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

From: Ovanes Markarian (om_boost_at_[hidden])
Date: 2007-04-03 08:37:54

Hello Hartmut,

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 ;)

With Kind Regards,

Ovanes Markarian