fib.C

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
 
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/
 
 
# include <cstdlib>
# include <iostream>
# include <tpl_arrayStack.H>
 
using namespace std;
using namespace Aleph;
 
int fib_it(int n)
{
  if (n <= 1)
    return 1;
 
  int fi_1 = 1, fi_2 = 1, fi = 0, i;
 
  for (i = 2; i <= n; i++, fi_2 = fi_1, fi_1 = fi)
    fi = fi_1 + fi_2;
 
  return fi;
}
 
int fib_rec(int n)
{
  if (n <= 1)
    return 1;
 
  int f1 = fib_rec(n - 1);
  int f2 = fib_rec(n - 2);
  return f1 + f2;
}
 
 
# define P0 0
# define P1 1
# define P2 2
 
struct Item
{
  int n;
  int f1;
  int result;
  char return_point;
};
 
# define N  (stack.top().n)
# define F1 (stack.top().f1)
# define RESULT (stack.top().result)
# define RETURN_POINT (stack.top().return_point)
 
int fib_st(int n)
{
  ArrayStack<Item> stack;
  Item first_activation_register;
  Item current_activation_register;
 
  first_activation_register.n = n;
 
  stack.push(first_activation_register);
 
  while (1)
    {
      if (N <= 1)
  {
    current_activation_register = stack.pop();
    current_activation_register.result = 1;
    stack.push(current_activation_register);
    goto exit_from_fib;
  }
 
      { /* Esta es la llamada a fib(n - 1) */
  Item new_activation_register;
  new_activation_register.n     = N - 1;
  new_activation_register.return_point = P1;
  stack.push(new_activation_register);
  continue;
      }
 
    p1: /* Esta es la salida de fib(n - 1) */
      current_activation_register = stack.pop();
      current_activation_register.f1 = current_activation_register.result; /* int f1 = fib(n - 1) */
      stack.push(current_activation_register);
 
      { /* Esta es la llamada a fib(n - 2) */
  Item new_activation_register;
  new_activation_register.n = N - 2;
  new_activation_register.return_point = P2;
  stack.push(new_activation_register);
  continue;
      }
 
    p2: /* Esta es la salida de fib(n - 2) */
      current_activation_register = stack.pop();
      current_activation_register.result =
  current_activation_register.f1 + current_activation_register.result;
      stack.push(current_activation_register);
 
    exit_from_fib:
      if (stack.size() == 1)
  return RESULT;
 
      current_activation_register = stack.pop();
      char return_point = current_activation_register.return_point;
 
      // Propagate result to caller
      int res = current_activation_register.result;
      Item caller = stack.pop();
      caller.result = res;
      stack.push(caller);
 
      switch (return_point)
  {
  case P1: goto p1;
  case P2: goto p2;
  }
    }
}
 
 
 
int main(int argc, char * argv[])
{
  int n = 10;
  if (argc > 1)
    {
      try { n = std::stoi(argv[1]); }
      catch (const std::exception& e) 
  { 
    std::cerr << "Warning: could not parse n, using default n=10" << std::endl;
    n = 10; 
  }
    }
 
  if (n < 0)
    {
      std::cerr << "n must be non-negative" << std::endl;
      return 1;
    }
 
  cout << "fib(" << n << ") = " << fib_rec(n) << " = " << fib_it(n)
       << " = " << fib_st(n) << endl;
}