From: Jeff Dalton
Subject: X-floats closed under addition, etc?
Date:
Message-ID: <7082@skye.ed.ac.uk>
I'd like to know whether double-floats (say) are closed
under addition, subtraction, multiplication, and division.
That is, can I safely say
(the double-float (<op> (the double-float x) (the double-float y)))
for these <op>s?
CLtL II says precision won't be lost. So if double-floats are
different from single-floats, single-floats won't result.
But can some "bigger" float ever result?
The same question can be asked of other float types. My use
of double-float was just to pick a concrete example.
-- jd
Oh boy, an easy question from Jeff. You're slipping....
In article <····@skye.ed.ac.uk> ····@aiai.ed.ac.uk (Jeff Dalton) writes:
>I'd like to know whether double-floats (say) are closed
>under addition, subtraction, multiplication, and division.
I think all the floating point types are closed. P.289 says, "Therefore
when two small floating-point numbers are combined, the result will always
be a small floating-point number." And p.291 says, "the type of the result
of a numerical function is a floating-point number of the largest format
among all the floating-point arguments to the function...."
--
Barry Margolin
System Manager, Thinking Machines Corp.
······@think.com {uunet,harvard}!think!barmar