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+/* ------------------------- delta ------------------------------------------ */
+/* */
+/* Claculate 1st or 2nd order difference. */
+/* Written by Olaf Matthes (olaf.matthes@gmx.de) */
+/* Inspired by code written by Trond Lossius. */
+/* Get source at http://www.akustische-kunst.org/puredata/maxlib/ */
+/* */
+/* This program is free software; you can redistribute it and/or */
+/* modify it under the terms of the GNU General Public License */
+/* as published by the Free Software Foundation; either version 2 */
+/* of the License, or (at your option) any later version. */
+/* */
+/* This program is distributed in the hope that it will be useful, */
+/* but WITHOUT ANY WARRANTY; without even the implied warranty of */
+/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the */
+/* GNU General Public License for more details. */
+/* */
+/* You should have received a copy of the GNU General Public License */
+/* along with this program; if not, write to the Free Software */
+/* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+/* */
+/* Based on PureData by Miller Puckette and others. */
+/* */
+/* ---------------------------------------------------------------------------- */
+
+#include "m_pd.h"
+#include <stdio.h>
+
+#define MAXSIZE 32
+
+static char *version = "delta v0.1, written by Olaf Matthes <olaf.matthes@gmx.de>";
+
+typedef struct delta
+{
+ t_object x_ob;
+ t_outlet *x_out; /* result */
+ t_int x_order; /* 1st or second order */
+ t_int x_clearflag;
+ t_float x_delta; /* the result */
+
+ t_float x_prev; /* previous value */
+ t_float x_prev2; /* value previous to previous value */
+} t_delta;
+
+static void delta_clear(t_delta *x)
+{
+ if(x->x_order == 2)
+ x->x_clearflag = 2;
+ else
+ x->x_clearflag = 1;
+ x->x_delta = 0;
+}
+
+static void delta_bang(t_delta *x)
+{
+ outlet_float(x->x_out, x->x_delta);
+}
+
+static void delta_float(t_delta *x, t_floatarg f)
+{
+ if(x->x_order != 2) /* first order */
+ {
+ if(x->x_clearflag)
+ {
+ x->x_prev = f;
+ x->x_delta = 0;
+ x->x_clearflag = 0;
+ }
+ else
+ {
+ x->x_delta = f - x->x_prev;
+ x->x_prev = f;
+ }
+ }
+ else
+ {
+ switch(x->x_clearflag)
+ {
+ case 0:
+ x->x_delta = f - 2*x->x_prev + x->x_prev2;
+ x->x_prev2 = x->x_prev;
+ x->x_prev = f;
+ break;
+ case 1:
+ x->x_prev = f;
+ x->x_clearflag--;
+ break;
+ case 2:
+ x->x_prev2 = f;
+ x->x_clearflag--;
+ break;
+ }
+ }
+ delta_bang(x);
+}
+
+static t_class *delta_class;
+
+static void *delta_new(t_floatarg f)
+{
+ int i;
+
+ t_delta *x = (t_delta *)pd_new(delta_class);
+ x->x_out = outlet_new(&x->x_ob, gensym("float"));
+
+ x->x_order = (int)f;
+ if(x->x_order == 2)
+ x->x_clearflag = 2;
+ else
+ x->x_clearflag = 1;
+ x->x_delta = 0;
+
+ return (void *)x;
+}
+
+#ifndef MAXLIB
+void delta_setup(void)
+{
+ delta_class = class_new(gensym("delta"), (t_newmethod)delta_new,
+ 0, sizeof(t_delta), 0, A_DEFFLOAT, 0);
+#else
+void maxlib_delta_setup(void)
+{
+ delta_class = class_new(gensym("maxlib_delta"), (t_newmethod)delta_new,
+ 0, sizeof(t_delta), 0, A_DEFFLOAT, 0);
+#endif
+ class_addfloat(delta_class, delta_float);
+ class_addbang(delta_class, (t_method)delta_bang);
+ class_addmethod(delta_class, (t_method)delta_clear, gensym("clear"), 0);
+ class_sethelpsymbol(delta_class, gensym("maxlib/delta-help.pd"));
+#ifndef MAXLIB
+
+ post(version);
+#else
+ class_addcreator((t_newmethod)delta_new, gensym("delta"), A_DEFFLOAT, 0);
+ class_sethelpsymbol(delta_class, gensym("maxlib/delta-help.pd"));
+#endif
+}
+