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  • database table design

    - by e.b.white
    I design the tables as below for the system which looks like a package delivering system For example, after user received the package, postman should record in system, and the state(history table) is "delivered",and operator is this postman, the current state(state table) is of course "delivered" history table: +---------------+--------------------------+ | Field | Desc | +---------------+--------------------------+ | id | PRIMARY KEY | +---------------+--------------------------+ | package_id | package_tacking_id | +---------------+--------------------------+ | state | package_state | +---------------+--------------------------+ | operators | operators | +---------------+--------------------------+ | create_time| create_time | +---------------+--------------------------+ state table: +---------------+--------------------------+ | Field | Desc | +---------------+--------------------------+ | id | PRIMARY KEY | +---------------+--------------------------+ | package_id | package_tacking_id | +---------------+--------------------------+ | state | latest_package_state | +---------------+--------------------------+ Above is just the basic information to record, some other information( like invoice, destination,...) should be recored as well. But there are different service types like s1 and s2, for s1 it is not needed to record invoice but s1 need, and maybe s1 need some other information to record (like the tel of end user). After all, at delivering way stations there are additional information to record, and for different service type the information type is different. My question is: 1. For different service type, shall I need to declare different tables(option A) or just one big table which can record all information for all types(option B)? 2. If option A, since the basic information above is MUST, how can prevent from declaring there duplicate fields in different tables?

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  • Why it's can be compiled in GNU/C++, can't compiled in VC++2010 RTM?

    - by volnet
    #include #include #include #include "copy_of_auto_ptr.h" #ifdef _MSC_VER #pragma message("#include ") #include // http://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Pragmas.html#Diagnostic-Pragmas #endif /* case 1-4 is the requirement of the auto_ptr. which form http://ptgmedia.pearsoncmg.com/images/020163371X/autoptrupdate/auto_ptr_update.html */ /* case 1. (1) Direct-initialization, same type, e.g. */ std::auto_ptr source_int() { // return std::auto_ptr(new int(3)); std::auto_ptr tmp(new int(3)); return tmp; } /* case 2. (2) Copy-initialization, same type, e.g. */ void sink_int(std::auto_ptr p) { std::cout source_derived() { // return std::auto_ptr(new Derived()); std::auto_ptr tmp(new Derived()); return tmp; } /* case 4. (4) Copy-initialization, base-from-derived, e.g. */ void sink_base( std::auto_ptr p) { p-go(); } int main(void) { /* // auto_ptr */ // case 1. // auto_ptr std::auto_ptr p_int(source_int()); std::cout p_derived(source_derived()); p_derived-go(); // case 4. // auto_ptr sink_base(source_derived()); return 0; } In Eclipse(GNU C++.exe -v gcc version 3.4.5 (mingw-vista special r3)) it's two compile error: Description Resource Path Location Type initializing argument 1 of void sink_base(std::auto_ptr<Base>)' from result ofstd::auto_ptr<_Tp::operator std::auto_ptr<_Tp1() [with _Tp1 = Base, _Tp = Derived]' auto_ptr_ref_research.cpp auto_ptr_ref_research/auto_ptr_ref_research 190 C/C++ Problem Description Resource Path Location Type no matching function for call to `std::auto_ptr::auto_ptr(std::auto_ptr)' auto_ptr_ref_research.cpp auto_ptr_ref_research/auto_ptr_ref_research 190 C/C++ Problem But it's right in VS2010 RTM. Questions: Which compiler stand for the ISO C++ standard? The content of case 4 is the problem "auto_ptr & auto_ptr_ref want to resolve?"

