Parma_Polyhedra_Library::Is_Same_Or_Derived< Base, Derived > Struct Template Reference

A class holding a constant called value that evaluates to true if and only if Base is the same type as Derived or Derived is a class derived from Base. More...

#include <meta_programming.hh>

Inheritance diagram for Parma_Polyhedra_Library::Is_Same_Or_Derived< Base, Derived >:

List of all members.

Classes
struct	Any
	A class that is constructible from just anything. More...
Public Types
enum	const_bool_value { value = (sizeof(func(derived_object())) == sizeof(char)) }
Public Member Functions
	PPL_COMPILE_TIME_CHECK (sizeof(char)!=sizeof(double),"architecture with sizeof(char) == sizeof(double)"" (!?)")
Static Public Member Functions
static char	func (const Base &)
	Overloading with Base.
static double	func (Any)
	Overloading with Any.
static const Derived &	derived_object ()
	A function obtaining a const reference to a Derived object.

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Detailed Description

template<typename Base, typename Derived>
struct Parma_Polyhedra_Library::Is_Same_Or_Derived< Base, Derived >

A class holding a constant called value that evaluates to true if and only if Base is the same type as Derived or Derived is a class derived from Base.

Note:

Care must be taken to use this predicate with template classes. Suppose we have

  template <typename T> struct B;
  template <typename T> struct D : public B<T>;

Of course, we cannot test if, for some type variable U, we have Is_Same_Or_Derived<B<U>, Type>:: const_bool_value:: value == true. But we can do as follows:

  struct B_Base {
  };

  template <typename T> struct B : public B_Base;

This enables us to inquire Is_Same_Or_Derived<B_Base, Type>:: const_bool_value:: value.

Definition at line 223 of file meta_programming.hh.

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Member Enumeration Documentation

template<typename Base, typename Derived>

enum Parma_Polyhedra_Library::Is_Same_Or_Derived::const_bool_value

Enumerator:

value

Assuming sizeof(char) != sizeof(double), the C++ overload resolution mechanism guarantees that value evaluates to true if and only if Base is the same type as Derived or Derived is a class derived from Base.

Definition at line 247 of file meta_programming.hh.

                        {
    value = (sizeof(func(derived_object())) == sizeof(char))
  };

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Member Function Documentation

template<typename Base, typename Derived>

static const Derived& Parma_Polyhedra_Library::Is_Same_Or_Derived< Base, Derived >::derived_object ( )

static

A function obtaining a const reference to a Derived object.

template<typename Base, typename Derived>

static char Parma_Polyhedra_Library::Is_Same_Or_Derived< Base, Derived >::func ( const Base &  )

static

Overloading with Base.

template<typename Base, typename Derived>

static double Parma_Polyhedra_Library::Is_Same_Or_Derived< Base, Derived >::func ( Any  )

static

Overloading with Any.

template<typename Base, typename Derived>

Parma_Polyhedra_Library::Is_Same_Or_Derived< Base, Derived >::PPL_COMPILE_TIME_CHECK

(

sizeof(char)!

= sizeof(double)

)

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

• meta_programming.hh