#+TITLE: GEN routines
* Overview
This document outlines a set of useful GEN routines.
* What exactly is a GEN routine?
A GEN routine is used to describe a function that works
on table (a =SKFLT= array in C). These are usually used to
generate wavetables.

The term "GEN routine" (yes, all caps), is borrowed from
Csound and MUSIC-N languages as
[[http://www.csounds.com/manual/html/ScoreGenRef.html][GENerators for function tables]],
affectionately referred to as "f-tables", which are
essentially just "tables" in the sndkit world.
* Tangled Files
=gen.c= and =gen.h=.

#+NAME: gen.h
#+BEGIN_SRC c :tangle gen.h
#ifndef SK_GEN_SINE
#define SK_GEN_SINE

#ifndef SKFLT
#define SKFLT float
#endif

<<funcdefs>>
#endif
#+END_SRC

#+NAME: gen.c
#+BEGIN_SRC c :tangle gen.c
#include <math.h>
#include <stddef.h>
#include "gen.h"

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

<<funcs>>
#+END_SRC
* sine wave table
The function =sk_gen_sine= generates a sampled period
of a sine wave.

#+NAME: funcdefs
#+BEGIN_SRC c
void sk_gen_sine(SKFLT *tab, unsigned long sz);
#+END_SRC

#+NAME: funcs
#+BEGIN_SRC c
void sk_gen_sine(SKFLT *tab, unsigned long sz)
{
    int i;
    SKFLT step;

    if (sz <= 0) return;

    step = 2 * M_PI / sz;

    for (i = 0; i < sz; i++) {
        tab[i] = sin(i * step);
    }
}
#+END_SRC