Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!amdcad!ames!sdcsvax!sdcc6!ix426
From: ix426@sdcc6.ucsd.EDU (tom stockfish)
Newsgroups: comp.lang.c
Subject: Re: Power proposal for ANSI C
Message-ID: <3594@sdcc6.ucsd.EDU>
Date: 23 Jan 88 07:22:25 GMT
References: <38384@sun.uucp> <2252@haddock.ISC.COM> <3421@ihlpf.ATT.COM> <2335@haddock.ISC.COM> <3474@ihlpf.ATT.COM>
Reply-To: ix426@sdcc6.ucsd.edu.UUCP (tom stockfish)
Organization: University of California, San Diego
Lines: 70

In article <3474@ihlpf.ATT.COM> nevin1@ihlpf.UUCP (00704A-Liber,N.) writes:
> _ __			NEVIN J. LIBER	..!ihnp4!ihlpf!nevin1	(312) 510-6194
>
>1.	(); []; .; ->	(left to right)
>2.	postfix unary	(right to left)
>3.	power		(right to left)
>4.	prefix unary	(right to left)
>5.	*; /; %		(left to right)
>6 and below.	the same as K&R
>
>....  If power were to be added (PLEASE DON'T), I believe it
>should have a precedence below the unaries but above {*; /; and %) and
>associate left to right; it would match closer to the mathematical definition
>this way.

No, please don't propose this precedence.  Expressions like
	
	-x*^2 + 5

will occur often and will make people hate C (where "*^" is the
proposed power op).  Any power operator proposal *must* get
this one right.

>Also, notice that all the right to left operators are either
>assignment or unary;

Wrong.  "? :" groups right to left (K&R appendix notwithstanding).

>having an augmented assignment operator for an operator
>which groups right to left seems inconsistent (and if power is to be added the
>corresponding augmented operator should be added, too).

This seems pretty trivial.  It follows the rule

	a OP= b  <==>  a = a OP b  (except for side effects)

just fine, which is good enough for me.

>Also , by your method
>(++a pow b) == ++(a pow b)
>and
>(a pow b++) == (a pow (b++))
>are how groupings would be done.  This does not look intuitive at all.

Of course not.  Neither does
	
	a+b / c+d

You would write these (if you ever did) as
	
	++ a*^b		/* illegal */

or

	(++a)*^b
and

	a *^ b++ .

I would never try to guess intuitively how "*^" interacted with "++"/"--"
without looking it up in the standard.  Even then, I would add
parens since this would be such an unusual situation.  The expression

	-x*^2 + 5

is an entirely different (and far more important) matter.
	
-- 

||  Tom Stockfisch, UCSD Chemistry   tps@chem.ucsd.edu