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From: reagan@hiyall.enet.dec.com (John R. Reagan)
Newsgroups: comp.lang.pascal
Subject: Re: TP: Exponentiation?
Message-ID: <14539@shlump.nac.dec.com>
Date: 13 Aug 90 16:57:44 GMT
Sender: newsdaemon@shlump.nac.dec.com
Organization: Digital Equipment Corporation
Lines: 36


In article <26C3B78F.8576@ics.uci.edu>, milne@ics.uci.edu (Alastair Milne) writes...
> 
>   Does the standard say anything about how they are implemented?
>   I understand that Wirth decided to omit exponentiation from his
>   original version of the language in part because implementations
>   of the operator tended to be unsatisfactory.

The following is from the standard:

	A factor of the form x**y shall be an error if x is zero and
	y is less than or equal to zero.

	A factor of the form x**y, where x is of integer-type or
	real-type, shall be an error if x is negative; otherwise,
	the value of x**y shall be zero if x is zero, else 1.0 if
	y is zero, else an approximation to (though not necessarily
	calculated by) exp(y*ln(x)).

	A factor of the form x pow y shall be an error if x is zero
	and y is less than or equal to zero.

	The value of a factor of the form x pow y, where x is of
	integer-type, shall be zero if x is zero, else 1 if y
	is zero, else queal to x*(x pow (y-1)) if y is positive,
	else equal to (1 div x) pow (-y) if y is negative.

The quality is an implementation/vendor issue independent of the
definition of the language.  If your vendor provides a slow or
inaccurate exponentation, then complain to your vendor...

---
John Reagan
Digital Equipment Corporation
reagan@hiyall.dec.com
---