[LAU] OT(ish): Strange coding problem (audio related)

[fons at kokkinizita.net]

On Fri, Jan 28, 2011 at 02:02:36PM +0100, Philipp Überbacher wrote:

> rant_begin
>     Why can't log mean the same thing everywhere? Why does it need to be
>     base e here and base 10 there? Why is there no consistency?
>     And why is there no proper logarithmus dualis function? Because you
>     can simply do log(n)/log(2)? We've just seen how well this works.
>     How about:
>         log() - base 10
>         ln() - base e - logarithmus naturalis
>         ld() - base 2 - logarithmus dualis
> rant_end

Libm has log(), log10, and log2().
 
> The next obvious question is: Does the inaccuracy reliably result in
> values bigger than 11?

No.

If the input is a power of two, and you expect an integer as
a result, just do

  k = (int)(log2(x) + 1e-6)

or

  k = (int)(log(x)/log(2) + 1e-6)

or

  int m, k;
  for (k = 0, m = 1; m < x; k++, m <<= 1);

  which will round up if x is not a power of 2.

Ciao,

-- 
FA

There are three of them, and Alleline.