Numeric.h

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/*
    liban - base function to do usefull things related to simulation and scientific work
    Copyright (C) 1999-2005 Stephane Magnenat <nct@ysagoon.com>
    Copyright (c) 2004-2005 Antoine Beyeler <antoine.beyeler@epfl.ch>
    Copyright (C) 2005 Laboratory of Intelligent Systems, EPFL, Lausanne
    See AUTHORS for details

    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
*/

#ifndef __AN_NUMERIC_H
#define __AN_NUMERIC_H

namespace An
{
    class ExpDecay
    {
    public:
        ExpDecay(double t = 5.0, double delta = 1.0, double init = 0.0)
        {
            tau = t;
            dt = delta;
            value = init;
            syncFactor();
        }
    
        // Operations.
        void add(double f) { value += f; }
        void step() { value *= factor; }
        void step(double thisDt) { setDt(thisDt); step(); }
        double getValueAndStep() { double tmp = getValue(); step(); return tmp; }
        double getValueAndStep(double thisDt) { setDt(thisDt); return getValueAndStep(); }
        
        // Accessors.
        void setTau(double t) { if (t != tau) { tau = t; syncFactor(); } }
        double getTau() const { return tau; }
        void setDt(double delta) { if (delta != dt) { dt = delta; syncFactor(); } }
        double getDt() const { return dt; }
        void setValue(double val) { value = val; }
        double getValue() const { return value; }
        
        // Operators.
        void operator = (double val) { setValue(val); }
        void operator += (double f) { add(f); }
        void operator -= (double f) { add(-f); }
        operator double() const { return getValue(); }
        
    protected:
        double tau; 
        double factor; 
        double value; 
        double dt; 
        
        void syncFactor() { factor = (tau - dt * 0.5) / (tau + dt * 0.5); }
    };
}

#endif

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