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Annotation of 42BSD/usr.lib/learn/C/L42.1a, revision 1.1.1.1

1.1       root        1: #print
                      2: Write a function 
                      3:        inprod(a,b,n)
                      4: that computes the inner product of two integer vectors
                      5: a and b which are n items long.  Name the file "inprod.c"
                      6: and compile and test it; then type ready.
                      7: You may assume that the result and all intermediate
                      8: values fit in a 16-bit integer, not usually a safe assumption.
                      9: #once #create tzaqc.c
                     10: main()
                     11: {
                     12:        int x[100], y[100];
                     13:        int k;
                     14:        for(k=0; k<100; k++)
                     15:           {
                     16:                x[k] = k%10;
                     17:                y[k] = (k*k)%3;
                     18:           }
                     19:        if (inprod(x,y,100) != xprod(x,y,100)) return(1);
                     20:        return(0);
                     21: }
                     22: xprod(x,y,n)
                     23:   int *x, *y;
                     24: {
                     25:        int k, sum;
                     26:        for(sum=k=0; k<n; k++)
                     27:           sum=+ *x++ * *y++;
                     28:        return(sum);
                     29: }
                     30: #user
                     31: cc tzaqc.c inprod.o
                     32: a.out
                     33: #succeed
                     34: /* one way */
                     35: inprod(a, b, n)
                     36: int *a, *b;
                     37: {
                     38:        int s;
                     39: 
                     40:        s = 0;
                     41:        while (n--)
                     42:                s += *a++ * *b++;
                     43: 
                     44: /* none of the spaces in the line above are necessary but
                     45:    would you really want to read
                     46:       s+=*a++**b++;
                     47:    and try to parse it?  Even clearer than what I have,
                     48:    but slower, would be
                     49:      for(i=0; i<n; i++)
                     50:       s += a[i]*b[i];
                     51: */
                     52: 
                     53:        return(s);
                     54: }
                     55: #log
                     56: #next
                     57: 43.1a 10

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