CSCI 3675
Fall 2000
Exercise Set 2
Due: Wednesday, September 20.
- 6.1. Using equations (6.5.1), show an inside-out evaluation
of expression pow(2,5). [In the old notes, that will be in Chapter
5, the definition of pow.]
- 6.3. Write an equational definition of digitsum, where
digitsum(n) is the sum of the digits in decimal number n. For
example, digitsum(554) = 5 + 5 + 4 = 14.
- 7.2. Show an inside-out evaluation of expression
take(2, [4,3,2]).
- 7.5. Write an equational definition of function ziplist,
where ziplist([a,b,c,d], [u,v,w,x]) = [[a,u], [b,v], [c,w], [d,x]].
In general, ziplist takes a list of pairs and produces a pair of lists.
(The analogy is with the action of a zipper.) Assume that the
two lists have the same length. Do not worry about what happens
if they have different lengths.
- 7.7. Write an equational definition of function positives(x)
that produces a list of the positive members of list x. For
example, positives([2,-6,-1,4,0]) = [2,4].