奇异点的高斯积分c++程序

奇异点的高斯积分c++程序

#include
#include
#define N 3
float gauss(float(*)(float), float, float, int);
void main( )
{
float function_name(float);
float a, b;
printf ("请输入积分上限b\n");
scanf("%f", &b);
printf("请输入积分下限a\n");
scanf("%f", &a);
float ans;
ans=gauss(function_name, a, b, N);
printf("ans=%f", ans);
}

float gauss(float(*func)(float x), float a, float b, int n )
{

float x1[1]={0.0};
float A1[1]={2};
float x2[2]={-0.5573503, 0.5573503};
float A2[2]={1, 1};
float x3[3]={-0.7745967, 0.0, 0.7745967};
float A3[3]={0.555556, 0.888889, 0.555556};
float x4[4]={0.3399810, -0.3399810, 0.8611363, -0.8611363};
float A4[4]={0.6521452, 0.6521452, 0.3478548, 0.3478548};
float x5[5]={0.0, 0.5384693, -0.5384693, 0.9061799, -0.9061799};
float A5[5]={0.5688889, 0.4786287, 0.4786287, 0.2369269, 0.2369269};
float *p, *t;
switch (n)
{
case 1:
p=x1;
t=A1;
break;
case 2:
p=x2;
t=A2;
break;
case 3:
p=x3;
t=A3;
break;
case 4:
p=x4;
t=A4;
break;
case 5:
p=x5;
t=A5;
break;
default:
printf ("intput wrong!");
}
float g;
int i;
for (i=0,g=0; ig+=(*func)((b-a)*p[i]/2+(a+b)/2)*t[i];
}
g*=(b-a)/2;
return g;
}
float function_name(float x)
{
return (sqrt(4-x*x));
}

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