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////////////////////////////////////////////////////////////////////////////////
// The Loki Library
// Copyright (c) 2001 by Andrei Alexandrescu
// This code accompanies the book:
// Alexandrescu, Andrei. "Modern C++ Design: Generic Programming and Design
// Patterns Applied". Copyright (c) 2001. Addison-Wesley.
// Permission to use, copy, modify, distribute and sell this software for any
// purpose is hereby granted without fee, provided that the above copyright
// notice appear in all copies and that both that copyright notice and this
// permission notice appear in supporting documentation.
// The author or Addison-Welsey Longman make no representations about the
// suitability of this software for any purpose. It is provided "as is"
// without express or implied warranty.
////////////////////////////////////////////////////////////////////////////////
// Last update: November 22, 2001
#ifndef TYPEMANIP_INC_
#define TYPEMANIP_INC_
namespace Loki
{
////////////////////////////////////////////////////////////////////////////////
// class template Int2Type
// Converts each integral constant into a unique type
// Invocation: Int2Type<v> where v is a compile-time constant integral
// Defines 'value', an enum that evaluates to v
////////////////////////////////////////////////////////////////////////////////
template <int v>
struct Int2Type
{
enum { value = v };
};
////////////////////////////////////////////////////////////////////////////////
// class template Type2Type
// Converts each type into a unique, insipid type
// Invocation Type2Type<T> where T is a type
// Defines the type OriginalType which maps back to T
////////////////////////////////////////////////////////////////////////////////
template <typename T>
struct Type2Type
{
typedef T OriginalType;
};
////////////////////////////////////////////////////////////////////////////////
// class template Select
// Selects one of two types based upon a boolean constant
// Invocation: Select<flag, T, U>::Result
// where:
// flag is a compile-time boolean constant
// T and U are types
// Result evaluates to T if flag is true, and to U otherwise.
////////////////////////////////////////////////////////////////////////////////
template <bool flag, typename T, typename U>
struct Select
{
typedef T Result;
};
template <typename T, typename U>
struct Select<false, T, U>
{
typedef U Result;
};
////////////////////////////////////////////////////////////////////////////////
// class template IsSameType
// Return true iff two given types are the same
// Invocation: SameType<T, U>::value
// where:
// T and U are types
// Result evaluates to true iff U == T (types equal)
////////////////////////////////////////////////////////////////////////////////
template <typename T, typename U>
struct IsSameType
{
enum { value = false };
};
template <typename T>
struct IsSameType<T,T>
{
enum { value = true };
};
////////////////////////////////////////////////////////////////////////////////
// Helper types Small and Big - guarantee that sizeof(Small) < sizeof(Big)
////////////////////////////////////////////////////////////////////////////////
namespace Private
{
template <class T, class U>
struct ConversionHelper
{
typedef char Small;
struct Big { char dummy[2]; };
static Big Test(...);
static Small Test(U);
static T MakeT();
};
}
////////////////////////////////////////////////////////////////////////////////
// class template Conversion
// Figures out the conversion relationships between two types
// Invocations (T and U are types):
// a) Conversion<T, U>::exists
// returns (at compile time) true if there is an implicit conversion from T
// to U (example: Derived to Base)
// b) Conversion<T, U>::exists2Way
// returns (at compile time) true if there are both conversions from T
// to U and from U to T (example: int to char and back)
// c) Conversion<T, U>::sameType
// returns (at compile time) true if T and U represent the same type
//
// Caveat: might not work if T and U are in a private inheritance hierarchy.
////////////////////////////////////////////////////////////////////////////////
template <class T, class U>
struct Conversion
{
typedef Private::ConversionHelper<T, U> H;
#ifndef __MWERKS__
enum { exists = sizeof(typename H::Small) == sizeof((H::Test(H::MakeT()))) };
#else
enum { exists = false };
#endif
enum { exists2Way = exists && Conversion<U, T>::exists };
enum { sameType = false };
};
template <class T>
struct Conversion<T, T>
{
enum { exists = 1, exists2Way = 1, sameType = 1 };
};
template <class T>
struct Conversion<void, T>
{
enum { exists = 0, exists2Way = 0, sameType = 0 };
};
template <class T>
struct Conversion<T, void>
{
enum { exists = 0, exists2Way = 0, sameType = 0 };
};
template <>
struct Conversion<void, void>
{
public:
enum { exists = 1, exists2Way = 1, sameType = 1 };
};
////////////////////////////////////////////////////////////////////////////////
// class template SuperSubclass
// Invocation: SuperSubclass<B, D>::value where B and D are types.
// Returns true if B is a public base of D, or if B and D are aliases of the
// same type.
//
// Caveat: might not work if T and U are in a private inheritance hierarchy.
////////////////////////////////////////////////////////////////////////////////
template <class T, class U>
struct SuperSubclass
{
enum { value = (::Loki::Conversion<const volatile U*, const volatile T*>::exists &&
!::Loki::Conversion<const volatile T*, const volatile void*>::sameType) };
};
////////////////////////////////////////////////////////////////////////////////
// class template SuperSubclassStrict
// Invocation: SuperSubclassStrict<B, D>::value where B and D are types.
// Returns true if B is a public base of D.
//
// Caveat: might not work if T and U are in a private inheritance hierarchy.
////////////////////////////////////////////////////////////////////////////////
template<class T,class U>
struct SuperSubclassStrict
{
enum { value = (::Loki::Conversion<const volatile U*, const volatile T*>::exists &&
!::Loki::Conversion<const volatile T*, const volatile void*>::sameType &&
!::Loki::Conversion<const volatile T*, const volatile U*>::sameType) };
};
} // namespace Loki
////////////////////////////////////////////////////////////////////////////////
// macro SUPERSUBCLASS
// Invocation: SUPERSUBCLASS(B, D) where B and D are types.
// Returns true if B is a public base of D, or if B and D are aliases of the
// same type.
//
// Caveat: might not work if T and U are in a private inheritance hierarchy.
// Deprecated: Use SuperSubclass class template instead.
////////////////////////////////////////////////////////////////////////////////
#define SUPERSUBCLASS(T, U) \
::Loki::SuperSubclass<T,U>::value
////////////////////////////////////////////////////////////////////////////////
// macro SUPERSUBCLASS_STRICT
// Invocation: SUPERSUBCLASS(B, D) where B and D are types.
// Returns true if B is a public base of D.
//
// Caveat: might not work if T and U are in a private inheritance hierarchy.
// Deprecated: Use SuperSubclassStrict class template instead.
////////////////////////////////////////////////////////////////////////////////
#define SUPERSUBCLASS_STRICT(T, U) \
::Loki::SuperSubclassStrict<T,U>::value
////////////////////////////////////////////////////////////////////////////////
// Change log:
// June 20, 2001: ported by Nick Thurn to gcc 2.95.3. Kudos, Nick!!!
// November 22, 2001: minor change to support porting to boost
// November 22, 2001: fixed bug in Conversion<void, T>
// (credit due to Brad Town)
// November 23, 2001: (well it's 12:01 am) fixed bug in SUPERSUBCLASS - added
// the volatile qualifier to be 100% politically correct
// September 16, 2002: Changed "const volatile" to "const volatile *", to enable
// conversion to succeed. Done earlier by MKH.
// Added SuperSubclass and SuperSubclassStrict templates. The corresponding
// macros are deprecated.
// Added extra parenthesis in sizeof in Conversion, to disambiguate function
// call from function declaration. T.S.
////////////////////////////////////////////////////////////////////////////////
#endif // TYPEMANIP_INC_
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