# [FFmpeg-devel] [PATCH] WIP/eval: document recently added random(), hypot(), gcd().

Michael Niedermayer michaelni at gmx.at
Mon Oct 10 22:16:30 CEST 2011

```On Mon, Oct 10, 2011 at 09:47:30PM +0200, Clément Bœsch wrote:
> On Sat, Oct 08, 2011 at 02:35:25PM +0200, Michael Niedermayer wrote:
> > On Sat, Oct 08, 2011 at 12:26:34PM +0200, Clément Bœsch wrote:
> > > On Sat, Oct 08, 2011 at 12:25:00PM +0200, Clément Bœsch wrote:
> > > > ---
> > > > I took av_gcd() description to document gcd(), but I'm not sure for random()
> > > > (it seems normalized but I didn't check). And for hypot(), I just don't know
> > > > what it is… :)
> >
> > random is a PRNG with value between 0.0 and 1.0 using the argument as
> > index into our array of variables and the indexed to value as
> > seed/state
> > and array of variables in the sense of ld() st()
> >
> > hypot() is just the same as the C function
> > stolen from the fine manual:
> >  -- Function: double hypot (double X, double Y)
> >  -- Function: float hypotf (float X, float Y)
> >  -- Function: long double hypotl (long double X, long double Y)
> >      These functions return `sqrt (X*X + Y*Y)'.  This is the length of
> >      the hypotenuse of a right triangle with sides of length X and Y,
> >      or the distance of the point (X, Y) from the origin.  Using this
> >      function instead of the direct formula is wise, since the error is
> >      much smaller.  See also the function `cabs' in *note Absolute
> >      Value::.
>
> Thanks, then what about the attached patch?

LGTM

[...]

--

Everything should be made as simple as possible, but not simpler.
-- Albert Einstein
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