Recursive program to compute Taylor approx of cosine not functioning in Prolog

Question

I\'m still pretty new to Prolog, and i\'m not sure why this code isn\'t working. I believe it is most likely a problem with the base case or in the last 3 lines of the recursive

Answer 1

Base case was wrong, should've been cosN(N,N,_,0). as K and N must both be equal to N when the program is finished the recursive process.

Test cases:

:- begin_tests(cosine_approximation).

factorial_test_case_generator(0,1).
factorial_test_case_generator(1,1).
factorial_test_case_generator(2,2).
factorial_test_case_generator(3,6).
factorial_test_case_generator(4,24).
factorial_test_case_generator(5,120).
factorial_test_case_generator(6,720).
factorial_test_case_generator(7,5040).
factorial_test_case_generator(8,40320).
factorial_test_case_generator(20,2432902008176640000).

test('factorial',[nondet,forall(factorial_test_case_generator(N,Factorial))]) :-
    fact(N,Factorial).

signCnt_test_case_generator(0,1).
signCnt_test_case_generator(1,-1).
signCnt_test_case_generator(2,1).
signCnt_test_case_generator(3,-1).
signCnt_test_case_generator(4,1).
signCnt_test_case_generator(5,-1).

test('signCnt',[nondet,forall(signCnt_test_case_generator(N,Sign))]) :-
    signCnt(N,Sign).

cosN_test_case_generator(3,pi/2,0.01996895776487828).
cosN_test_case_generator(5,pi,-0.9760222126236076).
cosN_test_case_generator(25,pi,-1.0).
cosN_test_case_generator(10,pi/2,-3.3306690738754696e-15).

test('cosN',[nondet,forall(cosN_test_case_generator(N,X,Y))]) :-
    cosN(N,X,Y).

:- end_tests(cosine_approximation).

Example run:

?- make.
% /Users/oliverclarke/prolog/lab5-quiz compiled 0.00 sec, 3 clauses
% PL-Unit: cosine_approximation .................... done
% All 20 tests passed
true.