#ifndef OPT_HPP_
#define OPT_HPP_

#include "symbol.hpp"

template< class Symbol >
class opt
    : public symbol
{
public:
    template< class CharType >
    constexpr opt( const_string< CharType > str , std::size_t begin = 0 )
        : symbol
        (
            begin == invalid_index ?
                invalid_index :
                Symbol( str , begin ).valid() ?
                    Symbol( str , begin ).end() :
                    begin
        ) ,
        m_str( str ) ,
        m_begin( begin )
    {
    }
    constexpr Symbol get()
    {
        return Symbol( m_str , m_begin );
    }
    constexpr operator bool()
    {
        return Symbol( m_str , m_begin ).valid();
    }
private:
    const_string< char > m_str;
    const std::size_t m_begin;
};

#endif