#ifndef BOOST_NUMERIC_CHECKED_RESULT
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#define BOOST_NUMERIC_CHECKED_RESULT
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// Copyright (c) 2012 Robert Ramey
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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// contains operations for doing checked aritmetic on NATIVE
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// C++ types.
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#include <cassert>
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#include <type_traits> // is_convertible
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#include "exception.hpp"
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namespace boost {
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namespace safe_numerics {
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template<typename R>
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struct checked_result {
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const safe_numerics_error m_e;
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const union {
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R m_r;
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char const * m_msg;
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};
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// don't permit construction without initial value;
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checked_result() = delete;
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// note: I implemented the following non-default copy and move
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// constructors because I thought I needed to do this in order
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// to make them constexpr. Turns out though that doing this creates
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// a syntax error because the assignment results in error due
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// to assignment "outside of object lifetime". I think this could
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// be addressed by replacing the anonymous union above with a
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// named union. This would create some syntax changes which would
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// ripple through some parts of th program. So for now, we'll just
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// rely on the default copy and move constructors.
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#if 0
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// copy constructor
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constexpr /*explicit*/ checked_result(const checked_result & r) noexpect :
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m_e(r.m_e)
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{
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if(safe_numerics_error::success == r.m_e)
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m_r = r.m_r;
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else
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m_msg = r.m_msg;
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}
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// move constructor
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constexpr /*explicit*/ checked_result(checked_result && r) noexcept :
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m_e(r.m_e)
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{
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if(safe_numerics_error::success == r.m_e)
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m_r = r.m_r;
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else
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m_msg = r.m_msg;
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}
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#endif
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checked_result(const checked_result & r) = default;
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checked_result(checked_result && r) = default;
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constexpr /*explicit*/ checked_result(const R & r) noexcept :
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m_e(safe_numerics_error::success),
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m_r(r)
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{}
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constexpr /*explicit*/ checked_result(
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const safe_numerics_error & e,
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const char * msg = ""
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) noexcept :
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m_e(e),
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m_msg(msg)
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{
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assert(m_e != safe_numerics_error::success);
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}
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// permit construct from another checked result type
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template<typename T>
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constexpr /*explicit*/ checked_result(const checked_result<T> & t) noexcept :
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m_e(t.m_e)
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{
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static_assert(
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std::is_convertible<T, R>::value,
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"T must be convertible to R"
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);
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if(safe_numerics_error::success == t.m_e)
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m_r = t.m_r;
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else
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m_msg = t.m_msg;
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}
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constexpr bool exception() const {
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return m_e != safe_numerics_error::success;
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}
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// accesors
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constexpr operator R() const noexcept{
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// don't assert here. Let the library catch these errors
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// assert(! exception());
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return m_r;
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}
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constexpr operator safe_numerics_error () const noexcept{
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// note that this is a legitimate operation even when
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// the operation was successful - it will return success
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return m_e;
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}
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constexpr operator const char *() const noexcept{
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assert(exception());
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return m_msg;
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}
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// disallow assignment
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checked_result & operator=(const checked_result &) = delete;
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};
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template <class R>
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class make_checked_result {
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public:
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template<safe_numerics_error E>
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constexpr static checked_result<R> invoke(
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char const * const & m
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) noexcept {
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return checked_result<R>(E, m);
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}
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};
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} // safe_numerics
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} // boost
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#endif // BOOST_NUMERIC_CHECKED_RESULT
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