text: #include <stdio.h>
  #include <math.h>
  #include <stdbool.h>
  double snippet(double xx) {
          int j=0;
          double x = 0.0;
          double y= 0.0;
          double tmp= 0.0;
          double ser= 0;
          double cof[6]={76.18009172947146,-86.50532032941677, 24.01409824083091,-1.231739572450155,0.1208650973866179e-2, -0.5395239384953e-5};
          x = xx;
          y = x;
          tmp=x+5.5;
          //tmp -= (x+0.5)*log(tmp);
          ser=1.000000000190015;
          for (j=0;j<6;j++)
              ser += cof[j]*++y;
          return -tmp+log(2.5066282746310005*ser/x);
  }