Truncating a fixed-point value

[Adam Beneschan <adam@irvine.com>]

I must be suffering from an embarrassing mental block, because I'm
sure there's a simple solution, but I can't see what it is.

I have a value X of a fixed-point type, X >= 0.0, and I need to
compute Floor(X) as an Integer.  'Truncation and 'Floor aren't defined
for fixed-point types; the type conversion Integer(X) rounds; and
Integer(X-0.5) fails if X=0.0.

How do others do this?  Or do I have to resort to an IF statement (or
conditional expression in Ada 2012) to handle the different cases?

               -- Adam