练习2.13 不用库函数，写一个高效计算ln N的C函数

代码

#include  double MYLOG(double a) { int N = 15; int k,nk; double x,xx,y; x = (a-1)/(a+1); xx = x*x; nk = 2*N+1; y = 1.0/nk; for(k=N;k>0;k--) { nk = nk - 2; y = 1.0/nk+xx*y; } return 2.0*x*y; } int main() { int N=100; for(int a=1;a<N;a++) printf("ln %d = %.10f \n",a,MYLOG(a)); getchar(); return 0; }