/* Problem 5: Write a predicate element_at(X,Y,N) that succeeds if X is the Nth element of list Y. Y is 0-indexed.

NOTE: Don't worry about the error cases: i.e, N greater than the length of Y. */

/* Problem 5 Test: */ %:- element_at(3,[1,2,3],2). % SUCCEED %:- element_at(1,[1,2,3],0). % SUCCEED

%:- element_at(1,[1,2,3],1) -> fail ; true. % FAIL

/* Problem 6: Write a predicate insert_at(E,Y,N,Z) that succeeds if Z is the list Y with E inserted at index N -- Insert X at index N in Y.

NOTE: Don't worry about the error cases: i.e, N greater than the length of Y. */

/* Problem 6 Test: */ %:- insert_at(3,[1,2,3],2,[1,2,3,3]). % SUCCEED %:- insert_at(1,[1,2,3],0,[1,1,2,3]). % SUCCEED %:- insert_at(a,[1,2,3],1,[1,a,2,3]). % SUCCEED

%:- insert_at(1,[1,2,3],0,[1,2,3]) -> fail ; true. % FAIL