double polint3(double x, int n, double *xa, double *ya)
{ int shift=leftX(n, xa, x);
double ar;
ar=polintN(x,3,xa+shift, ya+shift);
if(shift==0) return ar;
shift--;
return 0.5*( ar+ polintN(x,3,xa+shift, ya+shift));
}
static double polint4(double x, int n, double *xa, double *ya)
{ int shift=leftX4(n, xa, x);
return polintN(x,4,xa+shift, ya+shift);
}
double polint2(double x, int n, double *xa, double *ya)
{ int shift=leftXN(2,n, xa, x);
return polintN(x,2,xa+shift, ya+shift);
}
