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  • how to write a constructor...

    - by Nima
    is that correct to write a constructor like this? class A { A::A(const A& a) { .... } }; if yes, then is it correct to invoke it like this: A* other; ... A* instance = new A(*(other)); if not, what do you suggest? Thanks

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  • Function with parameter type that has a copy-constructor with non-const ref chosen?

    - by Johannes Schaub - litb
    Some time ago I was confused by the following behavior of some code when I wanted to write a is_callable<F, Args...> trait. Overload resolution won't call functions accepting arguments by non-const ref, right? Why doesn't it reject in the following because the constructor wants a Test&? I expected it to take f(int)! struct Test { Test() { } // I want Test not be copyable from rvalues! Test(Test&) { } // But it's convertible to int operator int() { return 0; } }; void f(int) { } void f(Test) { } struct WorksFine { }; struct Slurper { Slurper(WorksFine&) { } }; struct Eater { Eater(WorksFine) { } }; void g(Slurper) { } void g(Eater) { } // chooses this, as expected int main() { // Error, why? f(Test()); // But this works, why? g(WorksFine()); } Error message is m.cpp: In function 'int main()': m.cpp:33:11: error: no matching function for call to 'Test::Test(Test)' m.cpp:5:3: note: candidates are: Test::Test(Test&) m.cpp:2:3: note: Test::Test() m.cpp:33:11: error: initializing argument 1 of 'void f(Test)' Can you please explain why one works but the other doesn't?

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  • Delphi constants and references

    - by Sambatyon
    I want to pass constant references to functions in delphi, so I am sure that the referenced object won't change and to save time and memory. So I want to declare a function like function foo(var const Value : Bar) : Boolean; however this is not allowed. I thought constant values would be automatically sent as references. However I found out that it is not the case (getting the address of an object before sending it to the function gives me $12F50C and the address of the same object inside the function is $12F564) What can I do to send constant references?

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  • Sharing common class in wcf project

    - by Saint
    class MyCommonClass { //properties } This class should be accessible in service project wcf-client project the other for which they are references. In this common project I can't generate servicereferences. I think, I could don't generate MyCommonClass in ServiceReferences but how to mark class to be nonserializable? In properties there's IgnoreDataMemberAttribute. I tried also reuse MyCommonClass type located in common project, but it is still generated

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  • "Home" of Javascript similar to python.org?

    - by drewk
    Perl, Ruby, Python, Javascript / ecmascript, PHP are all similar in the sense of being open source, open documentation, multi-platform, etc. Perl has http://www.perl.org Ruby has http://www.ruby-lang.org Python has http://www.python.org PHP has http://php.net Is there a "home" for javascript in the same sense as these other languages? When I say "home" I mean the go-to place for official documentation, specifications, source code of the language, examples, etc.

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  • Is there any way to add references without recompiling in .NET?

    - by Jader Dias
    I am using a IoC Container (Castle Windsor) to instantiate classes accordingly to the configuration file. If I want to add classes from a new dll that didn't exist when I compiled the project, there is any way to do that without recompiling? Edit: As this project is a Service Host for WCF service, and the classes that I want to include after compilation are WCF Services I would like also to know if I can include endpoint information about new services without recompiling.

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  • Output is different for R-value and L-value. Why?

    - by Leonid Volnitsky
    Can someone explain to me why output for R-value is different from L-value? #include <iostream> #include <vector> using namespace std; template<typename Ct> struct ct_wrapper { Ct&& ct; // R or L ref explicit ct_wrapper(Ct&& ct) : ct(std::forward<Ct>(ct)) { std::cout << this->ct[1];}; }; int main() { // L-val vector<int> v{1,2,3}; ct_wrapper<vector<int>&> lv(v); cout << endl << lv.ct[0] << lv.ct[1] << lv.ct[2] << endl; // R-val ct_wrapper<vector<int>&&> rv(vector<int>{1,2,3}); cout << endl << rv.ct[0] << rv.ct[1] << rv.ct[2] << endl; } Output (same for gcc48 and clang32): 2 123 2 003

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  • app.config files of referenced dlls

    - by ban-dana
    I have a Web Project (VS 2008) that references a bunch of DLLs. The DLLs are built separately, so the project references binaries and not DLL projects. Some of the DLLs have their own app.config, which I want to be copied autmatically to the web project's output directory. Is there any suitable generic way to achieve this?

