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  • How to use a object whose copy constructor and copy assignment is private?

    - by coanor
    In reading TCPL, I got a problem, as the title refered, and then 'private' class is: class Unique_handle { private: Unique_handle& operator=(const Unique_handle &rhs); Unique_handle(const Unique_handle &rhs); public: //... }; the using code is: struct Y { //... Unique_handle obj; }; and I want to execute such operations: int main() { Y y1; Y y2 = y1; } although, these code are come from TCPL, but I still can not got the solution... Can anybody help me, appreciate.

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  • Lazy evaluation with ostream C++ operators

    - by SavinG
    I am looking for a portable way to implement lazy evaluation in C++ for logging class. Let's say that I have a simple logging function like void syslog(int priority, const char *format, ...); then in syslog() function we can do: if (priority < current_priority) return; so we never actually call the formatting function (sprintf). On the other hand, if we use logging stream like log << LOG_NOTICE << "test " << 123; all the formating is always executed, which may take a lot of time. Is there any possibility to actually use all the goodies of ostream (like custom << operator for classes, type safety, elegant syntax...) in a way that the formating is executed AFTER the logging level is checked ?

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  • Pointer to a C++ class member function as a global function's parameter?

    - by marcin1400
    I have got a problem with calling a global function, which takes a pointer to a function as a parameter. Here is the declaration of the global function: int lmdif ( minpack_func_mn fcn, void *p, int m, int n, double *x, double *fvec, double ftol) The "minpack_func_mn" symbol is a typedef for a pointer to a function, defined as: typedef int (*minpack_func_mn)(void *p, int m, int n, const double *x, double *fvec, int iflag ); I want to call the "lmdif" function with a pointer to a function which is a member of a class I created, and here is the declaration of this class function: int LT_Calibrator::fcn(void *p, int m, int n, const double *x, double *fvec,int iflag) I am calling a global function like this: info=lmdif(&LT_Calibrator::fcn, 0, m, n, x, fvec, ftol) Unfortunately, I get a compiler error, which says: "error C2664: 'lmdif' : cannot convert parameter 1 from 'int (__thiscall LT_Calibrator::* )(void *,int,int,const double *,double *,int)' to 'minpack_func_mn' 1 There is no context in which this conversion is possible" Is there any way to solve that problem?

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  • SQL Server 2005 stored procedure error

    - by user1670625
    I have created a stored procedure of insert command for employee details in SQL Server 2005 in which one of the parameters is an image for which I have used varbinary as the datatype in the table.. But when I am adding that parameter in the stored procedure I am getting the following error- Implicit conversion from data type varchar to varbinary is not allowed. Use the CONVERT function to run this query. Stored procedure: ( @Employee_ID nvarchar(10)='', @Password nvarchar(10)='', @Security_Question nvarchar(50)='', @Answer nvarchar(50)='', @First_Name nvarchar(20)='', @Middle_Name nvarchar(20)='', @Last_Name nvarchar(20)='', @Employee_Type nvarchar(15)='', @Department nvarchar(15)='', @Photo varbinary(50)='' ) insert into Registration ( Employee_ID, Password, Security_Question, Answer, First_Name, Middle_Name, Last_Name, Employee_Type, Department, Photo ) values ( @Employee_ID, @Password, @Security_Question, @Answer, @First_Name, @Middle_Name, @Last_Name, @Employee_Type, @Department, @Photo ) Table structure: Column Name Data Type Allow Nulls Employee_ID nvarchar(10) Unchecked Password nvarchar(10) Checked Security_Question nvarchar(50) Checked Answer nvarchar(50) Checked First_Name nvarchar(20) Checked Middle_Name nvarchar(20) Checked Last_Name nvarchar(20) Checked Employee_Type nvarchar(15) Checked Department nvarchar(15) Checked Photo varbinary(50) Checked I am not getting what to do..can anyone give me some suggestion or solution? Thanks in advance.

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  • NASM shift operators

    - by Hudson Worden
    How would you go about doing a bit shift in NASM on a register? I read the manual and it only seems to mention these operators , <<. When I try to use them NASM complains about the shift operator working on scalar values. Can you explain what a scalar value is and give an example of how to use and <<. Also, I thought there were a shr or shl operators. If they do exist can you give an example of how to use them? Thank you for your time.

