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Date: 25 Nov 91 06:09:00 GMT
From: csus.edu!wupost!spool.mu.edu!munnari.oz.au!metro!cluster!swift!sunaus!ass
ip.csasyd!condor!daves@ucdavis.ucdavis.edu  (Dave Smart)
Subject: Re: Red-faced professor gets bitten in search for portability
Message-ID: <daves.691049340@condor>
List-Id: <comp.lang.ada>

To follow up my own post, I've been reminded that my algorithm - and Mike 
Murphy's and both of Mike Feldman's - don't reproduce the Pascal trunc action 
for negative numbers.  E.g. -3.75 becomes -4 rather than -3.  In my own case, o
f
course, I was simply reproducing the action of Mike Murphy's algorithm :-).

There are tricky ways of getting the result right for negative values.  In 
Pascal, I'd probably use the abs () and sign () functions.  However, KISS:

  function trunc (number: float) return integer is
  begin
    if number >= 0.0 then                        -- positive cases
      if float (integer (number)) > number then    -- does it round up?
        return integer (number) - 1;               -- yes - stop it!
      else
        return integer (number);                   -- no - ok as it is.
      end if;
    else                                         -- negative cases
      if float (integer (number)) < number then    -- does it round down?
        return integer (number) + 1;               -- yes - stop it!
      else
        return integer (number);                   -- no - ok as it is.
      end if;
    end if;
  end trunc;

Dave
-- 
David Smart, Computer Sciences of Australia.
Net: daves@assip.csasyd.oz.au