public class Triangle { /*@ @ requires n >= 0; @ ensures 2 * \result == n * (n+1); @*/ /*@pure@*/ int triangle(int n) { return n == 0 ? 0 : n + triangle(n-1); } /*@ @ requires n >= 0; @ ensures n == 42; @*/ /*@pure@*/ int conundrum(int n) { return conundrum(n) + 1; } }