3 * Copyright 2002 Free Software Foundation, Inc.
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22 #ifndef _GR_SINGLE_ZERO_REC_H_
23 #define _GR_SINGLE_ZERO_REC_H_
28 * \brief class template for single zero recursive filter
30 template<class o_type, class i_type, class tap_type>
31 class gr_single_zero_rec {
34 * \brief construct new single zero IIR with given alpha
36 * computes y(i) = alpha * x(i) - (1-alpha) * y(i-1)
38 gr_single_zero_rec (tap_type alpha = 1.0)
45 * \brief compute a single output value.
46 * \returns the filtered input value.
48 o_type filter (const i_type input);
51 * \brief compute an array of N output values.
52 * \p input must have n valid entries.
54 void filterN (o_type output[], const i_type input[], unsigned long n);
57 * \brief install \p alpha as the current taps.
59 void set_taps (tap_type alpha)
61 if (alpha < 0 || alpha > 1)
62 throw std::out_of_range ("Alpha must be in [0, 1]\n");
65 d_one_minus_alpha = 1.0 - alpha;
68 //! reset state to zero
74 tap_type prev_output () { return d_prev_output; }
78 tap_type d_one_minus_alpha;
79 tap_type d_prev_output;
84 // general case. We may want to specialize this
86 template<class o_type, class i_type, class tap_type>
88 gr_single_zero_rec<o_type, i_type, tap_type>::filter (const i_type input)
92 output = d_alpha * input - d_one_minus_alpha * d_prev_output;
93 d_prev_output = output;
95 return (o_type) output;
99 template<class o_type, class i_type, class tap_type>
101 gr_single_zero_rec<o_type, i_type, tap_type>::filterN (o_type output[],
102 const i_type input[],
105 for (unsigned i = 0; i < n; i++)
106 output[i] = filter (input[i]);
110 #endif /* _GR_SINGLE_ZERO_REC_H_ */