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