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• jQuery + form + textinput > Is it possible to display one value in a textinput and submit another?

  - by Ivan Kruchkoff

  I'm working on an application where dates are passed as yyyy-mm-dd but displayed to the client as mm-dd-yyyy (US based client). I'm using a jQuery datepicker for selecting from/to dates in a report and would like to show the dates to the client as mm-dd-yyyy but when the form is submitted, submit as yyyy-mm-dd. Is it possible to display one value in a textinput textbox and have another submitted without needing to hook into onSubmit? I've come up with the following alternatives: Hide the text input for the from and to fields, create dummy fields and make use of the following jQuery date picker functions: altField and altFormat to display the value to the client in their preferred way and deal only with the submitted values which are set through the alt functions. Have an onSubmit javascript call to change the dates from mm-dd-yyyy to dd-mm-yyyy and also change the value=" to change the date to the client's preferred format. Rewrite the app to handle all dates in mm-dd-yyyy and hope the client never has non-US customers that would like their dates in a specific format. Change all dates to dd-Mon-YYYY e.g. 26-May-2010 as all of our client's customers are guaranteed to be English only.

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• Make function declarations based on function definitions

  - by Clinton Blackmore

  I've written a .cpp file with a number of functions in it, and now need to declare them in the header file. It occurred to me that I could grep the file for the class name, and get the declarations that way, and it would've worked well enough, too, had the complete function declaration before the definition -- return code, name, and parameters (but not function body) -- been on one line. It seems to me that this is something that would be generally useful, and must've been solved a number of times. I am happy to edit the output and not worried about edge cases; anything that gives me results that are right 95% of the time would be great. So, if, for example, my .cpp file had: i2cstatus_t NXTI2CDevice::writeRegisters( uint8_t start_register, // start of the register range uint8_t bytes_to_write, // number of bytes to write uint8_t* buffer = 0) // optional user-supplied buffer { ... } and a number of other similar functions, getting this back: i2cstatus_t NXTI2CDevice::writeRegisters( uint8_t start_register, // start of the register range uint8_t bytes_to_write, // number of bytes to write uint8_t* buffer = 0) for inclusion in the header file, after a little editing, would be fine. Getting this back: i2cstatus_t writeRegisters( uint8_t start_register, uint8_t bytes_to_write, uint8_t* buffer); or this: i2cstatus_t writeRegisters(uint8_t start_register, uint8_t bytes_to_write, uint8_t* buffer); would be even better.

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• Checking if a function has C-linkage at compile-time

  - by scjohnno

  Is there any way to check if a given function is declared with C-linkage (that is, with extern "C") at compile-time? I am developing a plugin system. Each plugin can supply factory functions to the plugin-loading code. However, this has to be done via name (and subsequent use of GetProcAddress or dlsym). This requires that the functions be declared with C-linkage so as to prevent name-mangling. It would be nice to be able to throw a compiler error if the referred-to function is declared with C++-linkage (as opposed to finding out at runtime when a function with that name does not exist). Here's a simplified example of what I mean: extern "C" void my_func() { } void my_other_func() { } // Replace this struct with one that actually works template<typename T> struct is_c_linkage { static const bool value = true; }; template<typename T> void assertCLinkage(T *func) { static_assert(is_c_linkage<T>::value, "Supplied function does not have C-linkage"); } int main() { assertCLinkage(my_func); // Should compile assertCLinkage(my_other_func); // Should NOT compile } Thanks.

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• Who needs singletons?

  - by sexyprout

  Imagine you access your MySQL database via PDO. You got some functions, and in these functions, you need to access the database. The first thing I thought of is global, like: $db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'root', 'pwd'); function some_function() { global $db; $db->query('...'); } But it's considered as a bad practice. So, after a little search, I ended up with the Singleton pattern, which "applies to situations in which there needs to be a single instance of a class." According to the example of the manual, we should do this: class Database { private static $instance, $db; private function __construct(){} static function singleton() { if(!isset(self::$instance)) self::$instance = new __CLASS__; return self:$instance; } function get() { if(!isset(self::$db)) self::$db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'user', 'pwd') return self::$db; } } function some_function() { $db = Database::singleton(); $db->get()->query('...'); } some_function(); But I just can't understand why you need that big class when you can do it merely with: class Database { private static $db; private function __construct(){} static function get() { if(!isset(self::$rand)) self::$db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'user', 'pwd'); return self::$db; } } function some_function() { Database::get()->query('...'); } some_function(); This last one works perfectly and I don't need to worry about $db anymore. But maybe I'm forgetting something. So, who's wrong, who's right?

