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• Adding web reference is not generating the expected reference.cs file. Absent functions.

  - by user48408

  I'm working with an old windows app in visual studio 2005. A webserviced referenced in the original app has 2 functions and when i peak inside the auto-generated reference.cs file I notice a couple of other functions to allow async calls have been geenrated i.e. BeginWhateverFunctionNameIsCalled and EndWhateverFunctionNameIsCalled. My problem is that I've created a new windows app and added the same web references but the Begin and End functions are not generated in my reference.cs proxy class. Anyone know whats going on?

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• C++: get const or non-const reference type from trait

  - by maciekp

  I am writing a functor F which takes function of type void (*func)(T) and func's argument arg. Then functor F calls func with arg. I would like F not to copy arg, just to pass it as reference. But then I cannot simply write "void F(void (*func)(T), T&)" because T could be a reference. So I am trying to write a trait, which allows to get proper reference type of T: T -> T& T& -> T& const T -> const T& const T& -> const T& I come up with something like this: template<typename T> struct type_op { typedef T& valid_ref_type; }; template<typename T> struct type_op<T&> { typedef typename type_op<T>::valid_ref_type valid_ref_type; }; template<typename T> struct type_op<const T> { typedef const T& valid_ref_type; }; template<typename T> struct type_op<const T&> { typedef const T& valid_ref_type; }; Which doesn't work for example for void a(int x) { std::cout << x << std::endl; } F(&a, 7); Giving error: invalid initialization of non-const reference of type ‘int&’ from a temporary of type ‘int’ in passing argument 2 of ‘void f(void (*)(T), typename type_op::valid_ref_type) [with T = int]’ How to get this trait to work?

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• [Perl] Retrieve the reference

  - by Sebastian

  Hello, with the hash below, I would like the clients array's reference : my $this = { 'name' => $name, 'max_clients' => $max_clients, 'clients' => () }; I can't do "\$this{'clients'};" to retrieve the reference.

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• How to get Ponter/Reference semantics in Scala.

  - by Lukasz Lew

  In C++ I would just take a pointer (or reference) to arr[idx]. In Scala I find myself creating this class to emulate a pointer semantic. class SetTo (val arr : Array[Double], val idx : Int) { def apply (d : Double) { arr(idx) = d } } Isn't there a simpler way? Doesn't Array class have a method to return some kind of reference to a particular field?

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• System.Threading.Timer keep reference to it.

  - by Daniel Bryars

  According to [http://msdn.microsoft.com/en-us/library/system.threading.timer.aspx][1] you need to keep a reference to a System.Threading.Timer to prevent it from being disposed. I've got a method like this: private void Delay(Action action, Int32 ms) { if (ms <= 0) { action(); } System.Threading.Timer timer = new System.Threading.Timer( (o) => action(), null, ms, System.Threading.Timeout.Infinite); } Which I don't think keeps a reference to the timer, I've not seen any problems so far, but that's probably because the delay periods used have been pretty small. Is the code above wrong? And if it is, how to I keep a reference to the Timer? I'm thinking something like this might work: class timerstate { internal volatile System.Threading.Timer Timer; }; private void Delay2(Action action, Int32 ms) { if (ms <= 0) { action(); } timerstate state = new timerstate(); lock (state) { state.Timer = new System.Threading.Timer( (o) => { lock (o) { action(); ((timerstate)o).Timer.Dispose(); } }, state, ms, System.Threading.Timeout.Infinite); } The locking business is so I can get the timer into the timerstate class before the delegate gets invoked. It all looks a little clunky to me. Perhaps I should regard the chance of the timer firing before it's finished constructing and assigned to the property in the timerstace instance as negligible and leave the locking out.

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• Change dynamic web reference from web./app.config

  - by Snæbjørn

  I have a problem changing a dynamic web reference in the config file. Changing the url in the config file doesn't have any effect. I have to change the url in .settings and compile for it to change. I added the web reference using the wizard. Set the URL behavior to dynamic, which added the relevant XML tags in config file. In my solution I have the web API (web reference) in a separate project (class lib), so I referenced the project and copied the <applicationSettings> over. <applicationSettings> <StartupProject.Properties.Settings> <setting name="WebReference" serializeAs="String"> <value>http://someurl/somefile.asmx</value> </setting> </StartupProject.Properties.Settings> </applicationSettings> Note that it's <StartupProject.Properties.Settings> and not <WebRefProject.Properties.Settings>. Are there some limitations I'm not aware of or am I doing something wrong?

