kinesis4cats.compat.retry.Fibonacci.scala Maven / Gradle / Ivy
/*
* Copyright 2023-2023 etspaceman
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package kinesis4cats.compat.retry
private[kinesis4cats] object Fibonacci {
def fibonacci(n: Int): Long =
if (n > 0)
fib(n)._1
else
0
// "Fast doubling" Fibonacci algorithm.
// See e.g. http://funloop.org/post/2017-04-14-computing-fibonacci-numbers.html for explanation.
private def fib(n: Int): (Long, Long) = n match {
case 0 => (0, 1)
case m =>
val (a, b) = fib(m / 2)
val c = a * (b * 2 - a)
val d = a * a + b * b
if (n % 2 == 0)
(c, d)
else
(d, c + d)
}
}