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• How to cancel a deeply nested process

  - by Mystere Man

  I have a class that is a "manager" sort of class. One of it's functions is to signal that the long running process of the class should shut down. It does this by setting a boolean called "IsStopping" in class. public class Foo { bool isStoping void DoWork() { while (!isStopping) { // do work... } } } Now, DoWork() was a gigantic function, and I decided to refactor it out and as part of the process broke some of it into other classes. The problem is, Some of these classes also have long running functions that need to check if isStopping is true. public class Foo { bool isStoping void DoWork() { while (!isStopping) { MoreWork mw = new MoreWork() mw.DoMoreWork() // possibly long running // do work... } } } What are my options here? I have considered passing isStopping by reference, which I don't really like because it requires there to be an outside object. I would prefer to make the additional classes as stand alone and dependancy free as possible. I have also considered making isStopping a property, and then then having it call an event that the inner classes could be subscribed to, but this seems overly complex. Another option was to create a "Process Cancelation Token" class, similar to what .net 4 Tasks use, then that token be passed to those classes. How have you handled this situation? EDIT: Also consider that MoreWork might have a EvenMoreWork object that it instantiates and calls a potentially long running method on... and so on. I guess what i'm looking for is a way to be able to signal an arbitrary number of objects down a call tree to tell them to stop what they're doing and clean up and return.

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• Freetype2 (error-)return value documentation

  - by Awaki

  In short, I'm looking for documentation that would limit the error situations to check for after a Freetype library function failed, much like the OpenGL and Win32 APIs document the error codes generated by their respective functions. I can't seem to find such documentation though, so I was wondering how to best handle translation of Freetype errors to typed exceptions. Background: I am currently in the process of implementing font-rendering capability (using Freetype) for my GUI framework, which makes strong use of typed exceptions to indicate error situations. However, the Freetype docs seem to completely omit what errors can be expected from what functions. That, if such documentation does indeed not exist, would basically leave me with two options: either guessing which errors make sense for a certain Freetype function (obviously prone to mistakes on my part), or considering every error code for translation into appropriate exceptions (less verbose since I would have to write the translation only once). Performance isn't really critical in the code that calls the Freetype library, so even the latter option would probably be acceptable, but surely there must be some kind of documentation on which library calls may return what Freetype error? Is there any such documentation which I just somehow managed to not find? Should I go the route of generically expecting every error code for translation? Or are there other ways to approach this problem? By the way, I wanted to avoid introducing some kind of generic FreetypeException (containing a description of the Freetype error) since I intended to completely hide what libraries I'm using (not from a legal point-of-view, mind you), but I guess I can be convinced to do this anyway if the consensus is that it would be the best option. I don't think it matters for this question, but I'm writing in C++.

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• best database design for city zip & state tables

  - by ryan a

  My application will need to reference addresses. Street info will be stored with my main objects but the rest needs to be stored seperately to reduce redundancy. How should I store/retrieve ZIPs, cities and states? Here are some of my ideas. single table solution (cant do relationships) [locations] locationID locationParent (FK for locationID - 0 for state entries) locationName (city, state) locationZIP two tables (with relationships, FK constraints, ref integrity) [state] stateID stateName [city] cityID stateID (FK for state.stateID) cityName zipCode three tables [state] stateID stateName [city] cityID stateID (FK for state.stateID) cityName [zip] zipID cityID (FK for city.cityID) zipName Then I read into ZIP codes amd how they are assigned. They aren't specifically related to cities. Some cities have more than one ZIP (ok will still work) but some ZIPs are in more than one city (oh snap) and some other ZIPs (very few) are in more than one state! Also some ZIPs are not even in the same state as the address they belong to at all. Seems ZIPs are made for carrier route identification and some remote places are best served by post offices in neighboring cities or states. Does anybody know of a good (not perfect) solution that takes this into consideration to minimize discrepencies as the database grows?

