callback_common.h

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/** @file
 *  @author Bram de Greve (bram@cocamware.com)
 *  @author Tom De Muer (tom@cocamware.com)
 *
 *  *** BEGIN LICENSE INFORMATION ***
 *  
 *  The contents of this file are subject to the Common Public Attribution License 
 *  Version 1.0 (the "License"); you may not use this file except in compliance with 
 *  the License. You may obtain a copy of the License at 
 *  http://lass.sourceforge.net/cpal-license. The License is based on the 
 *  Mozilla Public License Version 1.1 but Sections 14 and 15 have been added to cover 
 *  use of software over a computer network and provide for limited attribution for 
 *  the Original Developer. In addition, Exhibit A has been modified to be consistent 
 *  with Exhibit B.
 *  
 *  Software distributed under the License is distributed on an "AS IS" basis, WITHOUT 
 *  WARRANTY OF ANY KIND, either express or implied. See the License for the specific 
 *  language governing rights and limitations under the License.
 *  
 *  The Original Code is LASS - Library of Assembled Shared Sources.
 *  
 *  The Initial Developer of the Original Code is Bram de Greve and Tom De Muer.
 *  The Original Developer is the Initial Developer.
 *  
 *  All portions of the code written by the Initial Developer are:
 *  Copyright (C) 2004-2025 the Initial Developer.
 *  All Rights Reserved.
 *  
 *  Contributor(s):
 *
 *  Alternatively, the contents of this file may be used under the terms of the 
 *  GNU General Public License Version 2 or later (the GPL), in which case the 
 *  provisions of GPL are applicable instead of those above.  If you wish to allow use
 *  of your version of this file only under the terms of the GPL and not to allow 
 *  others to use your version of this file under the CPAL, indicate your decision by 
 *  deleting the provisions above and replace them with the notice and other 
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 *  a recipient may use your version of this file under either the CPAL or the GPL.
 *  
 *  *** END LICENSE INFORMATION ***
 */
 
#ifndef LASS_GUARDIAN_OF_INCLUSION_UTIL_CALLBACK_COMMON_H
#define LASS_GUARDIAN_OF_INCLUSION_UTIL_CALLBACK_COMMON_H
 
#include "util_common.h"
#include "../meta/enable_if.h"
 
namespace lass
{
namespace util
{
 
/** @ingroup Callback
 */
class EmptyCallback: public ExceptionMixin<EmptyCallback>
{
public:
    EmptyCallback(std::string msg, std::string loc): ExceptionMixin<EmptyCallback>(std::move(msg), std::move(loc)) {}
    ~EmptyCallback() noexcept {}
};
 
 
 
namespace impl
{
 
template <typename T, typename = void>
struct IsEqualityComparable: public meta::False {};
 
template <typename T>
struct IsEqualityComparable<T, std::void_t<decltype(std::declval<const T&>() == std::declval<const T&>())>>: public meta::True {};
 
}
 
#if !LASS_HAVE_LAMBDA_OPERATOR_NOT
 
// With C++11, lambdas can also be used as callables. But the MSVC compiler did not support
// the unary !operator. This was fixed in VS 2019 version 16.2.
// https://twitter.com/lunasorcery/status/1092870113374687232
// https ://developercommunity.visualstudio.com/t/msvc-rejects-valid-lambda-auto-assignment-which-gc/447025
 
namespace impl
{
 
template <typename T>
class HasOperatorNot {
    template <typename C> static meta::True test(char[!C()]);
    template <typename C> static meta::False test(...);
public:
    enum { value = sizeof(test<T>(0)) == sizeof(meta::True) };
};
 
}
 
#endif
 
}
}
 
#endif
 
// EOF