double dot(a,na,b,nb,n)/* dot product a and b, na is a increment, mb is b increment */register double *a,*b;register int na,nb,n;{	register int i;	register double sum;	sum=0;	for(i=0;i<n;i++,a+=na,b+=nb)		sum+=(*a)*(*b);	return(sum);}