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• ctypes DLL with optional dependencies

  - by pisswillis

  Disclaimer: I'm new to windows programming so some of my assumptions may be wrong. Please correct me if so. I am developing a python wrapper for a C API using ctypes. The API ships with both 64 and 32 DLLs/LIBs. I can succesfully load the DLL using ctypes.WinDLL('TheLibName') and call functions etc etc. However some functions were not doing what they should. Upon further investigation it appears that the 32bit DLL is being used, which is what is causing the unexpected behaviour. I have tried using ctypes.WinDLL('TheLibName64') but the module is not found. I have tried registering the DLL with regsrv32, but it reports there is no entry point (it also reports no entry point when I try and register TheLibName, which is found by WinDLL(). The DLL came with a sample project in Visual Studio (I have 0 experience with VS so again please correct me here) which builds both 32 and 64 bit versions of the sample project. In the .vcsproj file the configurations for the 64 bit version include: AdditionalDependencies="TheLibName64.lib" in the VCLinkerTool section. In windows/system32 there are both TheLibName.dll/.lib, and TheLibName64.dll/.lib. So it seems to me that my problem is now to make the python ctypes DLL loader load these optional dependencies when the DLL is loaded. However I can't find any information on this (perhaps because, as a doze noob, I do not know the correct terminology) in the ctypes documentation. Is there a way to do this in ctypes? Am I going about this in completely the wrong way? Any help or general information about optional DLL dependencies and how they are loaded in windows would be much appreciated. Thanks

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• jQuery class selector oddness

  - by x3sphere

  I'm using jQuery to change the background image of a button depending on the class associated with it on hover. It only works if I put the hover statements in separate functions, however. Why is this? Here's the NON working code, always evaluates to the .submit hover statement, even when that class is removed via the keyup event. $(function() { { $('.submit-getinfo').hover(function () { $(this).css( {backgroundPosition: "right bottom"} ); }, function() { $(this).css( {backgroundPosition: "right top"} ); //$(this).removeClass('submithover'); }); $('.submit').hover(function () { $(this).css( {backgroundPosition: "left bottom"} ); }, function() { $(this).css( {backgroundPosition: "left top"} ); //$(this).removeClass('submithover'); }); }}); Working code: $(function() { { $('.submit').hover(function () { $(this).css( {backgroundPosition: "left bottom"} ); }, function() { $(this).css( {backgroundPosition: "left top"} ); //$(this).removeClass('submithover'); }); }}); $('#test').bind('keyup', function() { if (url == 'devel') { $("#submit").addClass("submit-getinfo").removeClass("submit"); $('.submit-getinfo').hover(function () { $(this).css( {backgroundPosition: "right bottom"} ); }, function() { $(this).css( {backgroundPosition: "right top"} ); //$(this).removeClass('submithover'); }); } } ); I just fail to see why I have to put the hover statements in separate functions, instead of sticking both in the main DOM.

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• Passing C++ object to C++ code through Python?

  - by cornail

  Hi all, I have written some physics simulation code in C++ and parsing the input text files is a bottleneck of it. As one of the input parameters, the user has to specify a math function which will be evaluated many times at run-time. The C++ code has some pre-defined function classes for this (they are actually quite complex on the math side) and some limited parsing capability but I am not satisfied with this construction at all. What I need is that both the algorithm and the function evaluation remain speedy, so it is advantageous to keep them both as compiled code (and preferrably, the math functions as C++ function objects). However I thought of glueing the whole simulation together with Python: the user could specify the input parameters in a Python script, while also implementing storage, visualization of the results (matplotlib) and GUI, too, in Python. I know that most of the time, exposing C++ classes can be done, e.g. with SWIG but I still have a question concerning the parsing of the user defined math function in Python: Is it possible to somehow to construct a C++ function object in Python and pass it to the C++ algorithm? E.g. when I call f = WrappedCPPGaussianFunctionClass(sigma=0.5) WrappedCPPAlgorithm(f) in Python, it would return a pointer to a C++ object which would then be passed to a C++ routine requiring such a pointer, or something similar... (don't ask me about memory management in this case, though :S) The point is that no callback should be made to Python code in the algorithm. Later I would like to extend this example to also do some simple expression parsing on the Python side, such as sum or product of functions, and return some compound, parse-tree like C++ object but let's stay at the basics for now. Sorry for the long post and thx for the suggestions in advance.

