[R] Type of multi-valued variable

[Fan]

Hi,

I've read in the past a thead in the R discussion list
about the multi-valued type variable (what was called checklist).
At the moment Gregory had intention to add some general code
in his gregmisc package.

I'm wondering if there's some general code / packages available ?

A general class for taking account this type of variable 
would be very useful in the domain of survey processings,
as multi-responses questions are often used. 
The simple operations applied to these variables are holecount, 
cross tabulations with others variables, transformation to single 
coded variables like number of responses, etc.

Thanks in advance for any help
--
Fan