Path: utzoo!attcan!uunet!snorkelwacker.mit.edu!bloom-beacon!jfc
From: jfc@athena.mit.edu (John F Carr)
Newsgroups: comp.std.c
Subject: Re: floating point constant folding
Message-ID: <1990Nov14.192231.29728@athena.mit.edu>
Date: 14 Nov 90 19:22:31 GMT
References: <8191@star.cs.vu.nl> <1990Nov13.174025.1520@zoo.toronto.edu>
Sender: daemon@athena.mit.edu (Mr Background)
Organization: Massachusetts Institute of Technology
Lines: 17

In article <1990Nov13.174025.1520@zoo.toronto.edu>
	henry@zoo.toronto.edu (Henry Spencer) writes:
>Observable results include overflow exceptions and the values
>of data items written out to files.

Overflows of types other than unsigned integers are undefined, so a
conforming compiler could rearrange float expressions that would
overflow in the target machine's floating point format.  The standard
allows calculations to be in greater precision than the types involved.

In practice, this means if the compiler simplifies floating point
expressions involving constants, it must use the target float format,
or a format with more bits than the target (both range and precision
must be at least as great as the target).

--
    John Carr (jfc@athena.mit.edu)