I think Ive made a bad choice of a variable name here.Actually tf is the
wdf in this code  .In boolean normalization,we return tfn as 0 if wdf (tf)
is 0 and tfn as  1 otherwise.
In tf-idf scheme ,tf is the within document frequency.

On Mon, Mar 11, 2013 at 8:40 AM, Olly Betts <notifications@github.com>wrote:

> In xapian-core/weight/tfidfweight.cc:
>
> > +
> > +double
> > +TfIdfWeight::get_maxextra() const
> > +{
> > +    return 0;
> > +}
> > +
> > +// Return normalized tf,idf and weight depending on the normalization string
> > +double
> > +TfIdfWeight:: get_tfn(Xapian::termcount tf, const char c) const
> > +{
> > +    switch (c) {
> > +        case 'N':
> > +            return tf;
> > +        case 'B':
> > +            if (tf==0) return 0;
>
> But wdf != tf...
>
> If the tf is zero, then the term doesn't exist in the database, so it
> shouldn't be possible for us to get here.
>
> —
> Reply to this email directly or view it on GitHub<https://github.com/xapian/xapian/pull/6/files#r3311772>
> .
>