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  • What's a reasonable way to mutate a primitive variable from an anonymous Java class?

    - by Steve
    I would like to write the following code: boolean found = false; search(new SearchCallback() { @Override void onFound(Object o) { found = true; } }); Obviously this is not allowed, since found needs to be final. I can't make found a member field for thread-safety reasons. What is the best alternative? One workaround is to define final class MutableReference<T> { private T value; MutableReference(T value) { this.value = value; } T get() { return value; } void set(T value) { this.value = value; } } but this ends up taking a lot of space when formatted properly, and I'd rather not reinvent the wheel if at all possible. I could use a List<Boolean> with a single element (either mutating that element, or else emptying the list) or even a Boolean[1]. But everything seems to smell funny, since none of the options are being used as they were intended. What is a reasonable way to do this?

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  • Assigning a variable of a struct that contains an instance of a class to another variable

    - by xport
    In my understanding, assigning a variable of a struct to another variable of the same type will make a copy. But this rule seems broken as shown on the following figure. Could you explain why this happened? using System; namespace ReferenceInValue { class Inner { public int data; public Inner(int data) { this.data = data; } } struct Outer { public Inner inner; public Outer(int data) { this.inner = new Inner(data); } } class Program { static void Main(string[] args) { Outer p1 = new Outer(1); Outer p2 = p1; Console.WriteLine("p1:{0}, p2:{1}", p1.inner.data, p2.inner.data); p1.inner.data = 2; Console.WriteLine("p1:{0}, p2:{1}", p1.inner.data, p2.inner.data); p2.inner.data = 3; Console.WriteLine("p1:{0}, p2:{1}", p1.inner.data, p2.inner.data); Console.ReadKey(); } } }

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  • Returning a local object from a function

    - by pocoa
    Is this the right way to return an object from a function? Car getCar(string model, int year) { Car c(model, year); return c; } void displayCar(Car &car) { cout << car.getModel() << ", " << car.getYear() << endl; } displayCar(getCar("Honda", 1999)); I'm getting an error, "taking address of temporary". Should I use this way: Car &getCar(string model, int year) { Car c(model, year); return c; }

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  • Custom string class (C++)

    - by Sanctus2099
    Hey guys. I'm trying to write my own C++ String class for educational and need purposes. The first thing is that I don't know that much about operators and that's why I want to learn them. I started writing my class but when I run it it blocks the program but does not do any crash. Take a look at the following code please before reading further: class CString { private: char* cstr; public: CString(); CString(char* str); CString(CString& str); ~CString(); operator char*(); operator const char*(); CString operator+(const CString& q)const; CString operator=(const CString& q); }; First of all I'm not so sure I declared everything right. I tried googleing about it but all the tutorials about overloading explain the basic ideea which is very simple but lack to explain how and when each thing is called. For instance in my = operator the program calls CString(CString& str); but I have no ideea why. I have also attached the cpp file below: CString::CString() { cstr=0; } CString::CString(char *str) { cstr=new char[strlen(str)]; strcpy(cstr,str); } CString::CString(CString& q) { if(this==&q) return; cstr = new char[strlen(q.cstr)+1]; strcpy(cstr,q.cstr); } CString::~CString() { if(cstr) delete[] cstr; } CString::operator char*() { return cstr; } CString::operator const char* () { return cstr; } CString CString::operator +(const CString &q) const { CString s; s.cstr = new char[strlen(cstr)+strlen(q.cstr)+1]; strcpy(s.cstr,cstr); strcat(s.cstr,q.cstr); return s; } CString CString::operator =(const CString &q) { if(this!=&q) { if(cstr) delete[] cstr; cstr = new char[strlen(q.cstr)+1]; strcpy(cstr,q.cstr); } return *this; } For testing I used a code just as simple as this CString a = CString("Hello") + CString(" World"); printf(a); I tried debugging it but at a point I get lost. First it calls the constructor 2 times for "hello" and for " world". Then it get's in the + operator which is fine. Then it calls the constructor for the empty string. After that it get's into "CString(CString& str)" and now I'm lost. Why is this happening? After this I noticed my string containing "Hello World" is in the destructor (a few times in a row). Again I'm very puzzeled. After converting again from char* to Cstring and back and forth it stops. It never get's into the = operator but neither does it go further. printf(a) is never reached. I use VisualStudio 2010 for this but it's basically just standard c++ code and thus I don't think it should make that much of a difference

