from a cimport *
cdef extern from "a/hpf.h":
ctypedef struct a_hpf:
a_float alpha
a_float output
a_float input
a_float a_hpf_gen(a_float fc, a_float ts)
void a_hpf_init(a_hpf *ctx, a_float alpha)
a_float a_hpf_iter(a_hpf *ctx, a_float x)
void a_hpf_zero(a_hpf *ctx)