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  • Accessing subclass members from a superclass pointer C++

    - by Dr. Monkey
    I have an array of custom class Student objects. CourseStudent and ResearchStudent both inherit from Student, and all the instances of Student are one or the other of these. I have a function to go through the array, determine the subtype of each Student, then call subtype-specific member functions on them. The problem is, because these functions are not overloaded, they are not found in Student, so the compiler kicks up a fuss. If I have a pointer to Student, is there a way to get a pointer to the subtype of that Student? Would I need to make some sort of fake cast here to get around the compile-time error?

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  • Casting to global variable from LPVOID - C

    - by Jamie Keeling
    I am trying to cast data to a struct from a parameter passed into my method, I need the data to be passed to a global variable as it is needed elsewhere in my application. I have tried the following but I get errors saying that diceResult is an undeclared identifier Here is the code itself: //Structure to hold dice data typedef struct diceData { int dice1; int dice2; }; struct diceResult; DWORD WINAPI UnpackDiceData(LPVOID sentData) { //Unpack data struct diceData unpackedData = *((struct diceData*)sentData); diceResult.dice1 = unpackedData.dice1; diceResult.dice2 = unpackedData.dice2; } I don't understand why it won't recognise it being there when it's clearly global.

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  • Unreachable code detected in case statement

    - by alex
    I have a code: protected override bool ProcessCmdKey(ref Message msg, Keys keyData) { switch (keyData) { case Keys.Alt|Keys.D1: if (this._condition1) { return true; } else { return base.ProcessCmdKey(ref msg, keyData); } break; case Keys.Control |Keys.U: if (this._condition2) { return true; } else { return base.ProcessCmdKey(ref msg, keyData); } break; default: return base.ProcessCmdKey(ref msg, keyData); } return true; It gives me "unreachable code detected" warning on breaks. Is it good practice not to use break operator here ? I don't want to turn off "unreachable code detected" warning. PS: There are many case in my ProcessCmdKey method.

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  • casting between sibling classes, AS3

    - by felix-gasca
    I have two classes, derivedClassA and derivedClassB which both extend parentClass I'm declaring var o:parentClass and then, depending on what's going on, I want to cast o as either being of type derivedClassA or derivedClassB. Essentially, this: var o:parentClass ... if(shouldUseA) o = new derivedClassA(); else o = new derivedClassB(); o.doSomething(); But it's not working, I'm getting all sorts of errors. Isn't this how class inheritance works? I feel like I'm missing something really fundamental, but I can't figure out what. Am I supposed to be using interfaces instead? Is there another way of doing what I want?

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  • On Memory Allocation and C++

    - by Arpan
    And I quote from MSDN http://msdn.microsoft.com/en-us/library/aa366533(VS.85).aspx: The malloc function has the disadvantage of being run-time dependent. The new operator has the disadvantage of being compiler dependent and language dependent. Now the questions folks: a) What do we mean that malloc is run-time dependent? What kind of dynamic memory allocation functions can be independent of run-time? This statement sounds real strange. b) new is language dependent? Of course it should be right? Are HeapAlloc, LocalAlloc etc language independent? c) From a pure performance perspective are the MSVC provided routines preferable? Arpan

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  • Bit conversion operations in PHP

    - by Goro
    Hello, I find myself in need of performing bit-level conversion on variables in PHP. In more detail, I have a bit stream that is read as an integer by hardware, and I need to do some operations on the bits to make it into what its actually supposed to be (a float). I have to do this a few times for different formats, and the functionality I need is Being able to select and move individual bits in a variable Being able to cast statically one type of variable to the other (ie. int to float) I know php natively supports bitwise AND, OR, etc, and shift operations, but I was wondering if: there may already be a library in php that does this sort of thing I would be better off with delegating the calculations to some other language Thanks,

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  • C++ refactor common code with one different statement

    - by user231536
    I have two methods f(vector<int>& x, ....) and g(DBConn& x, ....) where the (....) parameters are all identical. The code inside the two methods are completely identical except for one statement where we do different actions based on the type of x: in f(): we do x.push_back(i) in g(): we do x.DeleteRow(i) What is the simplest way to extract the common code into one method and yet have the two different statements? I am thinking of having a templated functor that overloads operator () (int a) but that seems overkill.

