Re: Integer truncation and other recipes

[ncohen@watson.ibm.com (Norman H. Cohen)]

In article <JSA.96Jun4154923@organon.com>, jsa@organon.com (Jon S Anthony)
writes: 

|> In article <DsGC9A.4KD@bton.ac.uk> je@bton.ac.uk (John English) writes: 
|>
|> > : > In Ada, how do you convert from a real to an integer by truncation?
|> > : > That is, how would you convert a value such as 1.9 to 1?
|> > : Go to index and find entry: 
|> > :   Truncation attribute
|> >
|> > Fine for floating point types, but you're out of luck if you want to truncate
|> > *fixed point* types, for which the 'Truncation attribute isn't available...
|>
|> First convert to floating point...

Not a very satisfying answer.  Suppose you want to delay until the next
time the minute hand sweeps past the 12.  It would be nice to be able to
write: 

   declare
      Now         : Duration := Ada.Calendar.Seconds(Ada.Calendar.Clock);
      This_Minute : Duration := Duration'Floor(Now/60.0) * 60.0;
                    -- ILLEGAL!!! There is not really a Duration'Floor
                    --    attribute!
      Next_Minute : Duration := This_Minute + 60.0;
   begin
      delay until Next_Minute;
   end;

Duration(Float'Floor(Float(Now)/60.0)) is a poor substitute for
Duration'Floor(Now/60.0).

I think the failure to generalize certain of the floating-point
attributes to fixed-point types was an unfortunate oversight.

--
Norman H. Cohen    ncohen@watson.ibm.com