from a cimport *
cdef extern from "a/lpf.h":
ctypedef struct a_lpf:
a_float alpha
a_float output
a_float a_lpf_gen(a_float fc, a_float ts)
void a_lpf_init(a_lpf *ctx, a_float alpha)
a_float a_lpf_iter(a_lpf *ctx, a_float x)
void a_lpf_zero(a_lpf *ctx)