ClickHouse/base/poco/Foundation/include/Poco/MetaProgramming.h

//
// MetaProgramming.h
//
// Library: Foundation
// Package: Core
// Module:  MetaProgramming
//
// Common definitions useful for Meta Template Programming
//
// Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier:	BSL-1.0
//


#ifndef Foundation_MetaProgramming_INCLUDED
#define Foundation_MetaProgramming_INCLUDED


#include "Poco/Foundation.h"


namespace Poco
{


template <typename T>
struct IsReference
/// Use this struct to determine if a template type is a reference.
{
    enum
    {
        VALUE = 0
    };
};


template <typename T>
struct IsReference<T &>
{
    enum
    {
        VALUE = 1
    };
};


template <typename T>
struct IsReference<const T &>
{
    enum
    {
        VALUE = 1
    };
};


template <typename T>
struct IsConst
/// Use this struct to determine if a template type is a const type.
{
    enum
    {
        VALUE = 0
    };
};


template <typename T>
struct IsConst<const T &>
{
    enum
    {
        VALUE = 1
    };
};


template <typename T>
struct IsConst<const T>
{
    enum
    {
        VALUE = 1
    };
};


template <typename T, int i>
struct IsConst<const T[i]>
/// Specialization for const char arrays
{
    enum
    {
        VALUE = 1
    };
};


template <typename T>
struct TypeWrapper
/// Use the type wrapper if you want to decouple constness and references from template types.
{
    typedef T TYPE;
    typedef const T CONSTTYPE;
    typedef T & REFTYPE;
    typedef const T & CONSTREFTYPE;
};


template <typename T>
struct TypeWrapper<const T>
{
    typedef T TYPE;
    typedef const T CONSTTYPE;
    typedef T & REFTYPE;
    typedef const T & CONSTREFTYPE;
};


template <typename T>
struct TypeWrapper<const T &>
{
    typedef T TYPE;
    typedef const T CONSTTYPE;
    typedef T & REFTYPE;
    typedef const T & CONSTREFTYPE;
};


template <typename T>
struct TypeWrapper<T &>
{
    typedef T TYPE;
    typedef const T CONSTTYPE;
    typedef T & REFTYPE;
    typedef const T & CONSTREFTYPE;
};


} // namespace Poco


#endif // Foundation_MetaProgramming_INCLUDED