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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • How to access the element of a list/vector that passed by reference in C++

    - by bsoundra
    Hi all, The problem is passing lists/vectors by reference int main(){ list<int> arr; //Adding few ints here to arr func1(&arr); return 0; } void func1(list<int> * arr){ // How Can I print the values here ? //I tried all the below , but it is erroring out. cout<<arr[0]; // error cout<<*arr[0];// error cout<<(*arr)[0];//error //How do I modify the value at the index 0 ? func2(arr);// Since it is already a pointer, I am passing just the address } void func2(list<int> *arr){ //How do I print and modify the values here ? I believe it should be the same as above but // just in case. } Is the vectors any different from the lists ? Thanks in advance. Any links where these things are explained elaborately will be of great help. Thanks again.

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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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  • Passing char * into fopen with C.

    - by Rhys
    Hey there, I'm writing a program that passes data from a file into an array, but I'm having trouble with fopen (). It seems to work fine when I hardcode the file path into the parameters (eg fopen ("data/1.dat", "r");) but when I pass it as a pointer, it returns NULL. Note that line 142 will print "data/1.dat" if entered from command line so parse_args () appears to be working. 132 int 133 main(int argc, char **argv) 134 { 135 FILE *in_file; 136 int *nextItem = (int *) malloc (sizeof (int)); 137 set_t *dictionary; 138 139 /* Parse Arguments */ 140 clo_t *iopts = parse_args(argc, argv); 141 142 printf ("INPUT FILE: %s.\n", iopts->input_file); /* This prints correct path */ 143 /* Initialise dictionary */ 144 dictionary = set_create (SET_INITAL_SIZE); 145 146 /* Use fscanf to read all data values into new set_t */ 147 if ((in_file = fopen (iopts->input_file, "r")) == NULL) 148 { 149 printf ("File not found...\n"); 150 return 0; 151 } Thanks! Rhys

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  • Passing Variables between views / view controllers

    - by Dan
    Hi I'm new to ObjectiveC / IPhoneSDK and I'm informally trying to study it on my own. What I'm basically trying to do is from one view there are 12 zodiac signs. When a user clicks one, it proceeds to the second view (with animation) and loads the name of the zodiac sign it clicked in a UILabel, that's it. Here are my codes: Lovescopes = 1st page Horoscopes = 2nd page Lovescopes4AppDelegate.h #import <UIKit/UIKit.h> #import "HoroscopesViewController.h" #import "Lovescopes4AppDelegate.h" @class Lovescopes4ViewController; @interface Lovescopes4AppDelegate : NSObject <UIApplicationDelegate> { UIWindow *window; Lovescopes4ViewController *viewController; HoroscopesViewController *horoscopesViewController; } -(void)loadHoroscope; -(void)loadMainPage; @property (nonatomic, retain) IBOutlet UIWindow *window; @property (nonatomic, retain) IBOutlet Lovescopes4ViewController *viewController; @property (nonatomic, retain) HoroscopesViewController *horoscopesViewController; @end Lovescopes4AppDelegate.m #import "Lovescopes4AppDelegate.h" #import "Lovescopes4ViewController.h" @implementation Lovescopes4AppDelegate @synthesize window; @synthesize viewController; @synthesize horoscopesViewController; -(void)loadHoroscope { HoroscopesViewController *aHoroscopeViewController = [[HoroscopesViewController alloc] initWithNibName:@"HoroscopesViewController" bundle:nil]; [self setHoroscopesViewController:aHoroscopeViewController]; [aHoroscopeViewController release]; [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:0.5]; [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft forView:window cache:YES]; [viewController.view removeFromSuperview]; [self.window addSubview:[horoscopesViewController view]]; [UIView commitAnimations]; } -(void)loadMainPage { [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:0.5]; [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromRight forView:window cache:NO]; [horoscopesViewController.view removeFromSuperview]; [self.window addSubview:[viewController view]]; [UIView commitAnimations]; [horoscopesViewController release]; horoscopesViewController = nil; } - (void)applicationDidFinishLaunching:(UIApplication *)application { // Override point for customization after app launch [window addSubview:viewController.view]; [window makeKeyAndVisible]; } - (void)dealloc { [viewController release]; [window release]; [super dealloc]; } @end Lovescopes4ViewController.h #import <UIKit/UIKit.h> #import "HoroscopesViewController.h" @interface Lovescopes4ViewController : UIViewController { HoroscopesViewController *hvc; } -(IBAction)loadAries; @property (nonatomic, retain) HoroscopesViewController *hvc; @end Lovescope4ViewController.m #import "Lovescopes4ViewController.h" #import "Lovescopes4AppDelegate.h" @implementation Lovescopes4ViewController @synthesize hvc; -(IBAction)loadAries { NSString *selected =@"Aries"; [hvc loadZodiac:selected]; Lovescopes4AppDelegate *mainDelegate = (Lovescopes4AppDelegate *) [[UIApplication sharedApplication] delegate]; [mainDelegate loadHoroscope]; } HoroscopesViewController.h #import <UIKit/UIKit.h> @interface HoroscopesViewController : UIViewController { IBOutlet UILabel *zodiacLabel; } -(void)loadZodiac:(id)zodiacSign; -(IBAction)back; @property (nonatomic, retain) IBOutlet UILabel *zodiacLabel; @end HoroscopesViewController.m #import "HoroscopesViewController.h" #import "Lovescopes4AppDelegate.h" @implementation HoroscopesViewController @synthesize zodiacLabel; /* // The designated initializer. Override if you create the controller programmatically and want to perform customization that is not appropriate for viewDidLoad. - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) { // Custom initialization } return self; } */ /* // Implement viewDidLoad to do additional setup after loading the view, typically from a nib. - (void)viewDidLoad { [super viewDidLoad]; } */ /* // Override to allow orientations other than the default portrait orientation. - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { // Return YES for supported orientations return (interfaceOrientation == UIInterfaceOrientationPortrait); } */ -(void)loadZodiac:(id)zodiacSign { zodiacLabel.text = [NSString stringWithFormat: @"%@", zodiacSign]; } -(IBAction)back { Lovescopes4AppDelegate *mainDelegate = (Lovescopes4AppDelegate *) [[UIApplication sharedApplication] delegate]; [mainDelegate loadMainPage]; }

