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5-19.c
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C/C++ Source or Header
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1991-12-04
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/* Copyright (c) 1992 by AT&T Bell Laboratories. */
/* Advanced C++ Programming Styles and Idioms */
/* James O. Coplien */
/* All rights reserved. */
#include <complex.h>
typedef double time;
class SeriesRLCStepResponse {
public:
virtual complex current(time t) { return object->current(t); };
double frequency() const { return 1.0 / (L * C); }
SeriesRLCStepResponse(double r, double l,
double c, double initialCurrent, short isenvelope=1);
protected:
double R, L, C, currentT0;
double alpha;
complex omegad, a1, b1, a2, b2, s1, s2;
private:
SeriesRLCStepResponse *object;
};
class UnderDampedResponse: public SeriesRLCStepResponse {
public:
UnderDampedResponse(double r, double l, double c, double i) :
SeriesRLCStepResponse(r,l,c,i,0) { }
complex current(time t) {
return exp(-alpha * t) * (b1 * cos(omegad * t) +
b2 * sin(omegad * t));
}
};
class OverDampedResponse: public SeriesRLCStepResponse {
public:
OverDampedResponse(double r, double l, double c, double i) :
SeriesRLCStepResponse(r,l,c,i,0) { }
complex current(time t) {
return a1 * exp(s1 * t) + a2 * exp(s2 * t);
}
};
class CriticallyDampedResponse: public SeriesRLCStepResponse {
public:
CriticallyDampedResponse(double r, double l, double c, double i) :
SeriesRLCStepResponse(r,l,c,i,0) { }
complex criticallyDampedResponse(time t) {
return exp(-alpha * t) * (a1 * t + a2);
}
};
SeriesRLCStepResponse::SeriesRLCStepResponse(
double r, double l, double c, double initialCurrent,
short isenvelope) {
R = r; L = l; C = c; currentT0 = initialCurrent;
alpha = R / (L + L);
// calculation of a1, b1, a2, b2, etc
if (isenvelope) {
if (alpha < frequency()) {
object = new UnderDampedResponse(r, l, c, initialCurrent);
} else if (alpha > frequency()) {
object = new OverDampedResponse(r, l, c, initialCurrent);
} else {
object = new CriticallyDampedResponse(r, l, c, initialCurrent);
}
} else {
omegad = sqrt(frequency() * frequency() - alpha * alpha);
}
}
int main() {
SeriesRLCStepResponse afilter(0.0, 0.0, 0.0, 0.0);
complex i10 = afilter.current(10.0);
}