in my views: app.use((req, res, next) -> res.locals.session = req.session next() ) But app.locals is available to the view as well right? So is it the same if I do app.locals.session = req.session? Is there a convention for the types of things app.locals and res.locals are used for? I was also confused on what the difference is between res.render() and res.redirect()? When should each be used? Thanks for reading. Any help related to Express is appreciated!

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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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• 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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• 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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• When [script] file download fails, how can I tell why?

  - by Bruce

  My web application sends me diagnostic info from the browser javascript telling me that a [script] tag I've injected has failed to download the associated .js file. I can't reproduce this locally, and there is no particular pattern to which file fails, or what the browser type is. There is a pattern to the geo location of the requests - Mexico and Brazil are always more frequent - so I'm guessing that perhaps the internet in general is just more flaky there, and it is just network issues causing the failures. I'd really like to know for sure, though. Is there any way to determine, from the browser javascript, whether the failure occurred because of an error returned by the server, from a network error, or from a protocol timeout? I don't care if the mechanism is browser-specific, since it seems likely that the same issue is causing the error on all browser types.

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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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• Rails - inheritance hierarchy of classes where a subtype can play two roles

  - by Miquel

  I need to model Owners and Rentees in an application, so you have stuff that is always owned by someone and can be rented for someone else. I first approached this problem with Single Table Inheritance because both types of person will share all attributes, so you would have a model called Person associated to a table people with Owner and Rentee inheriting from Person. The problem is that Single type inheritance discerns subtypes using a field type and therefore a record in the table can represent either an Owner or a Rentee but not both at the same time, while in the real context you can have an Owner which is renting something from another Owner and therefore that person is at the same time an Owner and a Rentee. How would you approach this problem? Would you use separated tables for owners and rentees? Is there any other type of table inheritance in Rails?

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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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• 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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• 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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• 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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