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From: kolstad@parsec.UUCP
Newsgroups: net.lang.c
Subject: Re: compile-time function - (nf)
Message-ID: <3269@uiucdcs.UUCP>
Date: Sat, 15-Oct-83 22:51:30 EDT
Article-I.D.: uiucdcs.3269
Posted: Sat Oct 15 22:51:30 1983
Date-Received: Mon, 17-Oct-83 04:44:14 EDT
Lines: 12

#R:hp-dcde:20000001:parsec:37300002:000:347
parsec!kolstad    Oct 15 18:35:00 1983

Here's how I did LOG2:

#define LOG2(x)  ((x)<=2?1: (x)<=4?2: (x)<=8?3: (x)<=16?4: \
	 (x)<=32?5: (x)<=64?6: (x)<=128?7:  (x)<=256?8: (x)<=512?9: \
	 (x)<=1024?10:  (x)<=2048?11:12 )

NB:  The C compiler will evaluate this expression to a single constant
	if it is supplied with a constant argument.  The preprocessor
	does NOT do the reduction.