Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!cs.utexas.edu!texbell!ficc!peter
From: peter@ficc.ferranti.com (Peter da Silva)
Newsgroups: comp.lang.misc
Subject: Re: Compiler Costs
Message-ID: <8OJ4M.4@ficc.ferranti.com>
Date: 9 Jul 90 12:17:26 GMT
References: <1797@apctrc.UUCP> <103726@convex.convex.com> <2324@l.cc.purdue.edu>
Reply-To: peter@ficc.ferranti.com (Peter da Silva)
Organization: Xenix Support, FICC
Lines: 20

In article <2324@l.cc.purdue.edu> cik@l.cc.purdue.edu (Herman Rubin) writes:
> The function is frexp(x,&n).  The argument x is a double precision floating
> point number.  The result is to be that number scaled down by a power of 
> 2 so that the absolute value is between .5 and 1, with the power stored in
> the location &n.

I suspect that something like this will work:

	double frexp(x,n)
	double x;
	int *n;
	{
		x = NORMALISE(x);
		*n = ((long *)&x)[EXPONENT_WORD] & EXPONENT_BITS;
		((long *)&x)[EXPONENT_WORD] &= ~EXPONENT_BITS;
		return x;
	}

You didn't say it had to be portable C. For most machines this will come
down to 2 or 3 instructions, given a decent compiler.
-- 
Peter da Silva.   `-_-'
+1 713 274 5180.
<peter@ficc.ferranti.com>