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  • AJAX Request Erroring

    - by 30secondstosam
    I can not figure out for the life of me why this is erroring - can someone please cast a second pair of eyes over this - it's probably something really stupid, thanks in advance for the help: EDIT Stupidly I was putting the wrong URL in - HOWEVER... Now I have put the correct URL in, the site just hangs and crashes. Any ideas please? HTML: <input id="pc" class="sfc" name="ProdCat[]" type="checkbox" value=""> <input id="psc" class="sfc" name="ProdSubCat[]" type="checkbox" value=""> <input id="bf" class="sfc" name="BrandFil[]" type="checkbox" value=""> JQuery: $('input[type="checkbox"]').change(function(){ var name = $(this).attr("name"); var ProdCatFil = []; var ProdSubCatFil = []; var BrandFil = []; // Loop through the checked checkboxes in the same group // and add their values to an array $('input[type="checkbox"]:checked').each(function(){ switch(name) { case 'ProdCatFil[]': ProdCatFil.push($(this).val()); break; case 'ProdSubCatFil[]': ProdSubCatFil.push($(this).val()); break; case 'BrandFil[]': BrandFil.push($(this).val()); break; } }); $("#loading").ajaxStart(function(){ $(this).show(); $('.content_area').hide(); }); $("#loading").ajaxStop(function(){ $(this).hide(); $('.content_area').show(); }); $.ajax({ type: "GET", url: '../ajax/ajax.php', data: 'ProdCatFil='+ProdCatFil+'&ProdSubCatFil='+ProdSubCatFil+'&BrandFil='+BrandFil, success: function(data) { $('.content_area').html(data); } }).error(function (event, jqXHR, ajaxSettings, thrownError) { $('.content_area').html("<h2>Could not retrieve data</h2>"); //alert('[event:' + event + '], [jqXHR:' + jqXHR + '], [ajaxSettings:' + ajaxSettings + '], [thrownError:' + thrownError + '])'); }); PHP (just to prove it's working): echo '<h1>TEST TEST TEST </h1>'; The errors from JQuery alert box: [event:[object Object]], [jqXHR:error], [ajaxSettings:Not Found], [thrownError:undefined])

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  • C++: inheritance problem

    - by Helltone
    It's quite hard to explain what I'm trying to do, I'll try: Imagine a base class A which contains some variables, and a set of classes deriving from A which all implement some method bool test() that operates on the variables inherited from A. class A { protected: int somevar; // ... }; class B : public A { public: bool test() { return (somevar == 42); } }; class C : public A { public: bool test() { return (somevar > 23); } }; // ... more classes deriving from A Now I have an instance of class A and I have set the value of somevar. int main(int, char* []) { A a; a.somevar = 42; Now, I need some kind of container that allows me to iterate over the elements i of this container, calling i::test() in the context of a... that is: std::vector<...> vec; // push B and C into vec, this is pseudo-code vec.push_back(&B); vec.push_back(&C); bool ret = true; for(i = vec.begin(); i != vec.end(); ++i) { // call B::test(), C::test(), setting *this to a ret &= ( a .* (&(*i)::test) )(); } return ret; } How can I do this? I've tried two methods: forcing a cast from B::* to A::*, adapting a pointer to call a method of a type on an object of a different type (works, but seems to be bad); using std::bind + the solution above, ugly hack; changing the signature of bool test() so that it takes an argument of type const A& instead of inheriting from A, I don't really like this solution because somevar must be public.

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  • Isn't an Iterator in c++ a kind of a pointer?

    - by Bilthon
    Ok this time I decided to make a list using the STL. I need to create a dedicated TCP socket for each client. So everytime I've got a connection, I instantiate a socket and add a pointer to it on a list. list<MyTcp*> SocketList; //This is the list of pointers to sockets list<MyTcp*>::iterator it; //An iterator to the list of pointers to TCP sockets. Putting a new pointer to a socket was easy, but now every time the connection ends I should disconnect the socket and delete the pointer so I don't get a huge memory leak, right? well.. I thought I was doing ok by setting this: it=SocketList.begin(); while( it != SocketList.end() ){ if((*it)->getClientId() == id){ pSocket = it; // <-------------- compiler complains at this line SocketList.remove(pSocket); pSocket->Disconnect(); delete pSocket; break; } } But the compiler is saying this: error: invalid cast from type ‘std::_List_iterator<MyTcp*>’ to type ‘MyTcp*’ Can someone help me here? i thought I was doing things right, isn't an iterator at any given time just pointing to one of the elements of the set? how can I fix it?

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  • Can this line of code really throw an IndexOutOfRange exception?

