lean2/src/util/optional.h

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/*
Copyright (c) 2013 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Author: Leonardo de Moura
*/
#pragma once
#include "util/debug.h"
namespace lean {
/**
\brief Simple optional template. This is a naive replacement for C++14 optional.
We will delete it as soon optional is supported in g++ and clang++.
*/
template<typename T>
class optional {
bool m_some;
union {
T m_value;
};
public:
optional():m_some(false) {}
optional(optional & other):m_some(other.m_some) {
if (m_some)
new (&m_value) T(other.m_value);
}
optional(optional const & other):m_some(other.m_some) {
if (m_some)
new (&m_value) T(other.m_value);
}
optional(optional && other):m_some(other.m_some) {
if (m_some)
new (&m_value) T(std::forward<T>(other.m_value));
}
explicit optional(T const & v):m_some(true) {
new (&m_value) T(v);
}
explicit optional(T && v):m_some(true) {
new (&m_value) T(std::forward<T>(v));
}
template<typename... Args>
explicit optional(Args&&... args):m_some(true) {
new (&m_value) T(std::forward<Args>(args)...);
}
~optional() {
if (m_some)
m_value.~T();
}
explicit operator bool() const { return m_some; }
T const * operator->() const { lean_assert(m_some); return &m_value; }
T * operator->() { lean_assert(m_some); return &m_value; }
T const & operator*() const { lean_assert(m_some); return m_value; }
T & operator*() { lean_assert(m_some); return m_value; }
T const & value() const { lean_assert(m_some); return m_value; }
T & value() { lean_assert(m_some); return m_value; }
template<typename... Args>
void emplace(Args&&... args) {
if (m_some)
m_value.~T();
m_some = true;
new (&m_value) T(args...);
}
optional& operator=(optional const & other) {
if (this == &other)
return *this;
if (m_some)
m_value.~T();
m_some = other.m_some;
if (m_some)
new (&m_value) T(other.m_value);
return *this;
}
optional& operator=(optional && other) {
lean_assert(this != &other);
if (m_some)
m_value.~T();
m_some = other.m_some;
if (m_some)
new (&m_value) T(std::forward<T>(other.m_value));
return *this;
}
optional& operator=(T const & other) {
if (m_some)
m_value.~T();
m_some = true;
new (&m_value) T(other);
return *this;
}
optional& operator=(T && other) {
if (m_some)
m_value.~T();
m_some = true;
new (&m_value) T(std::forward<T>(other));
return *this;
}
friend bool operator==(optional const & o1, optional const & o2) {
if (o1.m_some != o2.m_some)
return false;
else
return !o1.m_some || o1.m_value == o2.m_value;
}
friend bool operator!=(optional const & o1, optional const & o2) {
return !operator==(o1, o2);
}
};
template<typename T> optional<T> some(T const & t) { return optional<T>(t); }
template<typename T> optional<T> some(T && t) { return optional<T>(std::forward<T>(t)); }
// The following macro creates a template specialization optional<P>, where P
// is an intrusive smart pointer that does not let "customers" point to nullptr.
// That is, if a customer have 'P x', then x is not a pointer to nullptr.
// Requirements:
// - P must declare optional<P> as a friend.
// - P must handle the nullptr case even if it does not let "customers" point to nullptr
// - P must have a field m_ptr a pointer to the actual value.
#define SPECIALIZE_OPTIONAL_FOR_SMART_PTR(P) \
template<> class optional<P> { \
P m_value; \
public: \
optional():m_value(nullptr) {} \
optional(optional const & other):m_value(other.m_value) {} \
optional(optional && other):m_value(std::forward<P>(other.m_value)) {} \
explicit optional(P const & v):m_value(v) {} \
explicit optional(P && v):m_value(std::forward<P>(v)) {} \
\
explicit operator bool() const { return m_value.m_ptr != nullptr; } \
P const * operator->() const { lean_assert(m_value.m_ptr); return &m_value; } \
P * operator->() { lean_assert(m_value.m_ptr); return &m_value; } \
P const & operator*() const { lean_assert(m_value.m_ptr); return m_value; } \
P & operator*() { lean_assert(m_value.m_ptr); return m_value; } \
P const & value() const { lean_assert(m_value.m_ptr); return m_value; } \
P & value() { lean_assert(m_value.m_ptr); return m_value; } \
optional & operator=(optional const & other) { m_value = other.m_value; return *this; } \
optional& operator=(optional && other) { m_value = std::forward<P>(other.m_value); return *this; } \
optional& operator=(P const & other) { m_value = other; return *this; } \
optional& operator=(P && other) { m_value = std::forward<P>(other); return *this; } \
friend bool operator==(optional const & o1, optional const & o2) { \
return static_cast<bool>(o1) == static_cast<bool>(o2) && (!o1 || o1.m_value == o2.m_value); \
} \
friend bool operator!=(optional const & o1, optional const & o2) { \
return !operator==(o1, o2); \
} \
};
}