74 lines
2.0 KiB
C++
74 lines
2.0 KiB
C++
/////////////////////////////////////////////////////////////////////////////
|
|
// Name: wx/meta/if.h
|
|
// Purpose: declares wxIf<> metaprogramming construct
|
|
// Author: Vaclav Slavik
|
|
// Created: 2008-01-22
|
|
// RCS-ID: $Id: if.h 61724 2009-08-21 10:41:26Z VZ $
|
|
// Copyright: (c) 2008 Vaclav Slavik
|
|
// Licence: wxWindows licence
|
|
/////////////////////////////////////////////////////////////////////////////
|
|
|
|
#ifndef _WX_META_IF_H_
|
|
#define _WX_META_IF_H_
|
|
|
|
#include "wx/defs.h"
|
|
|
|
// NB: This code is intentionally written without partial templates
|
|
// specialization, because some older compilers (notably VC6) don't
|
|
// support it.
|
|
|
|
namespace wxPrivate
|
|
{
|
|
|
|
template <bool Cond>
|
|
struct wxIfImpl
|
|
|
|
// broken VC6 needs not just an incomplete template class declaration but a
|
|
// "skeleton" declaration of the specialized versions below as it apparently
|
|
// tries to look up the types in the generic template definition at some moment
|
|
// even though it ends up by using the correct specialization in the end -- but
|
|
// without this skeleton it doesn't recognize Result as a class at all below
|
|
#if defined(__VISUALC__) && !wxCHECK_VISUALC_VERSION(7)
|
|
{
|
|
template<typename TTrue, typename TFalse> struct Result {};
|
|
}
|
|
#endif // VC++ <= 6
|
|
;
|
|
|
|
// specialization for true:
|
|
template <>
|
|
struct wxIfImpl<true>
|
|
{
|
|
template<typename TTrue, typename TFalse> struct Result
|
|
{
|
|
typedef TTrue value;
|
|
};
|
|
};
|
|
|
|
// specialization for false:
|
|
template<>
|
|
struct wxIfImpl<false>
|
|
{
|
|
template<typename TTrue, typename TFalse> struct Result
|
|
{
|
|
typedef TFalse value;
|
|
};
|
|
};
|
|
|
|
} // namespace wxPrivate
|
|
|
|
// wxIf<> template defines nested type "value" which is the same as
|
|
// TTrue if the condition Cond (boolean compile-time constant) was met and
|
|
// TFalse if it wasn't.
|
|
//
|
|
// See wxVector<T> in vector.h for usage example
|
|
template<bool Cond, typename TTrue, typename TFalse>
|
|
struct wxIf
|
|
{
|
|
typedef typename wxPrivate::wxIfImpl<Cond>
|
|
::template Result<TTrue, TFalse>::value
|
|
value;
|
|
};
|
|
|
|
#endif // _WX_META_IF_H_
|