    - by Jonathan M
    I am getting an IndexOutOfRange exception on the following line of code: var searchLastCriteria = (SearchCriteria)Session.GetSafely(WebConstants.KeyNames.SEARCH_LAST_CRITERIA); I'll explain the above here: SearchCriteria is an Enum with only two values Session is the HttpSessionState GetSafely is an extension method that looks like this: public static object GetSafely(this HttpSessionState source, string key) { try { return source[key]; } catch (Exception exc) { log.Info(exc); return null; } } WebConstants.KeyNames.SEARCH_LAST_CRITERIA is simply a constant I've tried everything to replicate this error, but I cannot reproduce it. I am beginning to think the stack trace is wrong. I thought perhaps the exception was actually coming from the GetSafely call, but it is swallowing the exceptions, so that can't be the case, and even if it was, it should show up in the stack trace. Is there anything in the line of code above that could possible throw an IndexOutOfRange exception? I know the line will throw an NullReferenceException if GetSafely returns null, and it will also throw an InvalidCastException if it returns anything that cannot be cast to SearchCriteria, but an IndexOutOfRange exception? I'm scratching my head here. Here is the stack trace: $LOG--> 2010-06-11 07:01:33,814 [ERROR] SERVERA (14) Web.Global - Index was outside the bounds of the array. System.Web.HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.IndexOutOfRangeException: Index was outside the bounds of the array. at IterateSearchResult(Boolean next) in C:\Projects\Web\UserControls\AccountHeader.ascx.cs:line 242 at nextAccountLink_Click(Object sender, EventArgs e) in C:\Projects\Web\UserControls\AccountHeader.ascx.cs:line 232

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  • How to iterate properly across a const set?

    - by Jared
    I'm working on a program that's supposed to represent a graph. My issue is in my printAdjacencyList function. Basically, I have a Graph ADT that has a member variable "nodes", which is a map of the nodes of that graph. Each Node has a set of Edge* to the edges it is connected to. I'm trying to iterate across each node in the graph and each edge of a node. void MyGraph::printAdjacencyList() { std::map<std::string, MyNode*>::iterator mit; std::set<MyEdge*>::iterator sit; for (mit = nodes.begin(); mit != nodes.end(); mit++ ) { std::cout << mit->first << ": {"; const std::set<MyEdge*> edges = mit->second->getEdges(); for (sit = edges.begin(); sit != edges.end(); sit++) { std::pair<MyNode*, MyNode*> edgeNodes = *sit->getEndpoints(); } } std::cout << " }" << std::endl; } getEdges is declared as: const std::set<MyEdge*>& getEdges() { return edges; }; and get Endpoints is declared as: const std::pair<MyNode*, MyNode*>& getEndpoints() { return nodes; }; The compiler error I'm getting is: MyGraph.cpp:63: error: request for member `getEndpoints' in `*(&sit)->std::_Rb_tree_const_iterator<_Tp>::operator-> [with _Tp = MyEdge*]()', which is of non-class type `MyEdge* const' MyGraph.cpp:63: warning: unused variable 'edgeNodes' I have figured out that this probably means I'm misusing const somewhere, but I can't figure out where for the life of me. Any information would be appreciated. Thanks!

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  • XML digital signature interface

    - by yeekang
    I am trying to call a WebService and it requires me to prepare an XML digital signature interface. I came across this website and it shows how to sign an XML document. My problem now is that I do not create the XML document myself. My code is as follows: string myResult; GenericWS.ServicesService a = new GenericWS.ServicesService(); GenericWS.Service2 b = new GenericWS.Service2(); b.Something = "3"; X509Certificate cert = X509Certificate.CreateFromCertFile("C:\\somepath\\somecert.cer"); a.ClientCertificates.Add(cert); ServicePointManager.ServerCertificateValidationCallback = delegate (object s, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors) { return true; }; myResult= a.WSRequest(b).WSReturnValue.ToString(); Label1.Text = myResult; Basically, the WSRequest() will generate the body of the SOAP message. However, in order to sign the SOAP message, I need to pass in the XML file that needs to be signed. I tried to serialize the object and cast it as XML and pass it into the signature interface but I do not have another method that I can invoke to call the webmethod. Is there any other solution?