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• AS 3.0 reference problem

  - by vasion

  I am finding it hard to fugure out the reference system in AS 3.0. this is the code i have (i have trimmed it down in order to find the problem but to no avail) package rpflash.ui { import flash.display.Sprite; import flash.display.MovieClip; import flash.display.Stage; import nowplaying; import flash.text.TextField; public class RPUserInterface extends Sprite{ var np:nowplaying; public function RPUserInterface(){ } public function init(){ var np:nowplaying = new nowplaying(); this.addChild(np) } public function updateplayer(xml:XML){ var artist: String = xml.nowplaying.artist.toString(); var title: String = xml.nowplaying.title.toString(); trace("UI:update"); trace(this.np);// this gives me a null reference } } } and still i cannot access np!!! trace this.np gives me a null reference. i am not even trying to access it from a subling class. (btw i def want to know how to do that as well.)

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• Reference 3.5 assembly from 4.0 winforms phail

  - by Dean Lunz

  So I have this utility library that is compiled as a dll under .net 3.5 and it is used by my asp.net 3.5 website. I created a .net 4.0 winforms app to push data onto the website. I want to make use of the functionality in the utilities library from this winforms app. The problem lies in that when I make reference to the utilities library and use the code in it intellisense barks at me saying that it can't find the objects in that library. The thing is I would switch the winforms app to 3.5 which fixes the problem, but I am using Tasks which require 4.0. And because my website and utilities library both run 3.5 and my website is hosted at godaddy that currently only supports asp.net 3.5 so compiling my utilities library under 4.0 for my winforms app is not going to work because it breaks my website. I have tried the app.config trick ala useLegacyV2RuntimeActivationPolicy="true" ... But that did not help. Obviously I could start a new utilities project for 4.0 and and copy the code files from the existing utilities library then reference the new 4.0 utilities library in my winforms app but, that strikes me as being rather overkill when all I want to do is reference the library and use it's functionality. Not to mention that I would have two utility libraries both containing the exact same code, and if I update the code in one I will need to make sure that the other is also updated. I could use add file as link, but you get the idea. So is there anything else I could try or any other way to solve or get around this? Or am I just going to have to break down and create a identical clone of the utilities library for 4.0.

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• Variable reference problem when loading an object from a file in Java

  - by Snail

  I have a problem with the reference of a variable when loading a saved serialized object from a data file. All the variables referencing to the same object doesn't seem to update on the change. I've made a code snipped below that illustrates the problem. Tournament test1 = new Tournament(); Tournament test2 = test1; try { FileInputStream fis = new FileInputStream("test.out"); ObjectInputStream in = new ObjectInputStream(fis); test1 = (Tournament) in.readObject(); in.close(); } catch (IOException ex){ Logger.getLogger(Frame.class.getName()).log(Level.SEVERE, null, ex); } catch (ClassNotFoundException ex){ Logger.getLogger(Frame.class.getName()).log(Level.SEVERE, null, ex); } System.out.println("test1: " + test1); System.out.println("test2: " + test2); After this code is ran test1 and test2 doesn't reference to the same object anymore. To my knowledge they should do that since in the declaration of test2 makes it a reference to test1. When test1 is updated test2 should reflect the change and return the new object when called in the code. Am I missing something essential here or have I been misstaught about how the variable references in Java works?

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• Give a reference to a python instance attribute at class definition

  - by Guenther Jehle

  I have a class with attributes which have a reference to another attribute of this class. See class Device, value1 and value2 holding a reference to interface: class Interface(object): def __init__(self): self.port=None class Value(object): def __init__(self, interface, name): self.interface=interface self.name=name def get(self): return "Getting Value \"%s\" with interface \"%s\""%(self.name, self.interface.port) class Device(object): interface=Interface() value1=Value(interface, name="value1") value2=Value(interface, name="value2") def __init__(self, port): self.interface.port=port if __name__=="__main__": d1=Device("Foo") print d1.value1.get() # >>> Getting Value "value1" with interface "Foo" d2=Device("Bar") print d2.value1.get() # >>> Getting Value "value1" with interface "Bar" print d1.value1.get() # >>> Getting Value "value1" with interface "Bar" The last print is wrong, cause d1 should have the interface "Foo". I know whats going wrong: The line interface=Interface() line is executed, when the class definition is parsed (once). So every Device class has the same instance of interface. I could change the Device class to: class Device(object): interface=Interface() value1=Value(interface, name="value1") value2=Value(interface, name="value2") def __init__(self, port): self.interface=Interface() self.interface.port=port So this is also not working: The values still have the reference to the original interface instance and the self.interface is just another instance... The output now is: >>> Getting Value "value1" with interface "None" >>> Getting Value "value1" with interface "None" >>> Getting Value "value1" with interface "None" So how could I solve this the pythonic way? I could setup a function in the Device class to look for attributes with type Value and reassign them the new interface. Isn't this a common problem with a typical solution for it? Thanks!

