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Date: Thu, 25 Nov 2010 17:25:39 +0100
From: =?ISO-8859-15?Q?Michael_Gr=FCnewald?=
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To: Anonymous <swell.k@gmail.com>
References: <20101123210013.GA71784@freebsd.org> <86ipzlg7vt.fsf@gmail.com>
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Cc: Alexander Best <arundel@freebsd.org>, freebsd-questions@freebsd.org
Subject: Re: libm alternative in ports
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Hello all,

Anonymous wrote:
> Alexander Best<arundel@freebsd.org>  writes:
>> does anybody if there's an alternative for libm in the ports dir? i need it,
>> because the newest snapshots of mplayer require log2() and log2f(), which the
>> base libm doesn't support.
>
> for mplayer I'd suggest using code from x264 because both projects use GPLv2+
>
>    #if !HAVE_LOG2F
>    #define log2f(x) (logf(x)/0.693147180559945f)
>    #define log2(x) (log(x)/0.693147180559945)
>    #endif

In `math.h', there is the following definition:

--8<---
#define M_LN2           0.69314718055994530942  /* log e2 */
--8<---

of which you can take advantage for your definition of log2f and log2. 
Note that this macro is not described in math(3).
-- 
Regards,
Michael