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  • Passing derived objects in a constructure

    - by Clarence Klopfstein
    This is a bit of a convoluted question, hopefully I can make it clear. I am finding that this may not be possible, but am trying to see if anybody has a solution. I have four classes, two are core classes and two are those core classes extended: extUser Extends coreUser extSecurity Extends coreSecurity In the constructor for coreUser you have this: public coreUser(string id, ref coreSecurity cs) When trying to extend coreUser you would have this: public extUser(string id ref extSecurity es) : base(id, ref es) This fails because es is of type, extSecurity and the base class expects a type of coreSecurity. I've not found anyway to cast this to allow for me to override this base class in C#. In VB it works just fine. Ideas?

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  • Any way to make a generic List where I can add a type AND a subtype?

    - by user383178
    I understand why I cannot do the following: private class Parent { }; private class Child extends Parent { }; private class GrandChild extends Child { }; public void wontCompile(List<? extends Parent> genericList, Child itemToAdd) { genericList.add(itemToAdd); } My question is there ANY practical way to have a typesafe List where you can call add(E) where E is known to be only a Parent or a Child? I vaguely remember some use of the "|" operator as used for wildcard bounds, but I cannot find it in the spec... Thanks!

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  • How to retrieve all keys (or values) from a std::map?

    - by Owen
    This is one of the possible ways I come out: struct RetrieveKey { template <typename T> typename T::first_type operator()(T keyValuePair) const { return keyValuePair.first; } }; map<int, int> m; vector<int> keys; // Retrieve all keys transform(m.begin(), m.end(), back_inserter(keys), RetrieveKey()); // Dump all keys copy(keys.begin(), keys.end(), ostream_iterator<int>(cout, "\n")); Of course, we can also retrieve all values from the map by defining another functor RetrieveValues. Is there any other way to achieve this easily? (I'm always wondering why std::map does not include a member function for us to do so.)

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  • How do I iterate over a tuple

    - by Caligo
    How can I iterate over a tuple starting from, say, index 1 to 2? The following doesn't work. using boost::fusion::cons; typedef cons<A, cons<B, cons<C, cons<D> > > > MyTuple; MyTuple tuple_; template <class T> struct DoSomething{ DoSomething(T& t) : t_(&t){ } template <class U> void operator()(U u){ boost::fusion::at<mpl::int_<u> >(*t_); } T* t_; }; boost::mpl::for_each< boost::mpl::range_c<int, 1, 3> >( DoSomething<MyTuple>(tuple_) );

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  • How should I get Xcode to link an iOS project that uses a C++ static library

    - by user1681572
    Using Xcode, I've written a Cocoa Touch static library, mainly in C++. It exposes a C interface for the benefit of Objective-C client code. I have a client iOS app that uses it, and everything works and runs as expected, except that I found I needed to include a minimal .cpp file in the client project to get the link to succeed. Otherwise I get C++-related unresolved symbols, e.g. operator new(unsigned long). The above hack is easy and effective, and so I guess I'm not breaking any laws, but is there a proper way to eliminate my linker errors?

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  • Unusual conversion error (string to integer) asp.net

    - by Phil
    I have my repeater item template: <ItemTemplate> <tr><td><%#Container.DataItem("Category")%></td></tr> </ItemTemplate> Hooked up to: s = "SQL that works ok on server" x = New SqlCommand(s, c) x.Parameters.Add("@contentid", SqlDbType.Int) x.Parameters("@contentid").Value = contentid c.Open() r = x.ExecuteReader If r.HasRows Then Linksrepeater.DataSource = r Linksrepeater.DataBind() End If c.Close() r.Close() When I run the code I get: Invalid Cast Exception was not handled by user code (Conversion from string "category" to type 'Integer' is not valid.) I'm not sure how / why it is trying to convert "Category" to integer as in the db it is a string. Can you please tell me how to avoid this error? thanks.

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  • How to insert into std::map.

