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

Leo Butler wrote:
> < 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.
>   
This seems really bad.

> 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
>
>