Dune::Std::to_false_type< T > Class Template Reference

template mapping a type to std::false_type More...

#include <dune/common/std/type_traits.hh>

Detailed Description

template<typename T>
class Dune::Std::to_false_type< T >

template mapping a type to std::false_type

Template Parameters

T

Some type

Suppose you have a template class. You want to document the required members of this class in the non-specialized template, but you know that actually instantiating the non-specialized template is an error. You can try something like this:

template<typename T>
struct Traits
{
  static_assert(false,
                "Instanciating this non-specialized template is an "
                "error. You should use one of the specializations "
                "instead.");
  typedef void FrobnicateType;
};

This will trigger static_assert() as soon as the compiler reads the definition for the Traits template, since it knows that "false" can never become true, no matter what the template parameters of Traits are. As a workaround you can use to_false_type: replace false by to_false_type<T>::value, like this:

template<typename T>
struct Traits
{
  static_assert(Std::to_false_type<T>::value,
                "Instanciating this non-specialized template is an "
                "error. You should use one of the specializations "
                "instead.");
  typedef void FrobnicateType;
};

Since there might be an specialization of to_false_type for template parameter T, the compiler cannot trigger static_assert() until the type of T is known, that is, until Traits<T> is instantiated.

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The documentation for this class was generated from the following file:

• dune/common/std/type_traits.hh