Do the following exercises from Chapter 21 on paper: Exercises 21.1-3,9.
As mentioned in the textbook, arithmetic is not well integrated into
Prolog. Suppose < and other relation operators were fully
invertible predicates that would work on variables (assuming integers
only for now):
?- X>2, X<5. X = 3; X = 4 YesSuppose further, there was a predicate
eval that would evaluate
arithmetic terms, which would work even with variables:
?- eval(X*X+1,5). X = 2; X = -2 Yes ?- eval(X,2). X = 2; X = 0+2; % many, many more solutions YesWrite (on paper) the definition of
eval that can handle
arbitrary expressions involving addition and multiplication with
variables and constants. Your definition may use (unimplemented) predicates
add(_,_,_), mul(_,_,_), and isNum(_).
Why do you think Prolog does not do things this way?
Hint: think about how add(_,_,_) and isNum(_) would be
implemented and how they would work. Your discussion should include
information on the cost model for these (hypothetical) predicates.
Do Exercises 22.2 and 22.8. Put the results in optimize.pl;
your solution will use subseq and minlist (analogous to
your answer to 22.2). It is permitted to return the same (optimal)
cover more than once.
You submit your program work by putting it in the homework11 directory
in your AFS class volume.
You may do all your work in this directory, or you may wish to do your
work in a different directory and copy things when correct into this
directory. In any case, you will lose permission to write things in
this directory after the deadline, which is 4:00pm on Tuesday,
April 27. In other words, you must be done before lecture
starts.
The homework11 directory should include the following:
optimize.pl