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  • How to combine the multiple part linq into one query?

    - by user2943399
    Operator should be ‘AND’ and not a ‘OR’. I am trying to refactor the following code and i understood the following way of writing linq query may not be the correct way. Can somone advice me how to combine the following into one query. AllCompany.Where(itm => itm != null).Distinct().ToList(); if (AllCompany.Count > 0) { //COMPANY NAME if (isfldCompanyName) { AllCompany = AllCompany.Where(company => company["Company Name"].StartsWith(fldCompanyName)).ToList(); } //SECTOR if (isfldSector) { AllCompany = AllCompany.Where(company => fldSector.Intersect(company["Sectors"].Split('|')).Any()).ToList(); } //LOCATION if (isfldLocation) { AllCompany = AllCompany.Where(company => fldLocation.Intersect(company["Location"].Split('|')).Any()).ToList(); } //CREATED DATE if (isfldcreatedDate) { AllCompany = AllCompany.Where(company => company.Statistics.Created >= createdDate).ToList(); } //LAST UPDATED DATE if (isfldUpdatedDate) { AllCompany = AllCompany.Where(company => company.Statistics.Updated >= updatedDate).ToList(); } //Allow Placements if (isfldEmployerLevel) { fldEmployerLevel = (fldEmployerLevel == "Yes") ? "1" : ""; AllCompany = AllCompany.Where(company => company["Allow Placements"].ToString() == fldEmployerLevel).ToList(); }

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  • How to read pair in freemarker

    - by Lukasz Rys
    Ok i'm having little trouble with reading pair. So I'm creating my pair private Pair<Integer, Integer> count(somethink) { int c1 = 2; int c2 = 4; return new Pair<Integer, Integer>(c1, c2); } And 'sending' it to ftl via java mv.addObject("counted", count(somethink)); I won't write everythink how it sends because I dont think it really matters with my issue. So i'm recieving it in "ftl". Then i was trying to 'read' it <#list counted?keys as key> <a href="#offerOrderTab"><@spring.message "someMsg"/>(${key}/${counted[key]})</a> </#list> After then i'm getting error Expecting a string, date or number here, Expression x is instead a freemarker.ext.beans.SimpleMethodModel As i suppose you dont iterate pairs (or I'm wrong?) i know its pair that contains only one key and one value but still i have to do send it that way and I thought its goin be to similar to iterating through map, in java i would use pair.first() and pair.second() but it doesn't work in ftl (ye i know it shouldnt work). I also tried to cast it to String by using ?string but it didnt work too

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  • MySQL Casting in C#

    - by user798080
    Okay, so I'm attempting to print out the contents of a table in a comma-separated file. using (OdbcCommand com = new OdbcCommand("SELECT * FROM pie_data WHERE Pie_ID = ?", con)) { com.Parameters.AddWithValue("", Request.Form["pie_id"]); com.ExecuteNonQuery(); using (OdbcDataReader reader = com.ExecuteReader()) { string finalstring = ""; while (reader.Read()) { finalstring = reader.GetString(9) + ","; for (int i = 0; i <= 8; i = i + 1) { finalstring = finalstring + reader.GetString(i) + ","; } } } Response.Write(finalstring); noredirect = 1; } My table layout is: CREATE TABLE `rent_data` ( `Pies` INT(10) UNSIGNED NOT NULL, `Name` VARCHAR(85) NOT NULL, `Email` VARCHAR(85) NOT NULL, `Pie_Rent` DATE NOT NULL, `Rent_To` DATE NOT NULL, `Returned_Date` DATE NULL DEFAULT NULL, `Place` VARCHAR(100) NOT NULL, `Purpose` MEDIUMTEXT NOT NULL, `Comments` MEDIUMTEXT NULL, `Pie_ID` SMALLINT(5) UNSIGNED ZEROFILL NOT NULL, INDEX `Pie_ID` (`Equipment_ID`) ) The error I'm getting is this: Exception Details: System.InvalidCastException: Unable to cast object of type 'System.Int64' to type 'System.String'. On the line: finalstring = finalstring + reader.GetString(i) + ",";

