27 lines
450 B
C++
27 lines
450 B
C++
#include <cmath>
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#include "nr.h"
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using namespace std;
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void NR::chebft(const DP a, const DP b, Vec_O_DP &c, DP func(const DP))
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{
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const DP PI=3.141592653589793;
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int k,j;
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DP fac,bpa,bma,y,sum;
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int n=c.size();
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Vec_DP f(n);
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bma=0.5*(b-a);
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bpa=0.5*(b+a);
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for (k=0;k<n;k++) {
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y=cos(PI*(k+0.5)/n);
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f[k]=func(y*bma+bpa);
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}
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fac=2.0/n;
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for (j=0;j<n;j++) {
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sum=0.0;
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for (k=0;k<n;k++)
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sum += f[k]*cos(PI*j*(k+0.5)/n);
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c[j]=fac*sum;
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}
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}
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