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  • How to add .Net3.5 dll into .Net2.0 project?

    - by macias
    I have a dll which is based on .net 3.5 -- it uses internally for example Linq, but the exposed API is straightforward, no fancy stuff. Since C# generics are resolved at compile time I assume that for calling party all it counts is API (all public parts). However when I try to use this dll from net2.0 project I get info, that the dll cannot be referenced because the dll or one of its dependencies requires a later version of .net framework. I can install any .net version I want on target computer (when entire app is installed), but I cannot change .net version for the project itself. So: how to solve this? When adding a C dll to this project I had no such problems, so are C# dlls self-contained or not?

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  • Most efficient way of checking for a return from a function call in Perl

    - by Gaurav Dadhania
    I want to add the return value from the function call to an array iff something is returned (not by default, i.e. if I have a return statement in the subroutine.) so I'm using unshift @{$errors}, "HashValidator::$vfunction($hashref)"; but this actually adds the string of the function call to the array. I also tried unshift @{$errors}, $temp if defined my $temp = "HashValidator::$vfunction($hashref)"; with the same result. What would a perl one-liner look like that does this efficiently (I know I can do the ugly, multi-line check but I want to learn). Thanks,

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  • Symfony Form render with Self Referenced Entity

    - by benarth
    I have an Entity containing Self-Referenced mapping. class Category { /** * @var integer * * @ORM\Column(name="id", type="integer") * @ORM\Id * @ORM\GeneratedValue(strategy="AUTO") */ private $id; /** * @var string * * @ORM\Column(name="name", type="string", length=100) */ private $name; /** * @ORM\OneToMany(targetEntity="Category", mappedBy="parent") */ private $children; /** * @ORM\ManyToOne(targetEntity="Category", inversedBy="children") * @ORM\JoinColumn(name="parent_id", referencedColumnName="id") */ private $parent; } In my CategoryType I have this : public function buildForm(FormBuilderInterface $builder, array $options) { $plan = $this->plan; $builder->add('name'); $builder->add('parent', 'entity', array( 'class' => 'xxxBundle:Category', 'property' => 'name', 'empty_value' => 'Choose a parent category', 'required' => false, 'query_builder' => function(EntityRepository $er) use ($plan) { return $er->createQueryBuilder('u') ->where('u.plan = :plan') ->setParameter('plan', $plan) ->orderBy('u.id', 'ASC'); }, )); } Actually, when I render the form field Category this is something like Cat1 Cat2 Cat3 Subcat1 Subcat2 Cat4 I would like to know if it's possible and how to display something more like, a kind of a simple tree representation : Cat1 Cat2 Cat3 -- Subcat1 -- Subcat2 Cat4 Regards.

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  • How do I add a VSTO project as a reference to a unit testing project?

    - by Mathias
    In order not to pollute my projects with unit tests, I like to create a separate project for my unit tests; I add a reference to the project under test in the unit tests project. However, this isn't working that well with my VSTO excel add-in projects: when I create a separate unit test project and go to Add Reference Projects, there is no project to pick. What I have done so far is Add Reference Browse, and pick the add-in dll from the debug folder. I have also run into issues from time to time with this, with the reference suddenly not working, requiring to remove/re-add the dll reference. Can anybody explain why a VSTO project doesn't show up as a regular project? And is there a better way to go about it than what I am doing presently?