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  • passing a variable to a ajax request Jquery

    - by user304735
    Hello, I am trying to pass a variable to an ajax request via jquery. I have a triggered event that defines the variable. I want to do this so that I can have one ajax request handle multiple urls. I have alerted the url and it come back fine, but when I plug it into the URL slot of a $.ajax request my targeted content does not load. Here is my code. $(document).ready(function(){ $('a').live('click', function(){ var link = $(this).attr("href"); $.ajax({ url: link, success: function(html){ $('#load').html(html) } }); }); }); this has been a real headache and I feel I am just misusing something. Please help.

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  • CakePHP passing parameters to action

    - by iancocco
    Hi im kinda new in cakephp and having a lot of trouble adjusting.. Here's my biggest problem .. Im trying to pass a parameter to an action, it does load, but when my script goes from the controller to the view, and goes back to the controller again, its gone. CONTROLLER CODE function add($mac = 0) { if(isset($this->params['form']['medico'])) { $temp= $this->Person->find('first', array('conditions' => array('smartphones_MAC' => $mac))); $id= $temp['Person']['id']; $this->Union->set('events_id', $id+1); $this->Union->set('people_id', $id); $this->Union->save(); } VIEW CODE (This is a menu, i only have one button right now) <fieldset> <legend>SELECCIONE SU ALERTA</legend> <?php echo $form->create('Event'); echo $form->submit('EMERGENCIA MEDICA',array('name'=>'medico')); echo $form->end(); ?> </fieldset>

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  • Passing list and dictionary type parameter with Python

    - by prosseek
    When I run this code def func(x, y, *w, **z): print x print y if w: print w if z: print z else: print "None" func(10,20, 1,2,3,{'k':'a'}) I get the result as follows. 10 20 (1, 2, 3, {'k': 'a'}) None But, I expected as follows, I mean the list parameters (1,2,3) matching *w, and dictionary matching **z. 10 20 (1,2,3) {'k':'a'} Q : What went wrong? How can I pass the list and dictionary as parameters? Added func(10,20, 10,20,30, k='a') seems to be working

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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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  • Passing a value from child window to parent

    - by gnomixa
    Here is my scenario: i have a parent web page, in my javascript code I open a new window. This new window is a server-side aspx page. This child page needs to save some data in the database, and after saving it returns an ID. Now, I need to pass this ID from the child server page to the parent's javascript. Essentially I need the child server code to trigger: 1) return the value to the javascript code of the parent page 2) close itself What would be the acceptable way to do it?

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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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  • Passing arguments to a C program

    - by Radhika
    Hi All, I was writing a C program where I use 6 variables a,b,c,d,e,f a,b,c are constant values which I should pass as an argument(command line) d,e,f are going to be size of arrays(which are a part of a structure) typedef struct { blah blah } ex; ex ex0[d]; I am very confused about how to pass all these as argument. Right now I have hard coded these values,which apparently I should not be doing.

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  • passing array of structs from c# to regular dll

    - by buzz
    Hi there I have a regular dll with the followign fucntion exported. extern "C" __declspec(dllexport) int FindNearestStuff(double _latitude, double _longitude , LocationStruct * locations[]) LocationStruct is very simple struct LocationStruct { long positionIndex; long item; }; I'm tryign to call it from c# using [DllImport("myclever.dll", CharSet = CharSet.None)] private static extern int FindNearestStuff(double _latitude, double _longitude, ref LocationStruct [] locations); Its all cool and funky and i can step into the dll function from the debugger. Inside the dll the LocationStruct array is populated correctly and all is very good. the problem i have is when it returns back from the dll, the LocationStruct array is not coming back with the data - just empty values... what am i missing? cheers Buzz

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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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