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• How do I use an index in an array reference as a method reference in Perl?

  - by Robert P

  Similar to this question about iterating over subroutine references, and as a result of answering this question about a OO dispatch table, I was wondering how to call a method reference inside a reference, without removing it first, or if it was even possible. For example: package Class::Foo; use 5.012; #Yay autostrict! use warnings; # a basic constructor for illustration purposes.... sub new { my $class = shift; return bless {}, $class; } # some subroutines for flavor... sub sub1 { say 'in sub 1' } sub sub2 { say 'in sub 2' } sub sub3 { say 'in sub 3' } # and a way to dynamically load the tests we're running... sub sublist { my $self = shift; return [ $self->can('sub1'); $self->can('sub3'}; $self->can('sub2'); ]; } package main; my $instance = Class::Foo->new(a => 1, b => 2, c => 3); my $tests = $instance->sublist(); my $index = int(rand($#{$tests})); # <-- HERE So, at HERE, we could do: my $ref = $tests->{$index}; $instance->$ref(); but how would we do this, without removing the reference first?

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• How to reference SMF libraries when deploying on phone 7 (Release)

  - by aHaH

  Initially, at Visual Studio, I clicked debug instead of release to deploy my app on phone 7 device. No errors, works perfectly fine! Received multitude of errors that mention that some of the libraries don't seem to exist on the mobile phone. For example, extract from the entire list of errors include Warning 10 The referenced component 'Microsoft.SilverlightMediaFramework.Utilities' could not be found. Warning 3 Could not resolve this reference. Could not locate the assembly "Microsoft.SilverlightMediaFramework.Plugins". Check to make sure the assembly exists on disk. If this reference is required by your code, you may get compilation errors. SLARToolKitWinPhoneSample In addition, im also using Slartookit to power up the AR capabilities. Deploying (Release) on the mobile prompts the following errors too. Error 11 The type or namespace name 'SLARToolKit' could not be found (are you missing a using directive or an assembly reference?) What should I do? Will updating the mobile solve this? Do I have to manually install? Or? Thanks

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• Visual C++ 2010, rvalue reference bug?

  - by Sergey Shandar

  Is it a bug in Visual C++ 2010 or right behaviour? template<class T> T f(T const &r) { return r; } template<class T> T f(T &&r) { static_assert(false, "no way"); return r; } int main() { int y = 4; f(y); } I thought, the function f(T &&) should never be called but it's called with T = int &. The output: main.cpp(10): error C2338: no way main.cpp(17) : see reference to function template instantiation 'T f<int&>(T)' being compiled with [ T=int & ] Update 1 Do you know any C++x0 compiler as a reference? I've tried comeau online test-drive but could not compile r-value reference. Update 2 Workaround (using SFINAE): #include <boost/utility/enable_if.hpp> #include <boost/type_traits/is_reference.hpp> template<class T> T f(T &r) { return r; } template<class T> typename ::boost::disable_if< ::boost::is_reference<T>, T>::type f(T &&r) { static_assert(false, "no way"); return r; } int main() { int y = 4; f(y); // f(5); // generates "no way" error, as expected. }

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• Write-Only Reference in C++?

  - by Robert Mason

  Is there a way to code a write-only reference to an object? For example, suppose there was a mutex class: template <class T> class mutex { protected: T _data; public: mutex(); void lock(); //locks the mutex void unlock(); //unlocks the mutex T& data(); //returns a reference to the data, or throws an exception if lock is unowned }; Is there a way to guarantee that one couldn't do this: mutex<type> foo; T& ref; foo.lock(); ref = foo.data(); foo.unlock(); //I have a unguarded reference to foo now On the other hand, is it even worth it? I know that some people assume that programmers won't deliberately clobber the system, but then, why do we have private variables in the first place, eh? It'd be nice to just say it's "Undefined Behavior", but that just seems a little bit too insecure.

