optional.h

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#ifndef GALOIS_OPTIONAL_H
#define GALOIS_OPTIONAL_H

#include "Galois/LazyObject.h"
#include <cassert>

namespace Galois {

template<typename T>
class optional {
  LazyObject<T> data_;
  bool initialized_;

  void construct(const T& val) {
    data_.construct(val);
    initialized_ = true;
  }

  void assign_impl(const T& val) { get_impl() = val; }

  void destroy() { 
    if (initialized_) {
      data_.destroy();
      initialized_ = false;
    }
  }

  T& get_impl() { return data_.get(); }
  const T& get_impl() const { return data_.get(); }

public:
  typedef bool (optional::*unspecified_bool_type)() const;

  optional(): initialized_(false) { }

  optional(const T& val): initialized_(false) {
    construct(val);
  }

  optional(const optional& rhs): initialized_(false) {
    if (rhs.is_initialized())
      construct(rhs.get_impl());
  }

  template<typename U>
  explicit optional(const optional<U>& rhs): initialized_(false) {
    assign(rhs);
  }

  ~optional() { destroy(); }

  void assign(const optional& rhs) {
    if (is_initialized()) {
      if (rhs.is_initialized())
        assign_impl(rhs.get_impl());
      else
        destroy();
    } else {
      if (rhs.is_initialized())
        construct(rhs.get_impl());
    }
  }

  template<typename U>
  void assign(const optional<U>& rhs) {
    if (is_initialized()) {
      if (rhs.is_initialized())
        assign_impl(rhs.get_impl());
      else
        destroy();
    } else {
      if (rhs.is_initialized())
        construct(rhs.get_impl());
    }
  }

  void assign(const T& val) {
    if (is_initialized())
      assign_impl(val);
    else
      construct(val);
  }

  bool is_initialized() const { return initialized_; }

  optional& operator=(const optional& rhs) {
    assign(rhs);
    return *this;
  }

  template<typename U>
  optional& operator=(const optional<U>& rhs) {
    assign(rhs);
    return *this;
  }

  optional& operator=(const T& val) {
    assign(val);
    return *this;
  }

  T& get() { assert(initialized_); return get_impl(); }
  const T& get() const { assert(initialized_); return get_impl(); }
  T& operator*() { return get(); }
  const T& operator*() const { return get(); }
  T* operator->() { assert(initialized_); return &get_impl(); }
  const T* operator->() const { assert(initialized_); return &get_impl(); }

  operator unspecified_bool_type() const { return initialized_ ? &optional::is_initialized : 0; }
};

}

#endif

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