Here’s an option: #include <iostream> #include <type_traits> #include <string> template <class, template <class> class> struct is_instance : public std::false_type {}; template <class T, template <class> class U> struct is_instance<U<T>, U> : public std::true_type {}; template <class> class Second {}; int main() { using A = Second<int>; using B = Second<std::string>; using C = float; std::cout … Read more
Update your AppServiceProvider by adding a view composer to the boot method and using ‘*’ to share it with all views: <?php namespace App\Providers; use Illuminate\Support\ServiceProvider; class AppServiceProvider extends ServiceProvider { /** * Bootstrap any application services. * * @return void */ public function boot() { view()->composer(‘*’, function($view){ $view_name = str_replace(‘.’, ‘-‘, $view->getName()); view()->share(‘view_name’, $view_name); … Read more
I was looking for the same answer, so figured I’d share my solution here. I wanted to override the default url template tag in django without having to use a custom template tag and load it in every template file. The goal was to replace %20 (spaces) with + (pluses). Here’s what I came up … Read more
This can be done in C++11 using variadic templates. Continuing from Pete’s answer: // Visitor template declaration template<typename… Types> class Visitor; // specialization for single type template<typename T> class Visitor<T> { public: virtual void visit(T & visitable) = 0; }; // specialization for multiple types template<typename T, typename… Types> class Visitor<T, Types…> : public Visitor<Types…> … Read more
This article describes a neat trick: http://www.gotw.ca/publications/mxc++-item-4.htm Here’s the basic idea. You first need an IsDerivedFrom class (this provides runtime and compile-time checking): template<typename D, typename B> class IsDerivedFrom { class No { }; class Yes { No no[3]; }; static Yes Test( B* ); // not defined static No Test( … ); // not … Read more
You won’t need dependency properties because you are inheriting from Button. You already have the IsPressed and IsEnabled properties. In fact, this is all you need: <Button x:Class=”TestWpfApplication.ThreeStateImageButton” xmlns=”http://schemas.microsoft.com/winfx/2006/xaml/presentation” xmlns:x=”http://schemas.microsoft.com/winfx/2006/xaml”> <Button.Template> <ControlTemplate TargetType=”{x:Type Button}”> <Grid> <Image Name=”Normal” Source=”Resources/Normal.png”/> <Image Name=”Pressed” Source=”Resources/Pressed.png” Visibility=”Hidden”/> <Image Name=”Disabled” Source=”Resources/Disabled.png” Visibility=”Hidden”/> </Grid> <ControlTemplate.Triggers> <Trigger Property=”IsPressed” Value=”True”> <Setter TargetName=”Normal” Property=”Visibility” Value=”Hidden”/> … Read more
While leaving it blank is the obvious option, I’d go with #define conditional_noop(x) do {} while(0) This trick is obviously no-op, but forces you to write a semicolon after conditional_noop(123).
Traits solution. Generalize not more than needed, and not less. In some cases that solution might not be enough as it will match any template with such signature (e.g. shared_ptr), in which case you could make use of type_traits, very much like duck-typing (templates are duck typed in general). #include <type_traits> // Helper to determine … Read more
You could use typeid: if (typeid(T) == typeid(int)) Or you could use the std::is_same type trait: if (std::is_same<T, int>::value)
In list<tNode<T>*>::iterator, you have a dependant name, that is, a name that depends on a template parameter. As such, the compiler can’t inspect list<tNode<T>*> (it doesn’t have its definition at this point) and so it doesn’t know whether list<tNode<T>*>::iterator is either a static field or a type. In such a situation, the compiler assumes that … Read more