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  • How do I pass (by value) a struct in Objective-C?

    - by Striker
    This one has been driving me mad! I have a struct: typedef struct{ int a; }myStruct; Then I have: myStruct tempStruct; I am trying to pass the struct to a class method whose implementation is: - (void) myFunc:(struct myStruct)oneOfMyStructs{}; I call the method like so: [myClass myFunc:(struct myStruct)tempStruct]; The compiler complains about "Conversion to non-scalar type requested." All I want to do is pass a struct into a class method, but the syntax has me a bit confused. I'm new to Objective-C. Please let me know if you can see where I'm going wrong. I've not been able to pass by reference either, so if you could help me out with that, that would be great! Thanks!

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  • HASHREF in Perl

    - 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 buzzled 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 to store and compare time-zone sensitive times

    - by Chad Moran
    I have a data structure where an entity has times stored as an int (minutes into the day) for fast comparison. The entity also has a Foreign Key reference back to a TimeZone table which contains the .NET CLR ID Name and it's Standard Time/Daylight Time acronyms. Since this information is stored as time-zone insensitive - I was wondering how in LINQ to SQL I could convert this into a UTC DateTime for comparison against other times that will be in UTC. Just to be clear this conversion has to be done server-side so that I can execute filtering on the SQL Server and not the client. I am using .NET 3.5 SP1 and SQL Server 2008.

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  • Multiset of shared_ptrs as a dynamic priority queue: Concept and practice

    - by Sarah
    I was using a vector-based priority queue typedef std::priority_queue< Event, vector< Event >, std::greater< Event > > EventPQ; to manage my Event objects. Now my simulation has to be able to find and delete certain Event objects not at the top of the queue. I'd like to know if my planned work-around can do what I need it to, and if I have the syntax right. I'd also like to know if dramatically better solutions exist. My plan is to make EventPQ a multiset of smart pointers to Event objects: typedef std::multi_set< boost::shared_ptr< Event > > EventPQ; I'm borrowing functions of the Event class from a related post on a multimap priority queue. // Event.h #include <cstdlib> using namespace std; #include <set> #include <boost/shared_ptr.hpp> class Event; typedef std::multi_set< boost::shared_ptr< Event > > EventPQ; class Event { public: Event( double t, int eid, int hid ); ~Event(); void add( EventPQ& q ); void remove(); bool operator < ( const Event & rhs ) const { return ( time < rhs.time ); } bool operator > ( const Event & rhs ) const { return ( time > rhs.time ); } double time; int eventID; int hostID; EventPQ* mq; EventPQ::iterator mIt; }; // Event.cpp Event::Event( double t, int eid, int hid ) { time = t; eventID = eid; hostID = hid; } Event::~Event() {} void Event::add( EventPQ& q ) { mq = &q; mIt = q.insert( boost::shared_ptr<Event>(this) ); } void Event::remove() { mq.erase( mIt ); mq = 0; mIt = EventPQ::iterator(); } I was hoping that by making EventPQ a container of pointers, I could avoid wasting time copying Events into the container and avoid accidentally editing the wrong copy. Would it be dramatically easier to store the Events themselves in EventPQ instead? Does it make more sense to remove the time keys from Event objects and use them instead as keys in a multimap? Assuming the current implementation seems okay, my questions are: Do I need to specify how to sort on the pointers, rather than the objects, or does the multiset automatically know to sort on the objects pointed to? If I have a shared_ptr ptr1 to an Event that also has a pointer in the EventPQ container, how do I find and delete the corresponding pointer in EventPQ? Is it enough to .find( ptr1 ), or do I instead have to find by the key (time)? Is the Event::remove() sufficient for removing the pointer in the EventPQ container? There's a small chance multiple events could be created with the same time (obviously implied in the use of multiset). If the find() works on event times, to avoid accidentally deleting the wrong event, I was planning to throw in a further check on eventID and hostID. Does this seem reasonable? (Dumb syntax question) In Event.h, is the declaration of dummy class Event;, then the EventPQ typedef, and then the real class Event declaration appropriate? I'm obviously an inexperienced programmer with very spotty background--this isn't for homework. Would love suggestions and explanations. Please let me know if any part of this is confusing. Thanks.

