21 lines
376 B
C++
21 lines
376 B
C++
#include "nr.h"
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DP NR::trapzd(DP func(const DP), const DP a, const DP b, const int n)
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{
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DP x,tnm,sum,del;
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static DP s;
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int it,j;
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if (n == 1) {
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return (s=0.5*(b-a)*(func(a)+func(b)));
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} else {
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for (it=1,j=1;j<n-1;j++) it <<= 1;
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tnm=it;
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del=(b-a)/tnm;
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x=a+0.5*del;
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for (sum=0.0,j=0;j<it;j++,x+=del) sum += func(x);
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s=0.5*(s+(b-a)*sum/tnm);
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return s;
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}
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}
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