using System;
using System.Collections.Generic;
 
namespace Articulos.Cap04.Iteradores
{
    public sealed class IteradorSerieFibonacci
    {
        public static void Main()
        {
            // El iterador se encarga de recorrer cada elemento 
            // generado por el método `Fibonacci`:
            foreach (int fib in Fibonacci(7))
            {
                Console.Write ("{0} ", fib.ToString() );
            }
 
            Console.WriteLine ();
        }
 
        // Retorna elemento por elemento de la serie Fibonacci 
        // hasta la cantidad especificada en el argumento:
        private static IEnumerable<int> Fibonacci(int numero)
        {
            // Por cada iteración retorna el valor de la serie actual, 
            // realiza los cálculos necesarios para generar el siguiente 
            // valor de la serie:
            for (int i = 0, fibAnterior = 1, fibActual = 1; i < numero; ++i)
            {
                // Retorna el valor actual de la serie Fibonacci:
                yield return fibAnterior;
 
                int fibNuevo = fibAnterior + fibActual;
 
                fibAnterior = fibActual;
                fibActual = fibNuevo;
            }
        }
    }
}

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