30 lines
454 B
C
30 lines
454 B
C
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#include <math.h>
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#include "nrutil.h"
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#define PI 3.141592653589793
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void chebft(a,b,c,n,func)
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float (*func)(),a,b,c[];
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int n;
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{
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int k,j;
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float fac,bpa,bma,*f;
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f=vector(0,n-1);
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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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float 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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double 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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free_vector(f,0,n-1);
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}
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#undef PI
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