Path: utzoo!mnetor!uunet!husc6!cmcl2!yale!bunker!garys
From: garys@bunker.UUCP (Gary M. Samuelson)
Newsgroups: comp.lang.c
Subject: Re: Bitmap constants in C code
Message-ID: <3137@bunker.UUCP>
Date: 23 Dec 87 20:08:52 GMT
Organization: Bunker Ramo, an Olivetti Company, Shelton, CT
Lines: 44
Keywords: binary, integer, literal

In (belated) response to George Zipperlan and Doug Moen:

George wanted to enter binary constants (e.g., 0b#01000100).
Doug suggested some tricky defines:

	#define A +128
	#define B +64
	#define C +32
	...

	char pattern[] = { A _ C _ E _ F _, ... };

This allows binary constants in ANSI C.  I applaud Doug's
ingenuity, and suggest the following alternative:

#define X )*2+1
#define _ )*2
#define b ((((((((0		/* For byte building */
#define w ((((((((((((((((0	/* For word building */

George's original problem (bit pattern for an arrow) is thus:

static unsigned short CursorPattern[] =
{
	w X X X X X X X X _ _ _ _ _ _ _ _,
	w X _ _ _ _ _ X _ _ _ _ _ _ _ _ _,
	w X _ _ _ _ X _ _ _ _ _ _ _ _ _ _,
	w X _ _ _ _ _ X _ _ _ _ _ _ _ _ _,
	w X _ _ _ _ _ _ X _ _ _ _ _ _ _ _,
	w X _ X _ _ _ _ _ X _ _ _ _ _ _ _,
	w X X _ X _ _ _ _ _ X _ _ _ _ _ _,
	w X _ _ _ X _ _ _ X _ _ _ _ _ _ _,
	w _ _ _ _ _ X _ X _ _ _ _ _ _ _ _,
	w _ _ _ _ _ _ X _ _ _ _ _ _ _ _ _
};

There are three improvements over Doug's solution:
1. Unary '+' is not required.
2. You don't have to remember which letter goes in which column.
3. It is just as easy to build any size of binary datum.

Gary Samuelson

Should I have saved those macros for the next obfuscated C contest?