## C++, math, fibonacci.cpp

/**
* @file
* @brief Generate fibonacci sequence
*
* Calculate the the value on Fibonacci's sequence given an
* integer as input.
* \f[\text{fib}(n) = \text{fib}(n-1) + \text{fib}(n-2)\f]
*
* @see fibonacci_large.cpp, fibonacci_fast.cpp, string_fibonacci.cpp
*/
#include <cassert>
#include <iostream>

/**
* Recursively compute sequences
* @param n input
* @returns n-th element of the Fbinacci's sequence
*/
uint64_t fibonacci(uint64_t n) {
/* If the input is 0 or 1 just return the same
This will set the first 2 values of the sequence */
if (n <= 1) {
return n;
}

/* Add the last 2 values of the sequence to get next */
return fibonacci(n - 1) + fibonacci(n - 2);
}

/**
* Function for testing the fibonacci() function with a few
* test cases and assert statement.
* @returns void
*/
static void test() {
uint64_t test_case_1 = fibonacci(0);
assert(test_case_1 == 0);
std::cout << "Passed Test 1!" << std::endl;

uint64_t test_case_2 = fibonacci(1);
assert(test_case_2 == 1);
std::cout << "Passed Test 2!" << std::endl;

uint64_t test_case_3 = fibonacci(2);
assert(test_case_3 == 1);
std::cout << "Passed Test 3!" << std::endl;

uint64_t test_case_4 = fibonacci(3);
assert(test_case_4 == 2);
std::cout << "Passed Test 4!" << std::endl;

uint64_t test_case_5 = fibonacci(4);
assert(test_case_5 == 3);
std::cout << "Passed Test 5!" << std::endl;

uint64_t test_case_6 = fibonacci(15);
assert(test_case_6 == 610);
std::cout << "Passed Test 6!" << std::endl << std::endl;
}

/// Main function
int main() {
test();
int n = 0;
std::cin >> n;
assert(n >= 0);
std::cout << "F(" << n << ")= " << fibonacci(n) << std::endl;
}