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  • Python to C/C++ const char question

    - by tsukemonoki
    I am extending Python with some C++ code. One of the functions I'm using has the following signature: int PyArg_ParseTupleAndKeywords(PyObject *arg, PyObject *kwdict, char *format, char **kwlist, ...); (link: http://docs.python.org/release/1.5.2p2/ext/parseTupleAndKeywords.html) The parameter of interest is kwlist. In the link above, examples on how to use this function are given. In the examples, kwlist looks like: static char *kwlist[] = {"voltage", "state", "action", "type", NULL}; When I compile this using g++, I get the warning: warning: deprecated conversion from string constant to ‘char*’ So, I can change the static char* to a static const char*. Unfortunately, I can't change the Python code. So with this change, I get a different compilation error (can't convert char** to const char**). Based on what I've read here, I can turn on compiler flags to ignore the warning or I can cast each of the constant strings in the definition of kwlist to char *. Currently, I'm doing the latter. What are other solutions? Sorry if this question has been asked before. I'm new.

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  • Storing Number in an integer from sql Database

    - by ar31an
    i am using database with table RESUME and column PageIndex in it which type is number in database but when i want to store this PageIndex value to an integer i get exception error Specified cast is not valid. here is the code string sql; string conString = "Provider=Microsoft.ACE.OLEDB.12.0; Data Source=D:\\Deliverable4.accdb"; protected OleDbConnection rMSConnection; protected OleDbDataAdapter rMSDataAdapter; protected DataSet dataSet; protected DataTable dataTable; protected DataRow dataRow; on Button Click sql = "select PageIndex from RESUME"; rMSConnection = new OleDbConnection(conString); rMSDataAdapter = new OleDbDataAdapter(sql, rMSConnection); dataSet = new DataSet("pInDex"); rMSDataAdapter.Fill(dataSet, "RESUME"); dataTable = dataSet.Tables["RESUME"]; int pIndex = (int)dataTable.Rows[0][0]; rMSConnection.Close(); if (pIndex == 0) { Response.Redirect("Create Resume-1.aspx"); } else if (pIndex == 1) { Response.Redirect("Create Resume-2.aspx"); } else if (pIndex == 2) { Response.Redirect("Create Resume-3.aspx"); } } i am getting error in this line int pIndex = (int)dataTable.Rows[0][0];

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  • LINQ to SQL: NOTing a prebuilt expression

    - by ck
    I'm building a library of functions for one of my core L2S classes, all of which return a bool to allow checking for certain situations. Example: Expression<Func<Account, bool>> IsSomethingX = a => a.AccountSupplementary != null && a.AccountSupplementary.SomethingXFlag != null && a.AccountSupplementary.SomethingXFlag.Value; Now to query where this is not true, I CAN'T do this: var myAccounts= context.Accounts .Where(!IsSomethingX); // does not compile However, using the syntax from the PredicateBuilder class, I've come up with this: public static IQueryable<T> WhereNot<T>(this IQueryable<T> items, Expression<Func<T, bool>> expr1) { var invokedExpr = Expression.Invoke(expr1, expr1.Parameters.Cast<Expression>()); return items.Where(Expression.Lambda<Func<T, bool>> (Expression.Not(invokedExpr), expr1.Parameters)); } var myAccounts= context.Accounts .WhereNot(IsSomethingX); // does compile which actually produces the correct SQL. Does this look like a good solution, and is there anything I need to be aware of that might cause me problems in future?

