Path: utzoo!utgpu!water!watmath!clyde!rutgers!ames!amdcad!sun!pitstop!sundc!seismo!uunet!mcvax!dik
From: dik@cwi.nl (Dik T. Winter)
Newsgroups: comp.lang.c
Subject: Re: Power proposal for ANSI C
Keywords: power exponentiation **
Message-ID: <7487@boring.cwi.nl>
Date: 10 Jan 88 08:16:14 GMT
References: <38384@sun.uucp>
Organization: CWI, Amsterdam
Lines: 26

In article <38384@sun.uucp> dgh%dgh@Sun.COM (David Hough) writes:
 >      Recommendation: Add a power operator **, with the
 >      --------------
 > precedence of a cast operator, so that a cast expression can
 > be
 > 
 >         cast-expression ** cast-expression
 > 
 > In b ** n, the base expression b may be an integral or
 > floating expression, but the exponent expression n must be
 > an integral expression.  If n == 0, then the result is 1
 > cast to the type of b.  If n > 0, then the result is the usual:
 > the value of b is multiplied together n-1 times.  If n < 0,
 > then the result is the reciprocal of b ** (-n), which is 0
 > if b is an integral expression >= 2.

Note that these semantics are wrong.  What if n<0 and b**(-n)
overflows while b**n does not underflow?  According to the stated
semantics this should trap an overflow or return 0.0.  On the
other hand if b**n for negative n is defined as (1/b)**(-n) we
lose precision.  So is there anybody who can come up with a proper
definition of the power operator?
-- 
dik t. winter, cwi, amsterdam, nederland
INTERNET   : dik@cwi.nl
BITNET/EARN: dik@mcvax