Is %i an integer? - Adding more facts to the database

< Therefore, from the viewpoint of the implemented function featurep a symbol
< which is declared to be real is also a noninteger.
< 

Not exactly.

< For the practical aim of programming it is necessary to have a convention which
< will work. We might change the behavior of featurep or we might use it as it is
< and document the behavior better.
 
It seems to me that there is a convention and it is reasonable:
if x is declared to be in a set, but not explicitly declared to be
in a subset, then it is assumed not to be in the subset.

The only other convention would be to respond 'unknown'. This would
require one to ask for clarification or handle each case (t/f).

I think it would be more sensible to introduce, for each type, its
negation. At the moment, we have this for even/odd and
rational/irrational.

Leo

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