BSD 4_3_Tahoe release

[unix-history] / usr / lib / learn / C / L42.1a

#print
Write a function 
	inprod(a,b,n)
that computes the inner product of two integer vectors
a and b which are n items long.  Name the file "inprod.c"
and compile and test it; then type ready.
You may assume that the result and all intermediate
values fit in a 16-bit integer, not usually a safe assumption.
#once #create tzaqc.c
main()
{
	int x[100], y[100];
	int k;
	for(k=0; k<100; k++)
	   {
		x[k] = k%10;
		y[k] = (k*k)%3;
	   }
	if (inprod(x,y,100) != xprod(x,y,100)) return(1);
	return(0);
}
xprod(x,y,n)
  int *x, *y;
{
	int k, sum;
	for(sum=k=0; k<n; k++)
	   sum=+ *x++ * *y++;
	return(sum);
}
#user
cc tzaqc.c inprod.o
a.out
#succeed
/* one way */
inprod(a, b, n)
int *a, *b;
{
	int s;

	s = 0;
	while (n--)
		s += *a++ * *b++;

/* none of the spaces in the line above are necessary but
   would you really want to read
      s+=*a++**b++;
   and try to parse it?  Even clearer than what I have,
   but slower, would be
     for(i=0; i<n; i++)
      s += a[i]*b[i];
*/

	return(s);
}
#log
#next
43.1a 10