maybe.hpp

#ifndef MAYBE_H
#define MAYBE_H
 
// TODO c++17 replaces this with std::optional
template <class T>
class Maybe {
public:
  Maybe(T val_in) : val(val_in), is_valid(true) {}
 
  Maybe() : is_valid(false) {}
 
  bool
  valid() const
  {
    return this->is_valid;
  }
 
  T &
  value()
  {
    // TODO assertion?
    return this->val;
  }
 
  const T &
  value() const
  {
    // TODO assertion?
    return this->val;
  }
 
  operator const T &() const
  {
    // TODO assertion?
    return this->val;
  }
 
  T &
  value_or_default(T & def)
  {
    if (this->is_valid) {
      return this->val;
    } else {
      return def;
    }
  }
 
  const T &
  value_or_default(const T & def)
  {
    if (this->is_valid) {
      return this->val;
    } else {
      return def;
    }
  }
 
  const T &
  value_or_default(const T & def) const
  {
    if (this->is_valid) {
      return this->val;
    } else {
      return def;
    }
  }
 
private:
  T val;
  bool is_valid;
};
 
#endif