    - by Knowing me knowing you
    In code below: map<string,vector<int>> create(ifstream& in, const vector<string>& vec) { /*holds string and line numbers into which each string appears*/ typedef map<string,vector<int>> myMap; typedef vector<string>::const_iterator const_iter; myMap result; string tmp; unsigned int lineCounter = 0; while(std::getline(in,tmp)) { const_iter beg = vec.begin(); const_iter end = vec.end(); while (beg < end) { if ( tmp.find(*beg) != string::npos) { result[*beg].push_back(lineCounter);//THIS IS THE LINE I'M ASKING FOR } ++beg; } ++lineCounter; } return result; } How should I do it (check line commented in code) if I want to use insert method of map instead of using operator[]? Thank you.

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  • How do I tell if the ObjectDataSource OnSelected event was called for the selectmethod or selectcou

    - by itchi
    I have an object datasource that looks like this: <asp:ObjectDataSource ID="obdsList" runat="server" EnablePaging="True" SelectCountMethod="GetCountByID" SortParameterName="sortExpression" OldValuesParameterFormatString="original_{0}" SelectMethod="GetByID" TypeName="Services.Users" onselected="obdsList_Selected"> <SelectParameters> <asp:QueryStringParameter Name="ID" QueryStringField="ID" Type="Int32" /> </SelectParameters> </asp:ObjectDataSource> And a onselected event like this: protected void obdsList_Selected(object sender, ObjectDataSourceStatusEventArgs e) { } However, the event method is being called twice.. once with my returned list, and once with the returned Int32 count. If I want to cast e.ReturnValue to the return List how do I differentiate between the count and select methods? I can do a e.ReturnValue.GetType().ToString() but that seems like a hack.

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  • Running for loop depending on size of string vector

    - by xbonez
    I have made a string vector vector actor_; and then added elements in it using push_back. I now want to display all of them, for which I need to run a loop according to the number of elements in the vector. For that, I need to run the following loop: for (int i = 0; i < (int)actor_.size; i++) { } but this returns the following error: error C2440: 'type cast' : cannot convert from 'unsigned int (__thiscall std::vector<_Ty::* )(void) const' to 'int' 1 with 1 [ 1 _Ty=std::string 1 ] 1 There is no context in which this conversion is possible

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  • Is it possible to use inheritance in this situation? (Java)

    - by they changed my name
    I have ClassA and ClassB, with ClassA being the superclass. ClassA uses NodeA, ClassB uses NodeB. First problem: method parameters. ClassB needs NodeB types, but I can't cast from the subclass to the superclass. That means I can't set properties which are unique to NodeB's. Second problem: When I need to add nodes toClassB, I have to instantiate a new NodeB. But, I can't do this in the superclass, so I'd have to rewrite the insertion to use NodeB. Is there a way around it or am I gonna have to rewrite the whole thing?

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  • Print unique ascii characters in eclipse console

    - by Shaded
    Hey guys, Kind of a strange question but... here it goes. Recently my application threw an IOException that the text only had a clubs symbol in it (like the suit in cards) I know this is probably because there was a number in there that was cast to a char and printed to the screen, and I've found where that might have happened. The only problem is, I can't recreate it in eclipse because the eclipse console doesn't want to print those characters for me. All I get are boxes. I figure this is an encoding issue or something but I need eclipse to print out those characters just like the windows console would. Is there a setting I can change to do this?

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  • fill a buffer successively

    - by mkind
    i intend to fill a char-pointer array successively in a for-loop. the content to fill in is a integer so i need to cast. but i didn't get the result i want to.. for (i=0;i<max0;i++){ sprintf(buf, "%d", content[i]); } sprintf replaces the hole buf, but i want to append. for (i=0;i<max0;i++){ buf[i]=(char) contint[i] } but this isn't working too. it seems to me, i get ascii-code of the content[i].

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  • C++: Vector3 type "wall" ?

    - by anon
    Say I have: class Vector3 { float x, y, z; ... bunch of cuntions .. static operator+(const Vector3&, const Vector3); }; Now, suppose I want to have classes: Position, Velocity, that are exactly like Vector3 (basically, I want typedef Vector3 Position; typedef Vector3 Velocity; Except, given: Position position; Vector3 vector3; Velocity velocity; I want to make sure the following can't happen: position + vector3; vector3 + velocity; velocity + position; What is the best way to achieve this?

