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  1. # Temporarily modify variable and execute within updated environment.
  2.  
  3. from time import process_time
  4.  
  5. # Class for dynamic binding of a variable.
  6.  
  7. class Parameter:
  8.     def __init__(self, v):
  9.         self.v = v
  10.     def __call__(self):
  11.         return self.v
  12.     def bind(self, v, thunk):
  13.         t = self.v
  14.         self.v = v
  15.         thunk()
  16.         self.v = t
  17.  
  18. # Memo.
  19.  
  20. def setdelayed(m, k, thunk=lambda: None):
  21.     if k not in m:
  22.         m[k] = thunk()
  23.     return m[k]
  24.  
  25. def memo(f, keyfunc=lambda x: x):
  26.     m = {}
  27.     def wrapper(*args):
  28.         return setdelayed(m, keyfunc(args), lambda: f(*args))
  29.     return wrapper
  30.  
  31. # Main.
  32.  
  33. fib = Parameter(lambda n: fib()(n-2) + fib()(n-1) if n > 1 else n)
  34.  
  35. def make_f(f):
  36.     return lambda: fib.bind(f, lambda: print(fib()(30)))
  37.  
  38. def time_f(thunk):
  39.     t = process_time()
  40.     thunk()
  41.     print('Elapsed: {:.6f}s'.format(process_time() - t))
  42.  
  43. time_f(make_f(memo(fib())))
  44. time_f(make_f(fib()))
Success #stdin #stdout 0.59s 14072KB
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832040
Elapsed: 0.000000s
832040
Elapsed: 0.503090s
https://ideone.com/Lwz80P
language:
Python 3 (python  3.12)
created:
7 days ago
visibility:
public

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