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• PHP OO vs Procedure with AJAX

  - by vener

  I currently have a AJAX heavy(almost everything) intranet webapp for a business. It is highly modularized(components and modules ala Joomla), with plenty of folders and files. ~ 80-100 different viewing pages (each very unique in it's own sense) on last count and will likely to increase in the near future. I based around the design around commands and screens, the client request a command and sends the required data and receives the data that is displayed via javascript on the screen. That said, there are generally two types of files, a display files with html, javascript, and a little php for templating. And also a php backend file with a single switch statement with actions such as, save, update and delete and maybe other function. There is very little code reuse. Recently, I have been adding an server sided undo function that requires me to reuse some code. So, I took the chance to try out OOP but I notice that some functions are so simple, that creating a class, retrieving all the data then update all the related rows on the database seems like overkill for a simple action as speed is quite critical. Also I noticed there is only one class in an entire file. So, what if the entire php is a class. So, between creating a class and methods, and using global variables and functions. Which is faster?

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• C# Sql Connection Best Practises 2013

  - by Pete Petersen

  With the new year approaching I'm drawing up a development plan for 2013. I won't bore you with the details but I started thinking about whether the way I do things is actually the 'correct' way. In particular how I'm interfacing with SQL. I create predominantly create WPF desktop applications and often some Silverlight Web Applications. All of my programs are very Data-Centric. When connecting to SQL from WPF I tend to use Stored Procedures stored on the server and fetch them using ADO.NET (e.g. SQLConnection(), .ExecuteQuery()). However with Silverlight I have a WCF service and use LINQ to SQL (and I'm using LINQ much more in WPF). My question is really is am I doing anything wrong in a sense that it's a little old fashioned? I've tried to look this up online but could find anything useful after about 2010 and of those half were 'LINQ is dead!' and the other 'Always use LINQ' Just want to make sure going forward I'm doing the right things the right way, or at least the advised way :). What principles are you using when connecting to SQL? Is it the same for WPF and Silverlight/WCF?

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• Programmatically setup a PEAP connection in Windows Mobile

  - by tomlog

  I have been working on this for a few days and this is doing my head in: Our application is built using the .NET Compact Framework 2.0 and running on Windows Mobile 5 & 6 devices. We can set the WLAN connection of the device programmatically using the Wireless Zero Config functions (described here: msdn.microsoft.com/en-us/library/ms894771.aspx), most notably the WZCSetInterface function which we pinvoke from our application. This works fine for WEP and WPA-PSK connections. In a recent effort to add support for WPA2 networks we decided to modify the code. We have successfully added support for WPA2 which uses a certificate for the 802.1x authentication by setting the correct registry settings before calling WZCSetInterface. Now we want to do the same for WPA2 using PEAP (MS-CHAPv2) authentication. When manually creating such a connection in Windows Mobile the user will be prompted to enter the domain/user/password details. In our application we will have those details stored locally and want to do this all programmatically without any user intervention. So I thought going along the same route as the certificate authentication, setting the correct registry entries before calling WZCSetInterface. The registry settings we set are: \HKCU\Comm\EAP\Config\[ssid name] Enable8021x = 1 (DWORD) LastAuthSuccessful = 1 (DWORD) EapTypeId = 25 (DWORD) Identity = "domain\username" (string) Password = binary blob containing the password that is encrypted using the CryptProtectData function (described here: msdn.microsoft.com/en-us/library/ms938309.aspx) But when these settings are set and I call WZCSetInterface with the correct parameters, it still prompts me with the User Logon dialog asking for the domain/username/password. Has anyone got an idea what I need to do to prevent the password dialog from appearing and connect straight away with the settings stored in the registry?

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• How do I handle freeing unmanaged structures on application close?

  - by LostKaleb

  I have a C# project in which i use several unmanaged C++ functions. More so, I also have static IntPtr that I use as parameters for those functions. I know that whenever I use them, I should implement IDisposable in that class and use a destructor to invoke the Dispose method, where I free the used IntPtr, as is said in the MSDN page. public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } private void Dispose(bool disposing) { // Check to see if Dispose has already been called. if (!this.disposed) { if (disposing) { component.Dispose(); } CloseHandle(m_InstanceHandle); m_InstanceHandle = IntPtr.Zero; disposed = true; } } [System.Runtime.InteropServices.DllImport("Kernel32")] private extern static Boolean CloseHandle(IntPtr handle); However, when I terminate the application, I'm still left with a hanging process in TaskManager. I believe that it must be related to the used of the MarshalAs instruction in my structures: [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public struct SipxAudioCodec { [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)] public string CodecName; public SipxAudioBandwidth Bandwidth; public int PayloadType; } When I create such a structure should I also be careful to free the space it allocs using a destructor? [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public struct SipxAudioCodec { [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)] public string CodecName; public SipxAudioBandwidth Bandwidth; public int PayloadType; ~SipxAudioCodec() { Marshal.FreeGlobal(something...); } }

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• How to find a particular string in a paragraph in android?