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  • CUDA & VS2010 problem

    - by Kristian D'Amato
    I have scoured the internets looking for an answer to this one, but couldn't find any. I've installed the CUDA 3.2 SDK (and, just now, CUDA 4.0 RC) and everything seems to work fine after long hours of fooling around with include directories, NSight, and all the rest. Well, except this one thing: it keeps highlighting the <<< >>> operator as a mistake. Only on VS2010--not on VS2008. On VS2010 I also get several warnings of the following sort: C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\xdebug(109): warning C4251: 'std::_String_val<_Ty,_Alloc>::_Alval' : class 'std::_DebugHeapAllocator<_Ty>' needs to have dll-interface to be used by clients of class 'std::_String_val<_Ty,_Alloc>' Anyone know how this can be fixed?

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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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  • Is converting this ArrayList to a Generic List efficient?

    - by Greg
    The code I'm writing receives an ArrayList from unmanaged code, and this ArrayList will always contain one or more objects of type Grid_Heading_Blk. I've considered changing this ArrayList to a generic List, but I'm unsure if the conversion operation will be so expensive as to nullify the benefits of working with the generic list. Currently, I'm just running a foreach (Grid_Heading_Blk in myArrayList) operation to work with the ArrayList contents after passing the ArrayList to the class that will use it. Should I convert the ArrayList to a generic typed list? And if so, what is the most efficient way of doing so?

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  • How to display Preferences in a View

    - by Sybiam
    I'm building some sort of wizard to create user accounts in Sync and Manage account. I use a ViewFlipper my activity has to be an AccountAuthenticatorActivity. That said it also means I can't inherit PreferenceActivity. So I looked up in the code of PreferenceActivity and I believe it should be possible to have a PreferenceView that inherit from ListView. The Activity part of PreferenceActivity isn't really needed as far as I know. Though the PreferenceManager is what really blocks me. private PreferenceManager onCreatePreferenceManager() { PreferenceManager preferenceManager = new PreferenceManager(this, FIRST_REQUEST_CODE); preferenceManager.setOnPreferenceTreeClickListener(this); return preferenceManager; } This function imply that we can instatiate PreferenceManager using the operator new. Apparently, the sdk hide the constructor of the PreferenceManager. I'm kind of confused. Is there a way to inflate my preferences and display them without PreferenceActivity?

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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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  • Forcing a templated object to construct from a pointer

    - by SalamiArmi
    I have a fictional class: template<typename T> class demonstration { public: demonstration(){} ... T *m_data; } At some point in the program's execution, I want to set m_data to a big block of allocated memory and construct an object T there. At the moment, I've been using this code: void construct() { *m_data = T(); } Which I've now realised is probably not the best idea... wont work under certain cirumstances, if T has a private assignment operator for example. Is there a normal/better way to do what I'm attempting here?

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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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  • python dictionary with constant value-type

    - by s.kap
    hi there, I bumped into a case where I need a big (=huge) python dictionary, which turned to be quite memory-consuming. However, since all of the values are of a single type (long) - as well as the keys, I figured I can use python (or numpy, doesn't really matter) array for the values ; and wrap the needed interface (in: x ; out: d[x]) with an object which actually uses these arrays for the keys and values storage. I can use a index-conversion object (input -- index, of 1..n, where n is the different-values counter), and return array[index]. I can elaborate on some techniques of how to implement such an indexing-methods with reasonable memory requirement, it works and even pretty good. However, I wonder if there is such a data-structure-object already exists (in python, or wrapped to python from C/++), in any package (I checked collections, and some Google searches). Any comment will be welcome, thanks.

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  • C++ Segmentation 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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  • Dynamic order by without using dynamic sql ?

