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From: dave@inset.UUCP (Dave Lukes)
Newsgroups: net.lang.c
Subject: Re: How does one construct a mask for the MS bit?
Message-ID: <520@inset.UUCP>
Date: Wed, 20-Mar-85 12:49:07 EST
Article-I.D.: inset.520
Posted: Wed Mar 20 12:49:07 1985
Date-Received: Tue, 26-Mar-85 06:56:56 EST
References: <8849@brl-tgr.ARPA>, <169@dmsd.UUCP>
Organization: The Instruction Set Ltd, London
Lines: 42

Newsgroups: net.lang.c
Subject: Re: How does one construct a mask for the MS bit?
References: <8849@brl-tgr.ARPA>, <169@dmsd.UUCP>

> seems that this should work:
> 
> #define MSB(a)		(1<<((sizeof a) * 8 - 1))
> 
> for most un*x machines.
> -- 
> John Bass

MOST UN*X machines?? Go suck a Honeywell !! (or A BBN)
====
``Well, it works on all the machines I use''
is a great attitude if you can afford it: not everyone can (or wants to!).

Even if you are willing to have your code break on a machine with one more
bit, at least COMMENT the fact beforehand.
	      =======

Also, if the the byte/word/long ... size is so important:


		WORK   IT   OUT !!!!!!!!!!
		==========================

How's this:

	bitsperword() {

		unsigned int i = ~0;
		int nbits = 0;

		do
			nbits++;
		while((i >>= 1) != 0);
		return nbits;
	}

		Yours portably,
			Dave Lukes