gistfile1.txt

# Forgets results in between calls
# Also, it is nowhere close to as efficient as the Haskell version
# i.e. I think this is exponential in time
def fibs_gen():
    yield 0
    yield 1
    
    fib = fibs_gen()
    
    fib_tail = fibs_gen()
    next(fib_tail)
    
    for i, j in zip(fib, fib_tail):
        yield i + j

for i, x in enumerate(fibs_gen()):
    if i >= 100:
        break
    print(x)

# Psuedo-Infinite List
# Remembers middle results between function calls
# Uses array, not linked list representation
# Not recursive
class Fib:
    _fibs = [0, 1]
    def __getitem__(self, index):
        for i in range(len(self._fibs), index + 1):
            self._fibs.append(self._fibs[i - 1] + self._fibs[i - 2])
        return self._fibs[index]
fibs = Fib()

print(fibs[100])


# Psuedo-Infinite List
# Remembers middle results between function calls
# Uses array, not linked list representation
# Recursive
# Closest Python version to the Haskell code
class FibRec:
    _fibs = [0, 1]
    def __getitem__(self, index):
        if index >= len(self._fibs):
            self._fibs.append(self[index - 1] + self[index - 2])
        return self._fibs[index]
fibs_rec = FibRec()

print(fibs_rec[56])