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  • Double Inner Join generates unexpected error

    - by Itamar Marom
    In my database I have three tables: Users: UserID (Auto Numbering), UserName, UserPassword and a few other unimportant fields. PrivateMessages: MessageID (Auto Numbering), SenderID and a few other fields defining the message content. MessageStatus: MessageID, ReceiverID, MessageWasRead (Boolean) What I need is a query to which I input a user's id and I get all the private messages he has received. In addition, I also need to receive each message's sender UserName. For this I wrote the following query: SELECT Users.*, PrivateMessages.*, MessageStatus.* FROM PrivateMessages INNER JOIN Users ON PrivateMessages.SenderID = Users.UserID INNER JOIN MessageStatus ON PrivateMessages.MessageID = MessageStatus.MessageID WHERE MessageStatus.ReceiverID=[@userid]; But for some reason when I try saving it in my Access database, I get the following error (translated to English by me, since my office is in a different language): Syntax error (missing operator) at expression: "PrivateMessages.SenderID = Users.UserID INNER JOIN MessageStatus ON PrivateMessages.MessageID = MessageStatus.MessageI". Any ideas what could cause this? Thanks.

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  • Updating files with a Perforce trigger before submit [migrated]

    - by phantom-99w
    I understand that this question has, in essence, already been asked, but that question did not have an unequivocal answer, so please bear with me. Background: In my company, we use Perforce submission numbers as part of our versioning. Regardless of whether this is a correct method or not, that is how things are. Currently, many developers do separate submissions for code and documentation: first the code and then the documentation to update the client-facing docs with what the new version numbers should be. I would like to streamline this process. My thoughts are as follows: create a Perforce trigger (which runs on the server side) which scans the submitted documentation files (such as .txt) for a unique term (such as #####PERFORCE##CHANGELIST##NUMBER###ROFL###LOL###WHATEVER#####) and then replaces it with the value of what the change list would be when submitted. I already know how to determine this value. What I cannot figure out, is how or where to update the files. I have already determined that using the change-content trigger (whether possible or not), which "fire[s] after changelist creation and file transfer, but prior to committing the submit to the database", is the way to go. At this point the files need to exist somewhere on the server. How do I determine the (temporary?) location of these files from within, say, a Python script so that I can update or sed to replace the placeholder value with the intended value? The online documentation for Perforce which I have found so far have not been very explicit on whether this is possible or how the mechanics of a submission at this stage would work.

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  • Filter objects within two seconds of one another using SQLAlchemy

    - by Arrieta
    Hello: I have two tables with a column 'date'. One holds (name, date) and the other holds (date, p1, p2). Given a name, I want to use the date in table 1 to query p1 and p2 from table two; the match should happen if date in table one is within two seconds of date in table two. How can you accomplish this using SQLAlchemy? I've tried (unsuccessfully) to use the between operator and with a clause like: td = datetime.timedelta(seconds=2) q = session.query(table1, table2).filter(table1.name=='my_name').\ filter(between(table1.date, table2.date - td, table2.date + td)) Any thoughts?

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  • Possible to fire asp.net validation from jQuery?

    - by Abe Miessler
    I have a form with several text boxes on it. I only want to accept floats, but it is likely that users will enter a dollar sign. I'm using the following code to remove dollar signs and validate the content: jQuery: $("#<%= tb.ClientID %>").change(function() { var ctrl = $("#<%= tb.ClientID %>"); ctrl.val(ctrl.val().replace('$','')) }); asp.net validation: <asp:CompareValidator ID="CompareValidator4" runat="server" Type="Double" ControlToValidate="tb" Operator="DataTypeCheck" ValidationGroup="vld_Page" ErrorMessage="Some error" /> My problem is that when someone enters a dollar sign in the TextBox "tb" and changes focus the validation happens first and THEN the jQuery removes the dollar sign. Is it possible to have the jQuery run first or to force the validation to run again after the jQuery executes?

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  • sql boolean truth test: zero OR null

    - by AK
    Is there way to test for both 0 and NULL with one equality operator? I realize I could do this: WHERE field = 0 OR field IS NULL But my life would be a hundred times easier if this would work: WHERE field IN (0, NULL) (btw, why doesn't that work?) I've also read about converting NULL to 0 in the SELECT statement (with COALESCE). The framework I'm using would also make this unpleasant. Realize this is oddly specific, but is there any way to test for 0 and NULL with one WHERE predicate?

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  • Boost::asio bug in MSVC10 - Failing BOOST_WORKAROUND in ~buffer_debug_check() in buffer.hpp

    - by shaz
    A straight compilation of example http://www.boost.org/doc/libs/1_43_0/doc/html/boost_asio/tutorial/tutdaytime3/src.html results in a runtime null pointer exception. Stack trace points to the buffer_debug_check destructor which contains this comment: // MSVC's string iterator checking may crash in a std::string::iterator // object's destructor when the iterator points to an already-destroyed // std::string object, unless the iterator is cleared first. The test #if BOOST_WORKAROUND(BOOST_MSVC, = 1400) succeeds in MSVC10 and (but) results in a null pointer exception in c:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\include\xutility line 123 _Iterator_base12& operator=(const _Iterator_base12& _Right) { // assign an iterator if (_Myproxy != _Right._Myproxy) _Adopt(_Right._Myproxy->_Mycont); return (*this); } _Right._Myproxy is NULL

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  • How to test Text Search accuracy and efficiency?