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  • Nested bind expressions

    - by user328543
    This is a followup question to my previous question. #include <functional> int foo(void) {return 2;} class bar { public: int operator() (void) {return 3;}; int something(int a) {return a;}; }; template <class C> auto func(C&& c) -> decltype(c()) { return c(); } template <class C> int doit(C&& c) { return c();} template <class C> void func_wrapper(C&& c) { func( std::bind(doit<C>, std::forward<C>(c)) ); } int main(int argc, char* argv[]) { // call with a function pointer func(foo); func_wrapper(foo); // error // call with a member function bar b; func(b); func_wrapper(b); // call with a bind expression func(std::bind(&bar::something, b, 42)); func_wrapper(std::bind(&bar::something, b, 42)); // error // call with a lambda expression func( [](void)->int {return 42;} ); func_wrapper( [](void)->int {return 42;} ); return 0; } I'm getting a compile errors deep in the C++ headers: functional:1137: error: invalid initialization of reference of type ‘int (&)()’ from expression of type ‘int (*)()’ functional:1137: error: conversion from ‘int’ to non-scalar type ‘std::_Bind(bar, int)’ requested func_wrapper(foo) is supposed to execute func(doit(foo)). In the real code it packages the function for a thread to execute. func would the function executed by the other thread, doit sits in between to check for unhandled exceptions and to clean up. But the additional bind in func_wrapper messes things up...

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  • Porting Perl to C++ `print "\x{2501}" x 12;`

    - by jippie
    I am porting a program from Perl to C++ as a learning objective. I arrived at a routine that draws a table with commands like the following: Perl: print "\x{2501}" x 12; And it draws 12 times a '?' ("box drawings heavy horizontal"). Now I figured out part of the problem already: Perl: \x{}, \x00 Hexadecimal escape sequence; C++: \unnnn To print a single Unicode character: C++: printf( "\u250f\n" ); But does C++ have a smart equivalent for the 'x' operator or would it come down to a for loop? UPDATE Let me include the full source code I am trying to compile with the proposed solution. The compiler does throw an errors: g++ -Wall -Werror project.cpp -o project project.cpp: In function ‘int main(int, char**)’: project.cpp:38:3: error: ‘string’ is not a member of ‘std’ project.cpp:38:15: error: expected ‘;’ before ‘s’ project.cpp:39:3: error: ‘cout’ is not a member of ‘std’ project.cpp:39:16: error: ‘s’ was not declared in this scope #include <stdlib.h> #include <stdint.h> #include <stdio.h> #include <string.h> int main ( int argc, char *argv[] ) { if ( argc != 2 ) { fprintf( stderr , "usage: %s matrix\n", argv[0] ); exit( 2 ); } else { //std::string s(12, "\u250f" ); std::string s(12, "u" ); std::cout << s; } }

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  • Need help getting parent reference to child view controller

    - by Andy
    I've got the following code in one of my view controllers: - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { switch (indexPath.section) { case 0: // "days" section tapped { DayPicker *dayPicker = [[DayPicker alloc] initWithStyle:UITableViewStylePlain]; dayPicker.rowLabel = self.activeDaysLabel; dayPicker.selectedDays = self.newRule.activeDays; [self.navigationController pushViewController:dayPicker animated:YES]; [dayPicker release]; break; ... Then, in the DayPicker controller, I do some stuff to the dayPicker.rowLabel property. Now, when the dayPicker is dismissed, I want the value in dayPicker.rowLabel to be used as the cell.textLabel.text property in the cell that called the controller in the first place (i.e., the cell label becomes the option that was selected within the DayPicker controller). I thought that by using the assignment operator to set dayPicker.rowLabel = self.activeDaysLabel, the two pointed to the same object in memory, and that upon dismissing the DayPicker, my first view controller, which uses self.activeDaysLabel as the cell.textLabel.text property for the cell in question, would automagically pick up the new value of the object. But no such luck. Have I missed something basic here, or am I going about this the wrong way? I originally passed a reference to the calling view controller to the child view controller, but several here told me that was likely to cause problems, being a circular reference. That setup worked, though; now I'm not sure how to accomplish the same thing "the right way." As usual, thanks in advance for your help.

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  • Which C++ Standard Library wrapper functions do you use?

    - by Neil Butterworth
    This question, asked this morning, made me wonder which features you think are missing from the C++ Standard Library, and how you have gone about filling the gaps with wrapper functions. For example, my own utility library has this function for vector append: template <class T> std::vector<T> & operator += ( std::vector<T> & v1, const std::vector <T> & v2 ) { v1.insert( v1.end(), v2.begin(), v2.end() ); return v1; } and this one for clearing (more or less) any type - particularly useful for things like std::stack: template <class C> void Clear( C & c ) { c = C(); } I have a few more, but I'm interested in which ones you use? Please limit answers to wrapper functions - i.e. no more than a couple of lines of code.