    - by Rohit
    I have the following stored procedure which can be sorted ascending and descending on TemplateName,CreatedOn and UploadedBy. The following SP when runs doesnot sort records.if i replace 2,3,4 by columnname, i got an error message "Conversion failed when converting the nvarchar value 'Test Template' to data type int.".Please suggest how to achieve sorting. CREATE PROCEDURE [dbo].[usp_SEL_GetRenderingTemplate] ( @facilityID INT, @sortOrder VARCHAR(5), @sortExpression VARCHAR(100), @errorCode INT OUTPUT ) AS BEGIN SET NOCOUNT ON ; BEGIN TRY SET @sortOrder = CASE @sortOrder WHEN 'Ascending' THEN 'ASC' WHEN 'Descending' THEN 'DESC' ELSE 'ASC' END SELECT TemplateID, TemplateName, CreatedOn, ( [user].LastName + ' ' + [user].FirstName ) AS UploadedBy FROM Templates INNER JOIN [user] ON [user].UserID = Templates.CreatedBy WHERE facilityid = @facilityID ORDER BY CASE WHEN @sortExpression = 'TemplateName' AND @sortOrder = 'ASC' THEN 2 WHEN @sortExpression = 'CreatedOn' AND @sortOrder = 'ASC' THEN 3 WHEN @sortExpression = 'UploadedBy' AND @sortOrder = 'ASC' THEN 4 END ASC, CASE WHEN @sortExpression = 'TemplateName' AND @sortOrder = 'DESC' THEN 2 WHEN @sortExpression = 'CreatedOn' AND @sortOrder = 'DESC' THEN 3 WHEN @sortExpression = 'UploadedBy' AND @sortOrder = 'DESC' THEN 4 END DESC SET @errorCode = 0 END TRY BEGIN CATCH SET @errorCode = -1 DECLARE @errorMsg AS VARCHAR(MAX) DECLARE @utcDate AS DATETIME SET @errorMsg = CAST(ERROR_MESSAGE() AS VARCHAR(MAX)) SET @utcDate = CAST(GETUTCDATE() AS DATETIME) EXEC usp_INS_LogException 'usp_SEL_GetFacilityWorkTypeList', @errorMsg, @utcDate END CATCH END

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  • Sql server management studio reporting "The semaphore timeout period has expired."

    - by nis-simonsen
    On our development sql server, executing any query containing more than approximately 700 characters stalls for about 10 seconds and then reports the following error: Msg 121, Level 20, State 0, Line 0 A transport-level error has occurred when receiving results from the server. (provider: TCP Provider, error: 0 - The semaphore timeout period has expired.) for example, this query select * from FooTable where id = ' (.. and then 700 spaces ..) ' fails fails with the timeout error while this one select * from FooTable where id = ' (.. and then 600 spaces ..) ' fails with the expected Msg 8169, Level 16, State 2, Line 1 Conversion failed when converting from a character string to uniqueidentifier. - immediately. Indeed, throwing any query, including random garbage at our dev sql server exhibits this behaviour, while any other sql server I have available acts as expected, so I would think that the query never actually gets to parsing on the server. I'm at a loss here - any hints?

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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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  • Using an IN clause in Vb.net to save something to the database using SQL

    - by Rob
    I have a textbox and a button on a form. I wish to run a query (in Vb.Net) that will produce a query with the IN Values. Below is an example of my code myConnection = New SqlConnection("Data Source=sqldb\;Initial Catalog=Rec;Integrated Security=True") myConnection.Open() myCommand = New SqlCommand("UPDATE dbo.Recordings SET Status = 0 where RecID in ('" & txtRecID.Text & "') ", myConnection) ra = myCommand.ExecuteNonQuery() myConnection.Close() MsgBox("Done!", _ MsgBoxStyle.Information, "Done") When I enter a single value it works but when I enter values with commas it throws an error: "Conversion failed when converting the varchar value '1234,4567' to data type int." Could someone please help me to solve this or if there is an alternative way? Many Thanks

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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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  • 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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  • How to Detect Trusted Connection in Crystal Reports using VB.NET?

    - by Michael
    I have some Crystal Reports connecting to a Sql Server db that I would like to detect whether the connection is trusted or whether I need to supply the log on info (reports are not supplied by me so I can't control the connect method). If I just blindly supply login credentials, it won't connect if it is a trusted connection. The following does not work: oRpt = oCR.OpenReport("C:\MyReport.rpt") if oRpt.Database.Tables(1).ConnectionProperties.Item("Integrated Security") = True then 'trusted connection else 'supply login credentials end if It gives the following error: Operator '=' is not defined for type 'IConnectionProperty' and type 'Boolean'. I cannot find how create a construct in vb.net for IConnectionProperty. I can't find any documents from Crystal that explain it. I am using Crystal Reports XI - Developer

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