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From: darryl@ISM780.UUCP
Newsgroups: net.lang.c
Subject: Re: Re: No Such Thing (errata)
Message-ID: <30000010@ISM780.UUCP>
Date: Fri, 30-Aug-85 08:38:00 EDT
Article-I.D.: ISM780.30000010
Posted: Fri Aug 30 08:38:00 1985
Date-Received: Sun, 1-Sep-85 05:50:41 EDT
References: <1007@brl-tgr.UUCP>
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Nf-ID: #R:brl-tgr:-100700:ISM780:30000010:000:1772
Nf-From: ISM780!darryl    Aug 30 08:38:00 1985


>To me, the mapping TRUE -> 0 and FALSE -> non-zero doesn't seem obvious,

That's probably because you have it turned around... TRUE -> nonzero,
FALSE -> 0.

>In assembler, one often writes the following (I'm using pseudocode
>rather than any particular assembler):
>
>        compare two values
>        jumpto stuff  if zero
>
>Which is the assembler equivalent of
>
>        if (value1 == value2)
>          <do stuff> ;

Once again, you seemed slightly confused...  These two don't exactly match
each other.  In assembler, you probably jump around the <do stuff> code.
If you do, then you want to jump on nonzero, assuming the C code is what
you really wanted.  In any event, C's approach is very assembler-like;
any conditional has an implicit comparison against zero, just like most
machines support.

>When I was in high school I was programming TRS-80's in both assembler
>and BASIC, and I had lots of trouble remembering whether BASIC
>represented truth as zero or -1.  No such memory is needed for the
>assembler, of course, since comparison is merely done by subtraction (a
>compare instruction is usually just a subtract instruction that doesn't
>store the result anywhere), so it is obvious what the zero indicator
>means.  It is not so obvious to me that in C 0 should mean false and 1
>mean true.

If you don't feel comfortable with a language, use another or spend the
time and effort to become comfortable.  C is certainly not my choice for
a beauty contest, but one can craft large, useful programs that can
then be run, reasonably efficiently, on many machines.  I suppose that
there is some beauty to that, after all.

	    --Darryl Richman, INTERACTIVE Systems Corp.
	    ...!cca!ima!ism780!darryl
	    The views expressed above are my opinions only.