Path: utzoo!attcan!uunet!munnari.oz.au!mudla!ok
From: ok@mudla.cs.mu.OZ.AU (Richard O'Keefe)
Newsgroups: comp.lang.c
Subject: Re: binary constants (??)
Keywords: macro, constant, binary
Message-ID: <2765@munnari.oz.au>
Date: 21 Nov 89 07:06:52 GMT
References: <305@frf.omron.co.jp> <602@chem.ucsd.EDU> <7065@ficc.uu.net>
Sender: news@cs.mu.oz.au
Lines: 54

In article <7065@ficc.uu.net>, peter@ficc.uu.net (Peter da Silva) writes:
> For most cases binary constants are just fine in HEX. But for image data
> it's a real pain.

Who said everything the C compiler sees had to be written by hand?
If you need binary numbers, use m4.  It's a UNIX utility, and there is
a public domain version by Ozan Yigit.

Here's all you need for binary numbers, and you don't really
need rhead and rtail as separate macros:

define(rhead,`substr($1,decr(len($1)),1)')dnl
define(rtail,`substr($1,0,decr(len($1)))')dnl
define(bin,`ifelse($1,,0,`eval(bin(rtail($1))*2+rhead($1))')')dnl

With the aid of this, Peter da Silva would just write
    struct sprite smileyface =
	{
	    0, 0, 32, 011,
	    {
		bin(0000000000000000),
		bin(0000111111110000),
		bin(0011000000001100),
		bin(0100011001100010),
		bin(0100000000000010),
		bin(0101110000111010),
		bin(0100100000010010),
		bin(0100011111100010),
		bin(0011000000001100),
		bin(0000111111110000),
		bin(0000000000000000),
	    }
	};

If we change the definition of bin to
define(bin,`ifelse($1,,0,`eval(bin(rtail($1))*2+
	    ifelse(rhead($1),0,0,rhead($1),_,0,1))')')dnl

the bit map could be either as shown above OR as shown below

		bin(________________),
		bin(____@@@@@@@@____),
		bin(__@@________@@__),
		bin(_@___@@__@@___@_),
		bin(_@____________@_),
		bin(_@_@@@____@@@_@_),
		bin(_@__@______@__@_),
		bin(_@___@@@@@@___@_),
		bin(__@@________@@__),
		bin(____@@@@@@@@____),
		bin(________________),

I find this version clearer still.  (By the way, it took 20 minutes to
knock this together, I'm rather rusty with M4.)