    - by DEN
    I have created a web application. One of the feature is text search which perform the boolean operator ( NOT, AND, OR) as well. However, I have no idea on calculating the search's accuracy and efficiency. For example: 1 . Probe identification system for a measurement instrument 2 . Pulse-based impedance measurement instrument 3 . Millimeter with filtered measurement mode when the user key in will return the result as below input :measurement instrument Result: 1,2 input : measurement OR instrument NOT milimeter Result: 1,2,3 so, i have no idea on what issue and what algorithm to calculate on the accuracy and efficiency of the text search.. anyone have any idea on that?

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  • C++ Segementation fault in binary_function

    - by noryb009
    I'm using Visual Studio 2010 Beta 2 (also tried with NetBeans), and I'm having a segmentation fault in the following code: // One of the @link s20_3_3_comparisons comparison functors@endlink. template <class _Tp> struct less : public binary_function<_Tp, _Tp, bool> { bool operator()(const _Tp& __x, const _Tp& __y) const { return __x < __y; } //this is the problem line }; I don't know what in my program calls it, but I am trying to find out. (I think it's a map) Does anyone know what to do, or has encountered this before?

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  • Why wasn't C# designed with 'const' for variables and methods?

    - by spoulson
    I suspect const was simplified for the C# spec for general language simplicity. Was there a specific reason we can't declare variable references or methods as const like we can with C++? e.g.: const MyObject o = new MyObject(); // Want const cast referenece of MyObject o.SomeMethod(); // Theoretically legal because SomeMethod is const o.ChangeStuff(); // Theoretically illegal because ChangeStuff is not const class MyObject { public int val = 0; public void SomeMethod() const { // Do stuff, but can't mutate due to const declaration. } public void ChangeStuff() { // Code mutates this instance. Can't call with const reference. val++; } }

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  • In Outlook 2007 Rules and Alerts, EXACTLY what does "my name" mean?

    - by Cornan The Iowan
    I can't find any definition of "my name" in the Outlook 2007 Rules and Alerts or on the Internet. In this case our email system presents two email addresses for me to the outside world. I'd like BOTH of these addresses to be recognized as being "me". I thought that perhaps if I understood the definition of "my name" in the rules, I could set up my mailbox(es) appropriately. Of course if "my name" actually means a single email address, then I won't be able to do so, but if it means "any email on my account" or "any account meeting [some criteria]", then I might be successful. I'd like to note a subtlety in the rules definitions. While there is a rule named "where my name is in the To or Cc box", the only rule for explicit addresses is "sent to people or distribution list" (I'm assuming that "sent to" means "in the To:" list rather than "in the To: or cc: lists"). Summing up. My preference: 1) Understanding the precise definition of "my name" so that I can use "where my name is in the To or Cc box" to capture both email addresses from my account. 2) Learning the "sent to people or distribution list" actually includes Cc: entries (I can test this myself of course) 3) Any other solution that will let me define a rule where my secondary email address will be detected in EITHER the To: or Cc: boxes.

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  • Enumerable.Range in and Expression and Entity Framework

    - by eka808
    I'm currently developping an expression method (used in linq to entity queries) who has to give me a daycount for a given period (start date and end date) decrementing this daycount if specials days are in the period. My idea was the following : Generate an enumerable with all the dates (and with Enumerable.Range) Make a .Where on this enumerable to remove the specials dates Like a MyEnumerable.Where(a = a != "20120101") After that, return a MyEnumerable.Count() I come with this code : return (p) => Enumerable .Range(1, 4) .Where(a => a != 20120101) .AsQueryable() .Count() I tried to cast as a list, as a queryable, both (like the example) and no way ! it doesn't work ! I always get this error : LINQ to Entities does not recognize the method 'System.Collections.Generic.IEnumerable`1[System.Int32] Range(Int32, Int32)' method, and this method cannot be translated into a store expression. Have you got an idea about that ? Using an enumerable is of course not mandatory, any working solutions is good ^^ Thank's by advance !

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  • Inheritance and Implicit Type Casting

    - by Josué Molina
    Suppose I have the following three classes: class Animal {}; class Human : public Animal {}; class Dog : public Animal { public: void setOwner(Animal* owner) { this->owner = owner; } private: Animal* owner; }; Why is the following allowed, and what exactly is happening? Dog d; Human h; d.setOwner(&h); // ? At first, I tried to cast it like this d.setOwner(&(Animal)h), but the compiler gave me a warning, and I hit a run-time error. Edit: the warning the compiler gave me was "taking address of temporary". Why is this so?