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  • Strange C++ thread function invocation

    - by Tony
    I have the following: class DThread { virtual void run()=0; _beginthreadex(NULL,0,tfunc,this,0,&m_UIThreadID); // class itself being passed as param to thread function... static unsigned int __stdcall tfunc(void* thisptr) { static_cast<DThread*>(thisptr)->run(); return 0; } //other stuff } The run function is implemented in a derived class. Why is the function that's being called in the thread being called through a cast this pointer? Is this good practise? Can't it just be called directly? The actual function needing to run is in the derived class. My question is

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  • Retrieving a single Guid in CRM 4.0

    - by user1746560
    I'm new to CRM (version 4.0) and i'm trying to return a 'yearid' guide based on a given year (which is also stored in the entity).So far i've got: public static Guid GetYearID(string yearName) { ICrmService service = CrmServiceFactory.GetCrmService(); // Create the query object. QueryExpression query = new QueryExpression("year"); ColumnSet columns = new ColumnSet(); columns.AddColumn("yearid"); query.ColumnSet = columns; FilterExpression filter = new FilterExpression(); filter.FilterOperator = LogicalOperator.And; filter.AddCondition(new ConditionExpression { AttributeName = "yearName", Operator = ConditionOperator.Equal, Values = new object[] { yearName} }); query.Criteria = filter; } But my questions are: A) What code do in addition to this to actually store the Guid? B) Is using a QueryExpression the most efficient way to do this?

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  • Using Linq to filter parents by their children

    - by Nick L
    Having some problems with my Silverlight app (with RIA services) filtering my results. The idea is on the client I set up the EntityQuery and its filters and call load. However this isn't working for me. Heres my code. public void FireQuery(string filterValue) { EntityQuery<Parent> query = m_ParentDomainContext.GetParentQuery(); query = query.Where(p => p.Children.Any(c => c.Name.Contains(filterValue))); m_ParentDomainContext.Load(query, Query_Completed, null); } Compiles just fine, however, runtime I get "Query operator 'Any' is not supported." Exception. Does anyone know of a good way to filter like this? Again, I'm looking for a way to set this up on the client.

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  • C pointer question, dereferencing crash

    - by skynorth
    Why do this work? int *var; while(scanf("%d", &var) && *var != 0) printf("%d \n", var); While this does not? int *var; while(scanf("%d", &var) && var != 0) printf("%d \n", var); Doesn't * (dereference operator) give you the value pointed by the pointer? So why does *var != 0 crash the program, while var != 0 does not?

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  • Determine an object's class returned by a factory method (Error: function does not take 1 arguments

    - by tzippy
    I have a factorymethod that either returns an object of baseclass or one that is of derivedclass (a derived class of baseclass). The derived class has a method virtual void foo(int x) that takes one argument. baseclass however has virtual void foo() without an argument. In my code, a factory method returns a pointer of type bar that definetly points to an object of class derivedclass. However since this is only known at runtime I get a compiler error saying that foo() does not take an argument. Can I cast this pointer to a pointer of type derivedclass? std::auto_ptr<baseclass> bar = classfactory::CreateBar(); //returns object of class derivedclass bar->foo(5); class baseclass { public: virtual void foo(); } class derivedclass : public baseclass { public: virtual void foo(int x); }

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  • What does it mean when a Perl method returns a "hashref"?

    - by Uri
    I'm trying to decrypt a Perl code which I'm not familiar with, somehow related to HashRef. I'm using Amazon::S3, but my question is a general Perl question. See the code below: use Amazon::S3; my $s3 = Amazon::S3->new( ... ); my $response = $s3->buckets; Documentation (here) sais, about s3-buckets: Returns undef on error, else HASHREF of results The following line is working for me, but I don't understand why: for $b in ( @ { $response->{buckets} } ) { print "bucket: " . $b->bucket . "\n"; } I'm Puzzled by each operator on the first line. What type exactly are $response, $respone->{bucket}. Looks like the expression within the for is an array, but I don't understand this syntax: @{ ... }?

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  • How do I put logic in a View a scope or method in a Model?

