Option.h

/*
 * $Id$
 * Copyright (c) 2006, IRIT-UPS <casse@irit.fr>.
 *
 * elm/util/Option.h -- interface for Option class.
 */
#ifndef ELM_UTIL_OPTION_H
#define ELM_UTIL_OPTION_H

#include <elm/assert.h>
#include <elm/type_info.h>

namespace elm {

// OptionalNone value
class OptionalNone {
};
extern const OptionalNone none;


// Optional value
template <class T> class Option {
public:
    inline Option(void): one(false) { }
    inline Option(const OptionalNone& none): one(false) { }
    inline Option(T value): one(true) { type_info<T>::put(val, value); }
    inline Option(const Option<T> &opt): one(opt.one), val(opt.val) { }
    inline bool isOne(void) const { return one; }
    inline bool isNone(void) const { return !one; }
    inline T value(void) const
        { ASSERTP(one, "no value in option"); return type_info<T>::get(val); }
    
    inline operator bool(void) const { return isOne(); }
    inline T operator*(void) const { return value(); }
    inline operator T(void) const { return value(); }
    inline Option<T>& operator=(const Option<T>& opt)
        { one = opt.one; if(one) val = opt.val; return *this; }
    inline Option<T>& operator=(T value)
        { one = true; type_info<T>::put(val, value); return *this; }

private:
    bool one;
    typename type_info<T>::embed_t val;
};


// Fast Option building
template <class T>
inline Option<T> some(T val) { return Option<T>(val); };

} // elm

#endif /* ELM_UTIL_OPTION_H */