isFibonacci function

bool isFibonacci(
  1. int n
)

Checks if a number is in the Fibonacci sequence.

Example:

print(isFibonacci(8)); // prints: true

Implementation

bool isFibonacci(int n) {
  dynamic x = 5 * n * n;
  return isPerfectSquare(x + 4) || isPerfectSquare(x - 4);
}