5/21/97
Two points per part except as noted.
0. The Lisp function 'max' returns the maximum numeric value in a list, or null if its argument is not a list or is a list without numbers in it. Examples:
(max '(10 109 D 7)) returns 109
(max 'sam) returns nil
a. Recast this in terms of Prolog (this part of your answer contains only an English description, no actual Prolog syntax).
b. Using your answer to part a, restate the two LISP examples above in Prolog.
1. Write a Prolog predicate 'startsalike' which returns true if and only if its argument is a list whose first two elements are the same. For full credit, write this as a single fact (nothing on the right-hand side) with no unused variables.
2. Write a Prolog predicate 'findalike' with two arguments. The first argument is a list. If the list contains two consecutive identical elements, then the predicate is true if and only if the second argument is equal to this repeated element. If there is more than one repeated element, the second argument should be the earliest such value. Examples:
findalike([1,2,3,4,5],X)? no
findalike([1,2,2,3,4,5],Y)? Y=2 yes
findalike([1,2,3,2,4,5],Y)? no
findalike([1,3,3,4,5,5,5,6,6],X)? X=3 yes
findalike([a,s,[1,2,k],[1,2,k],z],W)? W=[1,2,k] yes