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• Reference problem when returning an object from array in PHP

  - by avastreg

  I've a reference problem; the example should be more descriptive than me :P I have a class that has an array of objects and retrieve them through a key (string), like an associative array: class Collection { public $elements; function __construct() { $this->elements = array(); } public function get_element($key) { foreach($this->elements as $element) { if ($element->key == $key) { return $element; break; } } return null; } public function add_element ($element) { $this->elements[] = $element; } } Then i have an object (generic), with a key and some variables: class Element { public $key; public $another_var; public function __construct($key) { $this->key = $key; $this->another_var = "default"; } } Now, i create my collection: $collection = new Collection(); $collection->add_element(new Element("test1")); $collection->add_element(new Element("test2")); And then i try to change variable of an element contained in my "array": $element = $collection->get_element("test1"); $element->another_var = "random_string"; echo $collection->get_element("test1")->another_var; Ok, the output is random_string so i know that my object is passed to $element in reference mode. But if i do, instead: $element = $collection-get_element("test1"); $element = null; //or $element = new GenericObject(); $element-another_var = "bla"; echo $collection-get_element("test1")-another_var; the output is default like if it lost the reference. So, what's wrong? I have got the references to the variables of the element and not to the element itself? Any ideas?

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• Strange compilation error on reference passing argument to function

  - by Grewdrewgoo Goobergabbsoen

  Here's the code: #include <iostream> using namespace std; void mysize(int &size, int size2); int main() { int *p; int val; p = &val; cout << p; mysize(&val, 20); // Error is pointed here! } void mysize(int &size, int size2) { cout << sizeof(size); size2 = size2 + 6000; cout << size2; } Here's the error output from GCC: In function 'int main()': Line 10: error: invalid initialization of non-const reference of type 'int&' from a temporary of type 'int*' compilation terminated due to -Wfatal-errors. What does that imply? I do not understand the error message ... invalid initialization of a non-constant? I declared the prototype function above with two parameters to take, one a reference of an integer and one just an integer value itself. I passed the reference of the int (see line 10), yet this error keeps being thrown at me. What is the issue?

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• C++ invalid reference problem

  - by Karol

  Hi all, I'm writing some callback implementation in C++. I have an abstract callback class, let's say: /** Abstract callback class. */ class callback { public: /** Executes the callback. */ void call() { do_call(); }; protected: /** Callback call implementation specific to derived callback. */ virtual void do_call() = 0; }; Each callback I create (accepting single-argument functions, double-argument functions...) is created as a mixin using one of the following: /** Makes the callback a single-argument callback. */ template <typename T> class singleArgumentCallback { protected: /** Callback argument. */ T arg; public: /** Constructor. */ singleArgumentCallback(T arg): arg(arg) { } }; /** Makes the callback a double-argument callback. */ template <typename T, typename V> class doubleArgumentCallback { protected: /** Callback argument 1. */ T arg1; /** Callback argument 2. */ V arg2; public: /** Constructor. */ doubleArgumentCallback(T arg1, V arg2): arg1(arg1), arg2(arg2) { } }; For example, a single-arg function callback would look like this: /** Single-arg callbacks. */ template <typename T> class singleArgFunctionCallback: public callback, protected singleArgumentCallback<T> { /** Callback. */ void (*callbackMethod)(T arg); public: /** Constructor. */ singleArgFunctionCallback(void (*callback)(T), T argument): singleArgumentCallback<T>(argument), callbackMethod(callback) { } protected: void do_call() { this->callbackMethod(this->arg); } }; For user convenience, I'd like to have a method that creates a callback without having the user think about details, so that one can call (this interface is not subject to change, unfortunately): void test3(float x) { std::cout << x << std::endl; } void test5(const std::string& s) { std::cout << s << std::endl; } make_callback(&test3, 12.0f)->call(); make_callback(&test5, "oh hai!")->call(); My current implementation of make_callback(...) is as follows: /** Creates a callback object. */ template <typename T, typename U> callback* make_callback( void (*callbackMethod)(T), U argument) { return new singleArgFunctionCallback<T>(callbackMethod, argument); } Unfortunately, when I call make_callback(&test5, "oh hai!")->call(); I get an empty string on the standard output. I believe the problem is that the reference gets out of scope after callback initialization. I tried using pointers and references, but it's impossible to have a pointer/reference to reference, so I failed. The only solution I had was to forbid substituting reference type as T (for example, T cannot be std::string&) but that's a sad solution since I have to create another singleArgCallbackAcceptingReference class accepting a function pointer with following signature: void (*callbackMethod)(T& arg); thus, my code gets duplicated 2^n times, where n is the number of arguments of a callback function. Does anybody know any workaround or has any idea how to fix it? Thanks in advance!

