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From: bright@dataio.Data-IO.COM (Walter Bright)
Newsgroups: misc.misc,comp.lang.c
Subject: Re: Printing binary (was: Re: Why college?)
Message-ID: <1398@dataio.Data-IO.COM>
Date: Fri, 23-Oct-87 14:21:51 EST
Article-I.D.: dataio.1398
Posted: Fri Oct 23 14:21:51 1987
Date-Received: Sun, 25-Oct-87 16:53:10 EST
References: <35@ateng.UUCP> <3194@sol.ARPA> <2783@xanth.UUCP> <235@snark.UUCP> <2072@watcgl.waterloo.edu>
Reply-To: bright@dataio.UUCP (Walter Bright)
Organization: Data I/O Corporation; Redmond, WA
Lines: 59
Xref: mnetor misc.misc:1964 comp.lang.c:5105

In article <2072@watcgl.waterloo.edu> smvorkoetter@watmum.waterloo.edu (Stefan M. Vorkoetter) writes:
>In article <235@snark.UUCP> eric@snark.UUCP (Eric S. Raymond) writes:
>>I thought about the standard ways to do this, (essentially, crack the sucker
>>into powers-of-two internally via repeated integer-divide and modulo
>>operations) went *ugh*, and then had a flash that gave me an amusing
>>alternate solution. Here it is: (warning! this is untested and off-the-cuff)
>
>There is a very quick way to do this using only the <<, >>, and & operators:
>
>#define	BITS		32			/* or 16 */
>
>void print_binary(n)
>int n;
>{
>	int i;
>
>	for(i = 0; i < BITS; i++) {
>		printf("%1d",(n >> (BITS - 1)) & 1);
>		n <<= 1;
>	}
>}


Newsgroups: misc.misc,comp.lang.c
Subject: Re: Printing binary (was: Re: Why college?)
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References: <35@ateng.UUCP> <3194@sol.ARPA> <2783@xanth.UUCP> <235@snark.UUCP> <2072@watcgl.waterloo.edu>
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In article <2072@watcgl.waterloo.edu> smvorkoetter@watmum.waterloo.edu (Stefan M. Vorkoetter) writes:
<In article <235@snark.UUCP< eric@snark.UUCP (Eric S. Raymond) writes:
<<I thought about the standard ways to do this, (essentially, crack the sucker
<<into powers-of-two internally via repeated integer-divide and modulo
<<operations) went *ugh*, and then had a flash that gave me an amusing
<<alternate solution. Here it is: (warning! this is untested and off-the-cuff)
<There is a very quick way to do this using only the <<, >>, and & operators:
<#define	BITS		32			/* or 16 */
<void print_binary(n)
<int n;
<{	int i;
<	for(i = 0; i < BITS; i++) {
<		printf("%1d",(n >> (BITS - 1)) & 1);
<		n <<= 1;
<	}
<}

I simply modified the printf() format to add a %b format specifier for
binary format. It added a case and 1 line of code. Also, things like
%04b were gotten for free. I imagine that this is equally trivial for
other compilers.

Anyone know why ANSI C doesn't specify this? I wrote them a letter which
they haven't replied to.