  - by user1448108

  In my project the data is stored in html format along with image tag. For example the following data is stored in html format and it contains 2 to 3 images. Mother Teresa as she is commonly known, was born Agnes Gonxha Bojaxhiu. Although born on the 26 August 1910, she considered 27 August, the day she was baptized, to be her "true birthday". “By blood, I am Albanian. By citizenship, an Indian. By faith, I am a Catholic nun. As to my calling, I belong to the world. As to my heart, I belong entirely to the Heart of Jesus." img ----- src="image1.png" ---- Mother Teresa founded the Missionaries of Charity, a Roman Catholic religious congregation, which in 2012 consisted of over 4,500 sisters and is active in 133 countries.img ----- src="image2.png" ----. She was the recipient of numerous honours including the 1979 Nobel Peace Prize. She refused the conventional ceremonial banquet given to laureates, and asked that the $192,000 funds be given to the poor in India. img ----- src="image3.png" ---- Now from the above data I need to find how many images the paragraph has and need to get all the image names along with the extensions and should display them in android. Tried with splitting but did not work. Please help me regarding this. Thanks in advance

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• Debugging scripts loaded with GroovyShell (in eclipse)

  - by MSh

  I am working with eclipse and groovy plug in. I am building a test harness to debug and test groovy scripts. The scripts are really simple but long, most of them just if/else/return. I figured out that I can call them using GroovyShell and Bindings to pass in the values. The problem is that, while I can call the script and get the results just fine, I CAN NOT step in there with the debugger. Breakpoints in those scripts are not active. Is there a way to debug the scripts? Maybe I should use something other than GroovyShell? I really don't want to modify the scripts by wrapping them into functions, and then calling those functions from my test classes. That's how I am using Binding and GroovyShell: def binding = new Binding(); binding.lineList = [list1]; binding.count = 5; def shell = new GroovyShell(binding); def result = shell.evaluate(new File("src/Rules/checkLimit.groovy"));

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• Hashing Function for Map C++

  - by Josh

  I am trying to determine a hash function which takes an input (i, k) and determines a unique solution. The possible inputs for (i, k) range from 0 to 100. Consider each (i, k) as a position of a node in a trinomial tree. Ex: (0, 0) can diverge to (1, 1) (1, 0) (1, -1). (1, 1) can diverge to (2, 2) (2, 1) (2, 0). Sample given here: http://www.google.com/imgres?imgurl=http://sfb649.wiwi.hu-berlin.de/fedc_homepage/xplore/tutorials/stfhtmlimg1156.gif&imgrefurl=http://sfb649.wiwi.hu-berlin.de/fedc_homepage/xplore/tutorials/stfhtmlnode41.html&h=413&w=416&sz=4&tbnid=OegDZu-yeVitZM:&tbnh=90&tbnw=91&zoom=1&usg=__9uQWDNYNLV14YioWWbrqPgfa3DQ=&docid=2hhitNyRWjI_DM&hl=en&sa=X&ei=xAfFUIbyG8nzyAHv2YDICg&ved=0CDsQ9QEwAQ I am using a map map <double, double> hash_table I need a key value to be determined from pairs (i, k) to hash to to value for that (i, k) So far I was only able to come up with linear functions such as: double Hash_function(int i, int k) { //double val = pow(i, k) + i; //return (val % 4294967296); return (i*3.1415 + k*i*9.12341); } However, I cannot determine a unique key with a certain (i, k). What kind of functions can I use to help me do so?