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  • C++ Implicit Conversion Operators

    - by Imbue
    I'm trying to find a nice inheritance solution in C++. I have a Rectangle class and a Square class. The Square class can't publicly inherit from Rectangle, because it cannot completely fulfill the rectangle's requirements. For example, a Rectangle can have it's width and height each set separately, and this of course is impossible with a Square. So, my dilemma. Square obviously will share a lot of code with Rectangle; they are quite similar. For examlpe, if I have a function like: bool IsPointInRectangle(const Rectangle& rect); it should work for a square too. In fact, I have a ton of such functions. So in making my Square class, I figured I would use private inheritance with a publicly accessible Rectangle conversion operator. So my square class looks like: class Square : private Rectangle { public: operator const Rectangle&() const; }; However, when I try to pass a Square to the IsPointInRectangle function, my compiler just complains that "Rectangle is an inaccessible base" in that context. I expect it to notice the Rectangle operator and use that instead. Is what I'm trying to do even possible? If this can't work I'm probably going to refactor part of Rectangle into MutableRectangle class. Thanks.

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  • How do I call a function name that is stored in a hash in Perl?

    - by Ether
    I'm sure this is covered in the documentation somewhere but I have been unable to find it... I'm looking for the syntactic sugar that will make it possible to call a method on a class whose name is stored in a hash (as opposed to a simple scalar): use strict; use warnings; package Foo; sub foo { print "in foo()\n" } package main; my %hash = (func => 'foo'); Foo->$hash{func}; If I copy $hash{func} into a scalar variable first, then I can call Foo->$func just fine... but what is missing to enable Foo->$hash{func} to work? (EDIT: I don't mean to do anything special by calling a method on class Foo -- this could just as easily be a blessed object (and in my actual code it is); it was just easier to write up a self-contained example using a class method.) EDIT 2: Just for completeness re the comments below, this is what I'm actually doing (this is in a library of Moose attribute sugar, created with Moose::Exporter): # adds an accessor to a sibling module sub foreignTable { my ($meta, $table, %args) = @_; my $class = 'MyApp::Dir1::Dir2::' . $table; my $dbAccessor = lcfirst $table; eval "require $class" or do { die "Can't load $class: $@" }; $meta->add_attribute( $table, is => 'ro', isa => $class, init_arg => undef, # don't allow in constructor lazy => 1, predicate => 'has_' . $table, default => sub { my $this = shift; $this->debug("in builder for $class"); ### here's the line that uses a hash value as the method name my @args = ($args{primaryKey} => $this->${\$args{primaryKey}}); push @args, ( _dbObject => $this->_dbObject->$dbAccessor ) if $args{fkRelationshipExists}; $this->debug("passing these values to $class -> new: @args"); $class->new(@args); }, ); } I've replaced the marked line above with this: my $pk_accessor = $this->meta->find_attribute_by_name($args{primaryKey})->get_read_method_ref; my @args = ($args{primaryKey} => $this->$pk_accessor); PS. I've just noticed that this same technique (using the Moose meta class to look up the coderef rather than assuming its naming convention) cannot also be used for predicates, as Class::MOP::Attribute does not have a similar get_predicate_method_ref accessor. :(

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  • Does a simple delphi form app needs any libraries or dependencies to deploy?

    - by peterg
    I need to code a simple form application and I want to make it easy to deploy (without installing libraries or dependencies), I don't want to use visual studio cpp or csharp because clr apps compile with .net frameworks and I have no much experience with mfc and dialogs. So I was wondering which libraries does a simple delphi vcl forms app (those using TForm) use, because I've never had to install anything to run simple delphi apps.

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  • Difference of function argument as (const int &) and (int & a) in C++

    - by Narek
    I know that if you write void function_name(int& a), then function will not do local copy of your variable passed as argument. Also have met in literature that you should write void function_name(const int & a) in order to say compiler, that I dont want the variable passed as argument to be copied. So my question: what is the difference with this two cases (except that "const" enshures that the variable passes will not be changed by function!!!)???

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