試題詳解

18. Ackermann's function is an example of a recursive function which is not primitive recursive. It is interesting from the point of view of benchmarking because it "grows faster than any primitive recursive function." Ackermann's function is defined as follows: A(0,n)=n+1
A(m,0)=A(m-1,1)
A(m,n)=A(m-1,A(m,n-1))
What is the A(1,3) return value of the following program?

(A) 2
(B) 3
(C) 4
(D) 5
(E) 6