    - by Angela
    I have the following in the view: <% unless contact_email.statuses.empty?%> (<%= contact_email.statuses.find(:last).status%>) <% end %> contact_email is an instance of a specific model. Could I do something like this? class ContactEmail < ActiveRecord::Base attr_accessible :contact_id, :email_id, :status, :subject, :body, :date_created, :date_sent def status unless contact_email.statuses.empty? contact_email.statuses.find(:last).status end end end is there a better way to do this? is there a way to use the || operator for a default if empty? Basically, I would like to be able to do the following in the View: <%= contact_email.status = IF there is a value, then display it, if not, show nothing.

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  • When convert a void pointer to a specific type pointer, which casting symbol is better, static_cast or reinterpret_cast?

    - by BugCreater
    A beginner question with poor English: Here I got a void* param and want to cast(or change) it to a specific type. But I don't know which "casting symbol" to use. Either**static_cast** and reinterpret_cast works. I want to know which one is better? which one does the Standard C++ recommend? typedef struct { int a; }A, *PA; int foo(void* a) // the real type of a is A* { A* pA = static_cast<A*>(a); // or A* pA = reinterpret_cast<A*>(a);? cout<<pA->a<<endl; return 0; } Here I use A* pA = static_cast(a); or A* pA = reinterpret_cast(a); is more proper?

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  • How can I pass a type as a parameter in scala?

    - by rsan
    I'm having a really hard time trying to figure out how can I store or pass a type in scala. What I want to achive is something like this: abstract class Foo( val theType : type ) object Foo{ case object Foo1 extends Foo(String) case object Foo2 extends Foo(Long) } So at some point I can do this: theFoo match{ case String => "Is a string" case Long => "Is a long" } and when obtaining the object being able to cast it: theFoo.asInstanceOf[Foo1.theType] Is this possible? If is possible, is a good aproach? What I'm trying to achieve ultimately is writing a pseudo schema for byte stream treatment. E.g if I have an schema Array(Foo1,Foo1,Foo2,Foo3,Foo1) I could parse Arrays of bytes that complain with that schema, if at some point I have a different stream of bytes I could just write a new schema Array(Foo3, Foo4, Foo5) without having to reimplement parsing logic. Regards,

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  • fastest method for minimum of two numbers

    - by user85030
    I was going through mit's opencourseware related to performance engineering. The quickest method (requiring least number of clock cycles) for finding the minimum of two numbers(say x and y) is stated as: min= y^((x^y) & -(x<y)) The output of the expression x < y can be 0 or 1 (assuming C is being used) which then changes to -0 or -1. I understand that xor can be used to swap two numbers. Questions: 1. How is -0 different from 0 and -1 in terms of binary? 2. How is that result used with the and operator to get the minimum? Thanks in advance.

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  • Drupal Views: Render Null Result for Relationship as 0

    - by Kyle S
    I have a View configured in Drupal to return nodes, sorting them by their average vote in descending order. For the purpose of the View, the value of the average votes is a Relationship. I noticed that nodes with no votes are displayed after nodes with a negative average. Nodes with no votes should have an average of 0, but I believe the MySQL JOIN is causing NULL values to be returned (as there are no matching rows in the joined table, since a row is created after the first vote is cast for that item). I discovered that with MySQL it is possible to output all values that are NULL in a column as another value with IFNULL(column_name,'other value'). I feel like I would need to modify the Views module in order to obtain this functionality, but I'm hoping that there is some sort of option that returns NULL values in a relation (a relation doesn't exist for the item) as 0 instead of NULL, so that I can properly sort the nodes. The modules I am using include Views, Voting API, Vote Up/Down, and CTools. Thanks.

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  • Extract data from uint8 to double

    - by HADJ AMOR HASSEN
    I have a C function receiving a uint8 pointer with another parameter which is its size (number of bytes). I want to extract double data from this buffer. Here is my code: Write(uint8* data, uint8 size) /* data and size are given by a callback to my function)*/ { double d; for (i = 0; i < size; i++) { d = ((double*)&data)[i]; printf(" d = %d\n"); } } The problem is that I am not receiving what I am sending within an external hardware. I guess that my cast is wrong. I tried other methods but without any good result. I am still not able to get what I send.

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