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  • std::bad_cast from parent to child?

    - by polyglot
    For simplicity, class Parent {} class Child1 : Parent {} class Child2 : Parent {} Elsewhere, I created instances of Child1 and Child2 and store it in same vector under Parent: // . . . in .h file, for example vector<Parent> vector_of_parent; // . . . in one particular method Child1 c1(); Child2 c2(); vector_of_parent.push_back(c1); vector_of_parent.push_back(c2); // . . . Then in another method which has access to vector_of_parent, I tried void doSomething(Parent& some_child) { // wrapped in a try block somehow... Child1& c = dynamic_cast<Child1&> some_child; // do something if the cast is successful } void otherMethod() { doSomething(vector_of_parent.at(0)); // vector_of_parent.at(0) is a Child1 } Why is there a std:bad_cast when I call otherMethod()?

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  • Find XmlNode where attribute value is contained in string

    - by bflemi3
    I have an xml file... <?xml version="1.0" encoding="UTF-8"?> <items defaultNode="1"> <default contentPlaceholderName="pageContent" template="" genericContentItemName="" /> <item urlSearchPattern="connections-learning" contentPlaceholderName="pageContent" template="Connections Learning Content Page" genericContentItemName="" /> <item urlSearchPattern="online-high-school" contentPlaceholderName="pageContent" template="" genericContentItemName="" /> </items> I am trying to find the first node where the urlSearchPattern attribute is contained in the string urlSearchPattern. Where I'm having trouble is finding the nodes where the attribute is contained in the string value instead of the string value be contained in the attribute. Here's my attempt so far. This will find the firstOrDefault node where the string value is contained in the attribute (I need the opposite)... string urlSearchPattern = Request.QueryString["aspxerrorpath"]; MissingPageSettingsXmlDocument missingPageSettingsXmlDocument = new MissingPageSettingsXmlDocument(); XmlNode missingPageItem = missingPageSettingsXmlDocument.SelectNodes(ITEM_XML_PATH).Cast<XmlNode>().Where(item => item.Attributes["urlSearchPattern"].ToString().ToLower().Contains(urlSearchPattern)).FirstOrDefault();

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  • When to use pointer to a class and when to just instantiate it as a variable

    - by Enders
    Im sort of confused by it. The best I could find was reading through the cplusplus.com tutorial and all they have to say about pointers to classes. "It is perfectly valid to create pointers that point to classes. We simply have to consider that once declared, a class becomes a valid type, so we can use the class name as the type for the pointer" Which tells me nothing about when to use them over the normal instantiation. I've seen the - operator many times, and looked at some codes but cant really decipher why they did it. Generic examples will be appreciated; but more specifically related to gui programming. Its where I encountered it first. QGridLayout *mainLayout = new QGridLayout; mainLayout->addWidget(nameLabel, 0, 0); mainLayout->addWidget(nameLine, 0, 1); mainLayout->addWidget(addressLabel, 1, 0, Qt::AlignTop); mainLayout->addWidget(addressText, 1, 1); Why not QGridLayout mainLayout mainLayout.addWidget ... (It doesnt compile if I change the sample code to that and try it but you get the point) Thanks in advance

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  • I want a function to return a type of the subclass its invoked from

    - by Jay
    I want to have a function defined in a superclass that returns a value of the type of the subclass that is used to invoke the function. That is, say I have class A with a function plugh. Then I create subclasses B and C that extend A. I want B.plugh to return a B and C.plugh to return a C. Yes, they could return an A, but then the caller would have to either cast it to the right subtype, which is a pain when used a lot, or declare the receiving variable to be of the supertype, which loses type safety. So I was trying to do this with generics, writing something like this: class A<T extends A> { private T foo; public T getFoo() { return foo; } } class B extends A<B> { public void calcFoo() { foo=... whatever ... } } class C extends A<C> { public void calcFoo() { foo=... whatever ... } } This appears to work but it looks pretty ugly. For one thing, I get warnings on "class A". The compiler says that A is generic and I should specify the type. I guess it wants me to say "class A". But what would I put in for x? I think I could get stuck in an infinite loop here. It seems weird to write "class B extends A", but this causes no complaints, so maybe that's just fine. Is this the right way to do it? Is there a better way?

