
void chder(a,b,c,cder,n)
double a,b,c[],cder[]; /* c[] and cder[] must not overlap */
int n;
{
        register int j;
        register double con,cj1,cdj2,cdj1,cdj;
        con = 2/(b-a);
        cdj1 = 2*(n-1)*c[n-1];
        cj1 = 2*(n-2)*c[n-2];
        cder[n-1] = cdj2 = 0;
        for(j = n-2; --j >= 0;){
                cdj = cdj2+cj1; /* the recursive result of first loop */
                cj1 = 2*j*c[j]; /* prefetch for next loop iteration */
                cder[j+1] = con*(cdj2=cdj1); /* complete final loop */
                cdj1 = cdj; /* compiler doesn't worry about aliasing of locals */
        }
        cder[0] = con*cdj1;
}

