Re: [Boost-users] [wave::token_type] Checking if the token_typeinstance is empty

From: Ovanes Markarian (om_boost_at_[hidden])
Date: 2007-04-03 10:20:45

Hartmut,

many thanks for your understanding. Just a small question: Isn't it better to have empty()
function like all other STL containers do? string, vector, ... they all provide empty. I don't
think this is really self explanatory to the user to have is_eoi and sometimes can be confusing,
because as I understand EOI means End of Input. But if I construct a token instance, there is no
end of input, it is empty. It still can internally point to EOI. What is your opinion? But I am
also very happy with is_eoi ;)

With Kind Regards,
Ovanes

On Tue, April 3, 2007 16:02, Hartmut Kaiser wrote:
>
> Ovanes,
>
>> I have a question and may be small interface change to the
>> token_type. Currently there is no "legal" way to check if a
>> token type instance is empty, than using token_id operator
>> and comparing it with T_EOI (which is not really documented,
>> available in the header and default ctor of impl::token_data only).
>>
>> Why did I need it:
>>
>> I have a state machine class which preserves the look ahead.
>> Now when I construct the state machine, the look ahead is
>> default constructed. In particular states I have to
>> distinguish if there is look ahead available or not and take
>> some actions accordingly. Now I would need to rely on the
>> following comparison:
>>
>> BASEID_FROM_TOKEN(T_EOI)==tok.operator token_id();
>>
>> Instead it would be more flexible to write tok.empty(). I am
>> not sure if this convinces you, but at least T_EOI should be
>> documented (I am still using old documentation 1.33.1). The
>> docs should also state that empty token has this type. On the
>> other hand I don't know where else T_EOI is used and how to
>> distinguishe this case then. I would appreciate the empty
>> member function, which can greatly ease the life ;)
>
> I added an 'is_eoi()' function to the token types and will change the
> documentation soon. It's in the Boost CVS::HEAD.
>
> HTH
> Regards Hartmut
>
>
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