any_predicate.hpp

Go to the documentation of this file.

// any_predicate.hpp
/*
 *  Copyright (c) 2007 Leigh Johnston.
 *
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are
 *  met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *
 *     * Neither the name of Leigh Johnston nor the names of any
 *       other contributors to this software may be used to endorse or
 *       promote products derived from this software without specific prior
 *       written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 *  IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 *  THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 *  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 *  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 *  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 *  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 *  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
 
#pragma once
 
#include <neolib/neolib.hpp>
#include <stdexcept>
#include <typeinfo>
 
namespace neolib
{
    template <typename T>
    class any_predicate
    {
        // types
    public:
        typedef T value_type;
        struct bad_cast : public std::logic_error { bad_cast() : std::logic_error("neolib::any_predicate::bad_cast") {} };
        struct no_predicate : public std::logic_error { no_predicate() : std::logic_error("neolib::any_predicate::no_predicate") {} };
    private:
        class holder_base
        {
            // construction
        public:
            virtual ~holder_base() = default;
            // operations
        public:
            virtual bool operator()(const value_type& aLeft, const value_type& aRight) const = 0;
            template <typename T>
            operator const T&() const
            {
                if (typeid(T) != type()) 
                    throw bad_cast();
                return *static_cast<const T*>(ptr());
            }
            template <typename T>
            operator T&()
            {
                if (typeid(T) != type()) 
                    throw bad_cast();
                return *static_cast<T*>(ptr());
            }
            template <typename T>
            bool is() const { return typeid(T) == type(); }
            virtual holder_base* clone() const = 0;
            // implementation
        private:
            virtual const std::type_info& type() const = 0;
            virtual const void* ptr() const = 0;
            virtual void* ptr() = 0;
        };
        template <typename T>
        class holder : public holder_base
        {
            // construction
        public:
            holder(const T& aObject) : iObject(aObject) {}
            // implementation
        private:
            virtual bool operator()(const value_type& aLeft, const value_type& aRight) const { return iObject(aLeft, aRight); }
            virtual holder_base* clone() const { return new holder(iObject); }
            virtual const std::type_info& type() const { return typeid(T); }
            virtual const void* ptr() const { return &iObject; }
            virtual void* ptr() { return &iObject; }
            // attributes
        private:
            T iObject;
        };
        // construction
    public:
        any_predicate() : iHolder(nullptr) {}
        template <typename T>
        any_predicate(const T& aObject) : iHolder(new holder<T>(aObject)) {}
        any_predicate(const any_predicate& aOther) : iHolder(aOther.iHolder ? aOther.iHolder->clone() : nullptr) {}
        ~any_predicate() { destroy(); }
        any_predicate& operator=(const any_predicate& aOther) 
        { 
            destroy(); 
            if (aOther.iHolder) 
                iHolder = aOther.iHolder->clone(); 
            return *this;
        }
        // operations
    public:
        bool operator()(const value_type& aLeft, const value_type& aRight) const 
        {
            if (empty())
                throw no_predicate();
            return (*iHolder)(aLeft, aRight);
        }
        template <typename T>
        operator const T&() const { if (empty()) throw bad_cast(); return *iHolder; }
        template <typename T>
        operator T&() { if (empty()) throw bad_cast(); return *iHolder; }
        template <typename T>
        bool is() const { return iHolder && iHolder->is<T>(); }
        bool something() const { return iHolder != nullptr; }
        bool empty() const { return !something(); }
        void reset() { destroy(); }
        // implementation
    private:
        void destroy() { delete iHolder; iHolder = nullptr; }
        // attributes
    private:
        holder_base* iHolder;
    };
}