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  • C++ CRTP question

    - by aaa
    following piece of code does not compile, the problem is in T::rank not be inaccessible (I think) or uninitialized in parent template. Can you tell me exactly what the problem is? is passing rank explicitly the only way? or is there a way to query tensor class directly? Thank you #include <boost/utility/enable_if.hpp> template<class T, // size_t N, class enable = void> struct tensor_operator; // template<class T, size_t N> template<class T> struct tensor_operator<T, typename boost::enable_if_c< T::rank == 4>::type > { tensor_operator(T &tensor) : tensor_(tensor) {} T& operator()(int i,int j,int k,int l) { return tensor_.layout.element_at(i, j, k, l); } T &tensor_; }; template<size_t N, typename T = double> // struct tensor : tensor_operator<tensor<N,T>, N> { struct tensor : tensor_operator<tensor<N,T> > { static const size_t rank = N; }; I know the workaround, however am interested in mechanics of template instantiation for self-education

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  • in haskell, why do I need to specify type constraints, why can't the compiler figure them out?

    - by Steve
    Consider the function, add a b = a + b This works: *Main> add 1 2 3 However, if I add a type signature specifying that I want to add things of the same type: add :: a -> a -> a add a b = a + b I get an error: test.hs:3:10: Could not deduce (Num a) from the context () arising from a use of `+' at test.hs:3:10-14 Possible fix: add (Num a) to the context of the type signature for `add' In the expression: a + b In the definition of `add': add a b = a + b So GHC clearly can deduce that I need the Num type constraint, since it just told me: add :: Num a => a -> a -> a add a b = a + b Works. Why does GHC require me to add the type constraint? If I'm doing generic programming, why can't it just work for anything that knows how to use the + operator? In C++ template programming, you can do this easily: #include <string> #include <cstdio> using namespace std; template<typename T> T add(T a, T b) { return a + b; } int main() { printf("%d, %f, %s\n", add(1, 2), add(1.0, 3.4), add(string("foo"), string("bar")).c_str()); return 0; } The compiler figures out the types of the arguments to add and generates a version of the function for that type. There seems to be a fundamental difference in Haskell's approach, can you describe it, and discuss the trade-offs? It seems to me like it would be resolved if GHC simply filled in the type constraint for me, since it obviously decided it was needed. Still, why the type constraint at all? Why not just compile successfully as long as the function is only used in a valid context where the arguments are in Num? Thank you.

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  • can I store an id value in array of float type ?

    - by srikanth rongali
    I used, for(id value in values) to get the value from an NSArray. Now I want to store it in 2 dimensional float array[][]. When I try to assign the values to array it is giving error:incompatible types in assignment. I tried to cast the value but I got error: pointer value used where a floating point value was expected. I need to store the values in an 2 dimensional array . How can I make it ? Thank You. @implementation fromFileRead1 NSString *fileNameString; int numberOfEnemies, numberOfValues; -(id)init { if( (self = [super init]) ) { NSString *path = @"/Users/sridhar/Desktop/Projects/exampleOnFile2/enemyDetals.txt"; NSString *contentsOfFile = [[NSString alloc] initWithContentsOfFile:path]; NSArray *lines = [contentsOfFile componentsSeparatedByString:@"\n"]; numberOfEnemies = [lines count]; NSLog(@"The number of Lines: %d", numberOfEnemies); for (id line in lines) { NSLog(@"Line %@", line ); NSString *string1 = line; NSArray *split1 = [string1 componentsSeparatedByString:@","]; numberOfValues = [split1 count]; NSLog(@"The number of values in Row: %d", numberOfValues); for (id value in split1) { NSLog(@"value %@", value); float value1; value1 = [split1 objectAtIndex:2]); NSLog(@"VAlue of Value1 at index 2: %f", value1 ); } } } return self; } @end In enemyDetal.txt I have 1,3,3 2,3,2.8 10,2,1.6

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