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• Convert VBA to VBS

  - by dnLL

  I have a little VBA script with some functions that I would like to convert to a single VBS file. Here is an example of what I got: Private Declare Function GetPrivateProfileString Lib "kernel32" Alias "GetPrivateProfileStringA" (ByVal lpApplicationName As String, ByVal lpKeyName As Any, ByVal lpDefault As String, ByVal lpReturnedString As String, ByVal nSize As Long, ByVal lpFileName As String) As Long Private Function ReadIniFileString(ByVal Sect As String, ByVal Keyname As String) As String Dim Worked As Long Dim RetStr As String * 128 Dim StrSize As Long Dim iNoOfCharInIni As Integer Dim sIniString, sProfileString As String iNoOfCharInIni = 0 sIniString = "" If Sect = "" Or Keyname = "" Then MsgBox "Erreur lors de la lecture des paramètres dans " & IniFileName, vbExclamation, "INI" Access.Application.Quit Else sProfileString = "" RetStr = Space(128) StrSize = Len(RetStr) Worked = GetPrivateProfileString(Sect, Keyname, "", RetStr, StrSize, IniFileName) If Worked Then iNoOfCharInIni = Worked sIniString = Left$(RetStr, Worked) End If End If ReadIniFileString = sIniString End Function And then, I need to use this function to put some values in strings. VBS doesn't seem to like any of my var declaration ((Dim) MyVar As MyType). If I'm able to adapt that code to VBS, I should be able to do the rest of my functions too. How can I adapt/convert this to VBS? Thank you.

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• Generating python wrapper for 3ed party c++ dll using swig with

  - by MuraliK

  I am new bee to swig. I have a third party c++ dll with the following functions export. I want to call these dll functions in python. So thought of using swig to generate the wrapper using swig. I am not sure what sort of wrapper i need to generate (do i need to generate .lib or .dll to use it in python?). In case i need to generate .dll how do i do that using visual studio 2010. There are some call back function like SetNotifyHandler(void (__stdcall * nf)(int wp, void *lp)) in the bellow list. How do define such function in interface file. can someone help me plese? enter code here #ifndef DLL_H #define DLL_H #ifdef DLL_BUILD #define DLLFUNC __declspec(dllexport) #else #define DLLFUNC __declspec(dllimport) #endif #pragma pack(push) #pragma pack(1) #pragma pack(pop) extern "C" { DLLFUNC int __stdcall StartServer(void); DLLFUNC int __stdcall GetConnectionInfo(int connIndex, Info *buf); DLLFUNC void __stdcall SetNotifyWindow(HWND nw); DLLFUNC void __stdcall SetNotifyHandler(void (__stdcall * nf)(int wp, void *lp)); DLLFUNC int __stdcall SendCommand(int connIndex, Command *cmd); };

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• Templates, Function Pointers and C++0x

  - by user328543

  One of my personal experiments to understand some of the C++0x features: I'm trying to pass a function pointer to a template function to execute. Eventually the execution is supposed to happen in a different thread. But with all the different types of functions, I can't get the templates to work. #include `<functional`> int foo(void) {return 2;} class bar { public: int operator() (void) {return 4;}; int something(int a) {return a;}; }; template <class C> int func(C&& c) { //typedef typename std::result_of< C() >::type result_type; typedef typename std::conditional< std::is_pointer< C >::value, std::result_of< C() >::type, std::conditional< std::is_object< C >::value, std::result_of< typename C::operator() >::type, void> >::type result_type; result_type result = c(); return result; } int main(int argc, char* argv[]) { // call with a function pointer func(foo); // call with a member function bar b; func(b); // call with a bind expression func(std::bind(&bar::something, b, 42)); // call with a lambda expression func( [](void)->int {return 12;} ); return 0; } The result_of template alone doesn't seem to be able to find the operator() in class bar and the clunky conditional I created doesn't compile. Any ideas? Will I have additional problems with const functions?

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• Why is T() = T() allowed?

  - by Rimo

  I believe the expression T() creates an rvalue (by the Standard). However, the following code compiles (at least on gcc4.0): class T {}; int main() { T() = T(); } I know technically this is possible because member functions can be invoked on temporaries and the above is just invoking the operator= on the rvalue temporary created from the first T(). But conceptually this is like assigning a new value to an rvalue. Is there a good reason why this is allowed? Edit: The reason I find this odd is it's strictly forbidden on built-in types yet allowed on user-defined types. For example, int(2) = int(3) won't compile because that is an "invalid lvalue in assignment". So I guess the real question is, was this somewhat inconsistent behavior built into the language for a reason? Or is it there for some historical reason? (E.g it would be conceptually more sound to allow only const member functions to be invoked on rvalue expressions, but that cannot be done because that might break some existing code.)

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• How can one make a 'passthru' function in C++ using macros or metaprogramming?