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• Oracle VM Blade Cluster Reference Configuration

  - by Ferhat Hatay

  Today we are happy to announce the availability of the Oracle VM blade cluster reference configuration for Sun Blade 6000 modular systems.  The new Oracle VM blade cluster reference configuration can help reduce the time to deploy virtual infrastructure by up to 98 percent when compared to multi-vendor configurations. Oracle's virtualization strategy is to simplify the deployment, management, and support of the enterprise stack from application to disk. The Oracle VM blade cluster reference configuration is a single-vendor solution that addresses every layer of the virtualization stack with Oracle hardware and software components. It enables quick and easy deployment of the virtualized infrastructure using components that have been tested together and are all supported together by one vendor — Oracle. All components listed in the reference configuration have been tested together by Oracle, reducing the need for customer testing and the time-consuming and complex effort of designing and deploying a stable configuration. Benefitting from pre-installed Oracle VM Server for x86 software on Oracle’s highly scalable and reliable Sun Blade servers with built-in networking and Oracle’s Sun ZFS Storage Appliance product line, the configuration provides high availability via the blade cluster as well as a documented best practice guide that helps reduce deployment time and cost for customers implementing highly virtualized applications or private cloud Infrastructure as a Service (IaaS) architectures. To further support easier, faster and lower-cost deployments, Oracle Linux, Oracle Solaris and Oracle VM are available for pre-install on select Sun x86 systems, and Oracle VM Templates are available for download for Oracle Applications, Oracle Fusion Middleware, Oracle Database, Oracle Real Application Clusters, and many other Oracle products. Key benefits of the Oracle VM blade cluster reference configuration include: Faster time to value – Begin deploying applications immediately because the optimized software stack is pre-configured for best practices and is ready-to-run on the recommended hardware platforms. Reduced deployment cost and risk – The entire hardware and software stack has been tested and is supported together by Oracle. Elastic scalability – As capacity needs grow, the system can be easily scaled in multiple dimensions with the ability to add compute, storage, and networking resources independently. For more information, see: Oracle white paper: Accelerating deployment of virtualized infrastructures with the Oracle VM blade cluster reference configuration Oracle technical white paper: Best Practices and Guidelines for Deploying the Oracle VM Blade Cluster Reference Configuration

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• Verifying method with array passed by reference using Moq

  - by kaa

  Given the following interface public interface ISomething { void DoMany(string[] strs); void DoManyRef(ref string[] strs); } I would like to verify that the DoManyRef method is called, and passed any string array as the strs parameter. The following test fails: public void CanVerifyMethodsWithArrayRefParameter() { var a = new Mock<ISomething>().Object; var strs = new string[0]; a.DoManyRef(ref strs); var other = It.IsAny<string[]>(); Mock.Get(a).Verify(t => t.DoManyRef(ref other)); } While the following not requiring the array passed by reference passes: public void CanVerifyMethodsWithArrayParameter() { var a = new Mock<ISomething>().Object; a.DoMany(new[] { "a", "b" }); Mock.Get(a).Verify(t => t.DoMany(It.IsAny<string[]>())); } I am not able to change the interface to eliminate the by reference requirement.

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• Pass-by-Reference Error

  - by TK

  I have a hook system setup... which is working on localhost... I put it live and get an error saying "Warning: Call-time pass-by-reference has been deprecated". Now, apparently the work around is to remove all "&" from your function calls, ie foo(&$me) to foo($me) and then in foo's function definition do "function foo(&$me)". However, I can not do this... because my hooks accept an array as arguments, I need a work around for this. Like I can use "run_hooks ( 'hook-name', $me );" or "run_hooks ( 'hook-name', array ( $me, $another_var, etc... ) )"; So this means I can not use "function run_hooks ( $hook_name, &$arguments )" because I'll get an error in php saying it can not pass "array()" as reference... Any ideas an a work around? Thanks.

