Path: utzoo!utgpu!water!watmath!clyde!rutgers!sunybcs!boulder!hao!gatech!mcnc!decvax!decwrl!sun!quintus!ok
From: ok@quintus.UUCP (Richard A. O'Keefe)
Newsgroups: comp.lang.c
Subject: Re: power operator
Summary: min and max once existed
Message-ID: <518@cresswell.quintus.UUCP>
Date: 10 Jan 88 03:40:35 GMT
References: <11182@brl-adm.ARPA> <2197@haddock.ISC.COM>
Organization: Quintus Computer Systems, Mountain View, CA
Lines: 45

In article <2197@haddock.ISC.COM>, karl@haddock.ISC.COM (Karl Heuer) writes:
> Actually, I'd give a higher wish-priority to min and max operators.  They
> could have used "><" and "<>", respectively; the syntax would drive BASIC and
> PASCAL users crazy!  :-)

Some years ago the C compiler I used *did* have min (spelled "/\")
and max (spelled "\/") operators.  These symbols are ever so much better
because they are standard mathematical notation.  Admittedly, when I got
my hands on the compiler, it didn't generate correct code for /\ and \/,
but that was easy to fix.  When we moved "up" to a PCC-based compiler,
conversion was a pain.  It is interesting that macros don't give you
quite the same thing.  Suppose I write
	x = low_bound \/ a /\ high_bound;
This might compile into
	movl	low_bound,r1
	movl	a,r0
	cmpl	r1,r0
	bles	1f
	  movl	r1,r0
    1:	movl	high_bound,r1
	cmpl	r1,r0
	bges	2f
	  movl	r1,r0
    2:	movl	r0,x
Now suppose I have
	#define max(a,b) ((a)<(b)?(b):(a))
	#define min(a,b) ((a)>(b)?(b):(a))
and write
	x = min(max(low_bound,a),high_bound);
Modulo parentheses, this expands to
	x = ( (low_bound < a ? a : low_bound) > high_bound
	    ? (low_bound < a ? a : low_bound) : high_bound );
That's three conditionals, not two.  An optimising compiler could be
expected to recognise the common sub-expression, but why put it to the
trouble?  This "clipping" form is what I mostly used, but maximum or
minimum of more than two elements is reasonably common, and has the
same problem.  The macros make a most unsatisfactory ersatz.

So there is prior art for /\ and \/ in C.
Fortran, of course, has them too.  Apparently Fortran programmers do
not think it a great burden to write MIN(I,J) rather than I/\J.
Do I think it would be a good idea to add the to the standard?  No.
Standards should be DISCOVERED, not INVENTED.  (It was *years*
before COBOL 74 was generally available.  In fact the next version
of the standard was already out...)