[Zope] ZCatalog range searches with floats

[Seb Bacon]

I'd like a quick piece of Catalog advice before I allow myself to get sucked
into it with no chance of escape.

I've got a few objects in the catalog, which have an attribute which may be
a float, or may be blank.  I want to do the equivalent of:

"select * from catalog where attr > 4.53"

I'm getting back *everything* in the catalog, whatever the value of the
attribute.  Before I dive in and work out exactly what's going on, I wanted
to make sure this kind of thing is currently possible - every example of
using the 'range' modifier currently uses a DateTime object for comparison.

seb