standards/83845: [ patch ] add log2() and log2f() support for libm

[Roman Bogorodskiy]

The following reply was made to PR standards/83845; it has been noted by GNATS.

From: Roman Bogorodskiy <bogorodskiy at gmail.com>
To: "Steven G. Kargl" <kargls at comcast.net>
Cc: bug-followup at FreeBSD.org
Subject: Re: standards/83845: [ patch ] add log2() and log2f() support for libm
Date: Sat, 23 Jul 2005 08:50:13 +0400

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  Steven wrote:
 
 > See standards/82654.
 >=20
 > I have implementations for several C99 long double math functions,
 > and in the process I implemented log2 and logf.  I also wrote or
 
 That's really great, since our libmath is a bit outdated and nobody
 seems to care about that.
 
 > edited the man pages.  IMHO, for log2[fl], we want to use frexp[fl]
 > to break x into x =3D f * 2**n where f is in the range [0.5,1).  We
 > then have  log2(x) =3D n + log2(f).  We can now either evaluate log2(f)
 > as log(f)/log(2) or directly use a polynomial approximation.
 
 That looks reasonable. Actually, I don't care which implementation will
 be used, your or mine or some another, I'd just like to have it
 implemented. But looking at the batch of open standarts PRs I think we
 have no chance to get it committed in the near future. :(
 
 Roman Bogorodskiy
 
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