  - by Ryan

  So I have a series of global functions, say: foo_f1(int a, int b, char *c); foo_f2(int a); foo_f3(char *a); I want to make a C++ wrapper around these, something like: MyFoo::f1(int a, int b, char* c); MyFoo::f2(int a); MyFoo::f3(char* a); There's about 40 functions like this, 35 of them I just want to pass through to the global function, the other 5 I want to do something different with. Ideally the implementation of MyFoo.cpp would be something like: PASSTHRU( f1, (int a, int b, char *c) ); PASSTHRU( f2, (int a) ); MyFoo::f3(char *a) { //do my own thing here } But I'm having trouble figuring out an elegant way to make the above PASSTHRU macro. What I really need is something like the mythical X getArgs() below: MyFoo::f1(int a, int b, char *c) { X args = getArgs(); args++; //skip past implicit this.. ::f1(args); //pass args to global function } But short of dropping into assembly I can't find a good implementation of getArgs().

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• Will C++0x support __stdcall or extern "C" capture-nothing lambdas?

  - by Daniel Trebbien

  Yesterday I was thinking about whether it would be possible to use the convenience of C++0x lambda functions to write callbacks for Windows API functions. For example, what if I wanted to use a lambda as an EnumChildProc with EnumChildWindows? Something like: EnumChildWindows(hTrayWnd, CALLBACK [](HWND hWnd, LPARAM lParam) { // ... return static_cast<BOOL>(TRUE); // continue enumerating }, reinterpret_cast<LPARAM>(&myData)); Another use would be to write extern "C" callbacks for C routines. E.g.: my_class *pRes = static_cast<my_class*>(bsearch(&key, myClassObjectsArr, myClassObjectsArr_size, sizeof(my_class), extern "C" [](const void *pV1, const void *pV2) { const my_class& o1 = *static_cast<const my_class*>(pV1); const my_class& o2 = *static_cast<const my_class*>(pV2); int res; // ... return res; })); Is this possible? I can understand that lambdas that capture variables will never be compatible with C, but it at least seems possible to me that capture-nothing lambdas can be compatible.

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• Concept: Information Into Memory Location.

  - by Richeve S. Bebedor

  I am having troubles conceptualizing an algorithm to be used to transform any information or data into a specific appropriate and reasonable memory location in any data structure that I will be devising. To give you an idea, I have a JPanel object instance and I created another Container type object instance of any subtype (note this is in Java because I love this language), then I collected those instances into a data structure not specifically just for those instances but also applicable to any type of object. Now my procedure for fetching those data again is to extract the object specific features similar in category to all object in that data structure and transform it into a integer data memory location (specifically as much as possible) or any type of data that will pertain to this transformation. And I can already access that memory location without further sorting or applications of O(n) time complex algorithms (which I think preferable but I wanted to do my own way XD). The data structure is of any type either binary tree, linked list, arrays or sets (and the like XD). What is important is I don't need to have successive comparing and analysis of data just to locate information in big structures. To give you a technical idea, I have to an array DS that contains JLabel object instance with a specific name "HelloWorld". But array DS contains other types of object (in multitude). Now this JLabel object has a location in the array at index [124324] (which is if you do any type of searching algorithm just to arrive at that location is conceivably slow because added to it the data structure used was an array *note please disregard the efficiency of the data structure to be used I just want to explain to you my concept XD). Now I want to equate "HelloWorld" to 124324 by using a conceptually made function applicable to all data types. So that I can do a direct search by doing this DS[extractLocation("HelloWorld")] just to get that JLabel instance. I know this may sound crazy but I want to test my concept of non-sorting feature extracting search algorithm for any data structure wherein my main problem is how to transform information to be stored into memory location of where it was stored.

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• select nodes from a line of xml code with sql

  - by wondergoat77

  I have a table that stores a huge line/entire document of xml like this: <?xml version="1.0" encoding="utf-16"?> <RealQuestResponse xmlns:xsi="http://www.w3.org /2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <Success>true</Success> <Subject> <AmbiguousMatches /> <Assessment> <LandValue>0</LandValue> <ImprovementsValue>0</ImprovementsValue> <TotalValue>0</TotalValue> </Assessment> <RecentSales /> <Warnings> <Score>0</Score> <TrusteesDeedRatio>0</Tr........etc Is there a way to pull any of these fields out of the xml? it is stored in a column in a table called AutomatedRequests That table looks like this: requestid Provider Date Success Response 1 test 1/2/2012 Y <?xml version..... <---this is the xml code stored> Ive seen a couple ways but nothing like this Id basically like something like select xmlnode1, xmlnode2, xmlnode3 from automatedrequests have tried this but not working: select xml.query('RealQuestResponse/Bedrooms/*') from automatedRequests where orderid = 1266162

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