[linux-audio-dev] Traps in floating point code

[Jens M Andreasen]

On tis, 2004-06-29 at 17:15, Steve Harris wrote:
> On Tue, Jun 29, 2004 at 10:19:32AM +0200, Benno Senoner wrote:
> >  for (;;)
> >  {
> >    /* Bunch of other code. */
> > 
> >    fullindex += increment;
> >    integer = lrintf(fullindex);
> >    fractional = fullindex - integer;
> 
> I dont think this is right, fractional will be [-0.5, 0.5], rather than
> [0,1] which is more noirmal as lrintf() rounds to the nearest.
> 
> I think you should be using lrintf(floor(x)) or (int)x.

Why not just use modf?

  double fullindex, increment, integer, fraction;
  // int i;

  fullindex += increment;
  fraction   = modf(fullindex, &integer);
  // i = integer;

C99 have float and long double versions as well.

> 
> - Steve