[PD] efficient approximation of trig functions for hi pass formula (was: could vanilla borrow iemlib's hi pass filter recipe?)

Martin Peach chakekatzil at gmail.com
Wed Oct 19 20:05:02 CEST 2016

On Wed, Oct 19, 2016 at 1:07 PM, katja <katjavetter at gmail.com> wrote:

> On Wed, Oct 19, 2016 at 4:25 PM, Jonathan Wilkes <jancsika at yahoo.com>
> wrote:
> > When implemented in C, which approach takes the least amount of time
> > to read, reason about, and fully comprehend?
> That is an important question. Pd code is full of clever tricks and
> bit hacks for dsp efficiency. What is the origin of q8_rsqrt(), why
> and how does it work? What about PD_BIGORSMALL() in m_pd.h? And the
> mysterious UNITBIT32 number in d_osc.c? Ideally such code should be
> commented not only to denote its function (if necessary) but also to
> reference the origin so you may be able to find info.
I agree that Pd's code is very sparsely commented. I imagine Miller keeps
another copy with all the comments.
I was mystified by UNITBIT32 as well. I tried to explain it in the comments
of my sqosc~ object at

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