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• PHP Call Time Pass Reference

  - by user275074

  What is Call Time Pass Reference? What does it do?

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• Is there any UML reference card available?

  - by csharpbaby

  Are any reference card or cheat sheet available for UML?

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• Errors/warnings passing int/char arrays by reference

  - by Ankur Banerjee

  I'm working on a program where I try to pass parameters by reference. I'm trying to pass a 2D int array and a 1D char array by reference. Function prototype: void foo (int* (&a)[2][2], char* (&b)[4]) Function call: foo (a, b); However, when I compile the code with -ansi and -Wall flags on gcc, I get the following errors: foo.c: At top level: error: expected ‘)’ before ‘&’ token error: expected ‘;’, ‘,’ or ‘)’ before ‘char’ foo.c: In function ‘main’: error: too many arguments to function ‘foo’ I've stripped out the rest of the code of my program and concentrated on the bits which throw up the errors. I've searched around on StackOverflow and tried out different ways to pass the parameters, but none of them seem to work. (I took this way of passing parameters from the discussion on StackOverflow here.) Could you please tell me where I'm going wrong?

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• make reference to an empty query in flex

  - by Adam

  a bit of a dumb questions I'm sure I'm trying to allow user to set an item to be default. I've got a function that run a query to first find the current default item. Then runs a second query that unsets the current default item. Then a third query runs to set the new user selected item to be the default. This seem to work fine when a default item has been perviously selected, but when I try to set the default item initially I get the good old "Cannot access a property or method of a null object reference." error. This is because the first query that runs returns no items I'm sure. So I need to write an if statement that if the first query returns nothing to skip the second and go right to the third. The only problem is I can't make a reference to a null object. So how do I go about writing this statement. Thanks

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• compile time if && return string reference optimization

  - by Truncheon

  Hi. I'm writing a series classes that inherit from a base class using virtual. They are INT, FLOAT and STRING objects that I want to use in a scripting language. I'm trying to implement weak typing, but I don't want STRING objects to return copies of themselves when used in the following way (instead I would prefer to have a reference returned which can be used in copying): a = "hello "; b = "world"; c = a + b; I have written the following code as a mock example: #include <iostream> #include <string> #include <cstdio> #include <cstdlib> std::string dummy("<int object cannot return string reference>"); struct BaseImpl { virtual bool is_string() = 0; virtual int get_int() = 0; virtual std::string get_string_copy() = 0; virtual std::string const& get_string_ref() = 0; }; struct INT : BaseImpl { int value; INT(int i = 0) : value(i) { std::cout << "constructor called\n"; } INT(BaseImpl& that) : value(that.get_int()) { std::cout << "copy constructor called\n"; } bool is_string() { return false; } int get_int() { return value; } std::string get_string_copy() { char buf[33]; sprintf(buf, "%i", value); return buf; } std::string const& get_string_ref() { return dummy; } }; struct STRING : BaseImpl { std::string value; STRING(std::string s = "") : value(s) { std::cout << "constructor called\n"; } STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } bool is_string() { return true; } int get_int() { return atoi(value.c_str()); } std::string get_string_copy() { return value; } std::string const& get_string_ref() { return value; } }; struct Base { BaseImpl* impl; Base(BaseImpl* p = 0) : impl(p) {} ~Base() { delete impl; } }; int main() { Base b1(new INT(1)); Base b2(new STRING("Hello world")); Base b3(new INT(*b1.impl)); Base b4(new STRING(*b2.impl)); std::cout << "\n"; std::cout << b1.impl->get_int() << "\n"; std::cout << b2.impl->get_int() << "\n"; std::cout << b3.impl->get_int() << "\n"; std::cout << b4.impl->get_int() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_ref() << "\n"; std::cout << b2.impl->get_string_ref() << "\n"; std::cout << b3.impl->get_string_ref() << "\n"; std::cout << b4.impl->get_string_ref() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_copy() << "\n"; std::cout << b2.impl->get_string_copy() << "\n"; std::cout << b3.impl->get_string_copy() << "\n"; std::cout << b4.impl->get_string_copy() << "\n"; return 0; } It was necessary to add an if check in the STRING class to determine whether its safe to request a reference instead of a copy: Script code: a = "test"; b = a; c = 1; d = "" + c; /* not safe to request reference by standard */ C++ code: STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } If was hoping there's a way of moving that if check into compile time, rather than run time.

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