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  • has_many conditions or proc on foreign key

    - by ere
    I have a has_many association between two models using a date as both the foreign and primary key for each model. It works perfectly one way but not the other. Works has_one :quiz_log, :primary_key => :start_at, :foreign_key => :start_at Doesn't work has_many :event_logs, :primary_key => :start_at, :foreign_key => :start_at The reason being (i think) because the start_at on QuizLog is a date and the start_at on EventLog is a datetime. So it returns nil trying to match the exact datetime on a simple date. How can I cast the foreign_key start_at on the second statement to convert it first from datetime to simply date so it will match the second model?

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  • DependencyProperty Orientation problem

    - by byte
    I am learning WPF and am trying to create my first UserControl. My UserControl consists of StackPanel StackPanel contains a Label and TextBox I am trying to create two Dependency Properties Text for the Label Orientation for the StackPanel - The orientation will affect the position of the Label and TextBox effectively I have successfully created a Text dependency property and bind it to my UserControls . But when I created the Orientation property, I seem to get following error in get property The as operator must be used with a reference type or nullable type ('System.Windows.Controls.Orientation' is a non-nullable value type) public static DependencyProperty OrientationProperty = DependencyProperty.Register("Orientation", typeof(System.Windows.Controls.Orientation), typeof(MyControl), new PropertyMetadata((System.Windows.Controls.Orientation)(Orientation.Horizontal))); public Orientation Orientation { get { return GetValue(OrientationProperty) as System.Windows.Controls.Orientation; } set { SetValue(OrientationProperty, value); } } Appreciate your help.

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  • Wrong command in shell

    - by jask
    I have this command in a shell archive: sh -c $POSTGRESbin'psql -U '$POSTGRESuser' -h localhost -d '$POSTGRESdb' -c "select preview from '$fildCatalog' where preview <>'nodata' and id_registro in (select distinct(id_record) from e3_article_items where id_catalog=2101 and id_article in (select id_article from document_articles where id_document in(select distinct(id_document) from p3_logical_pages where id_logical_page in (select id_logical_page from p3_flatplan_pages where id_edition=1536 and id_logical_page is not null order by cast(pagenumber as numeric)))));"' > $queryFolder$highFile"_"$previewFile; But in <'nodata' appear an error and I don't know how can I resolve it. The error is: ERROR: column "nodata" does not exist LINE 1: select preview from XT_FIJOS where preview <>nodata and id_r... Can anybody help me ? Thanks !! ^

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  • Linq to NHibernate - How to return a parent object with only certain child objects included

    - by vakman
    Given a simplified model like the following: public class Enquiry { public virtual DateTime Created { get; set; } public virtual Sender Sender { get; set; } } public class Sender { public virtual IList<Enquiry> Enquiries { get; set; } } How can you construct a Linq to Nhibernate query such that it gives you back a list of senders and their enquiries where the enquiries meet some criteria. I have tried something like this: return session.Linq<Enquiry>() .Where(enquiry => enquiry.Created < DateTime.Now) .Select(enquiry => enquiry.Sender) In this case I get an InvalidCastException saying you can't cast type Sender to type Enquiry. Any pointers on how I can do this without using HQL?

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  • How do I dynamically define an instance variable?

    - by Moses
    Hi everyone, I have two classes (class1 and class2) that just store data, no methods. I have a third class that has an instance variable that, depending on some user input, will be set to one of the two classes. So, in the third class I declare the variable generically as NSObject *aClass; and during runtime set it to whatever it should be. aClass = [[Class1 alloc] init]; // or aClass = [[Class2 alloc] init]; However, when I try to access fields from aClass NSString *str = aClass.field1; It gives me the error: request for member 'field1' in something not a structure or a union. Field1 is declared in both class1 and class2. When I try to cast aClass aClass = (Class1 *) aClass; it gives the same error. What am I doing wrong, is there a better way to do this?

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  • How often do you implement the big three?

    - by Neil Butterworth
    I was just musing about the number of questions here that either are about the "big three" (copy constructor, assignment operator and destructor) or about problems caused by them not being implemented correctly, when it occurred to me that I could not remember the last time I had implemented them myself. A swift grep on my two most active projects indicate that I implement all three in only one class out of about 150. That's not to say I don't implement/declare one or more of them - obviously base classes need a virtual destructor, and a large number of my classes forbid copying using the private copy ctor & assignment op idiom. But fully implemented, there is this single lonely class, which does some reference counting. So I was wondering am I unusual in this? How often do you implement all three of these functions? Is there any pattern to the classes where you do implement them?

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