Re: [Boost-users] [variant] ideas needed

From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2008-02-21 14:12:40

AMDG

Olaf wrote:
>
> That's correct. If it contains a double the string value is empty.
>
>   
>> The variant cannot contain a string that is not "NA"
>>
>> struct available
>>       : public boost::static_visitor<bool>
>> {
>>       bool operator()( const double&) const
>>       {
>>           return true;
>>       }
>>
>>       bool operator()( const string& lhs) const
>>       {
>>           assert(lhs == "NA");
>>
>>           return false; //???
>>       }
>> };
>>     
>
> May this work? There is always a string - empty or holding "NA".
>   

I don't quite understand.  variant<double, string> holds either a double
or a string at any one time, never both.  If the variant holds a double then
the overload of operator() for double will be called, if a string then 
the overload
for string will be called instead.

In Christ,
Steven Watanabe