to_char(0,'9999.99') -> ".00"

Dear All,

I was a bit surprised to find that

    to_char(0,'9999.99')

returns    .00 rather than 0.00.

Is this a bug or a feature?  How do I get what I want?

(This is with 7.4.2.  Appologies if it is a known problem.  The search
form in the list archives seems to split words on _, so looking for
to_char finds lots of pages that just say 'char'.)

Regards,

Phil Endecott.