Path: utzoo!utgpu!watserv1!watmath!att!pacbell!pacbell.com!ucsd!sdd.hp.com!elroy.jpl.nasa.gov!ncar!midway!tank!stephen
From: stephen@estragon.uchicago.edu (Stephen P Spackman)
Newsgroups: comp.lang.c
Subject: Re: TRUE and FALSE
Message-ID: <STEPHEN.90Sep6221518@estragon.uchicago.edu>
Date: 7 Sep 90 04:15:18 GMT
References: <5398@harrier.ukc.ac.uk> <3686@goanna.cs.rmit.oz.au> <1990Sep6.113259.2109@ifi.uio.no>
Sender: news@midway.uchicago.edu (News Administrator)
Organization: University of Chicago CILS
Lines: 47
In-Reply-To: jar@ifi.uio.no's message of 6 Sep 90 11:32:59 GMT

To pick up on a couple of comments:

In article <1990Sep6.113259.2109@ifi.uio.no> jar@ifi.uio.no (Jo Are Rosland) writes:

   Why can't I do this in C?  The && and || operators are defined
   to return either 0 or 1.  With the Lisp semantics I could write
   code like:

	   return f() || g();

   instead of:

	   a = f();
	   if (a)
		   return a;
	   else
		   return g();

   This is useful eg. when f() and g() return pointers (maybe in
   some sort of search, where we only want to call the second
   function if the first one fails.)  And I even think the first
   version reads better.

The single most important case is, of course, when f() and g() return
functions. You could code all of that ecchy high-level
strategy-finding code in this style:

	return (f() || g())(x);

And if THAT ain't clarity, I don't know what is.

In article <1990Sep6.113259.2109@ifi.uio.no> jar@ifi.uio.no (Jo Are Rosland) writes:

   The is_true() macro is almost as useful as a macro you might
   write to return the numeric value of its argument, i.e.:

   a = value_of( b ) + value_of( c );

I'm in favour, though I'd like to see a prefix operator for this.
There damn well ought to be an operator for extracting values from
variables, so people don't confuse them with constants.

And to encourage them to USE constants.

(And it's been done in real languages, honest).

stephen p spackman  stephen@estragon.uchicago.edu  312.702.3982