Exercises on Section 5

Give a full description of a function (using the infix notation ×) corresponding to multiplication of integers.

With n = 966, evaluate each of:

(a) MOD(n, 10);

(b) DIV (n, 10);

(c) MOD(DIV (n, 10), 10).

The function LAST is described below.

function LAST(s in SeqOfX ) return in X

pre   s is not empty.

post   The returned value is the last element in s. For example, LAST([1, 2, 3]) = 3.

Consider the expression NOT(LAST(s) = _Char LAST (t)).

• (a) What is the value of this expression if s is “the” and t is:

  • (i) “same”;

  • (ii) “different”?

• (b) Under what circumstances does this expression have the value true?

• (c) Is this expression valid with s = [1,2] and t = [1,8,4,2]?