Created
November 24, 2014 13:27
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Infinite prime number list
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class Prime: | |
def __init__(self): | |
self.found = [] | |
self.i = 2 | |
self.idx = -1 #Iterator用 | |
def __getitem__(self, n): #n番目の素数が見つかるまでwhileを回す | |
while len(self.found) < n+1: #すでに見つかっていれば定数時間ですむ | |
if not any(self.i % x == 0 for x in self.found): | |
self.found.append(self.i) | |
self.i += 1 | |
return self.found[n] | |
def __iter__(self): #ループのためにイテレータとして参照された場合 | |
self.idx = -1 | |
return self | |
def __len__(self): #無限という建前なので長さはない | |
return None | |
def __next__(self): #__next__ (Python 2ならnext) でイテレータにもなれる | |
self.idx += 1 | |
return self.__getitem__(self.idx) #idx番目の素数を返すだけ | |
p = Prime() | |
for i in range(10): #添字表現による参照 | |
print('Prime number #%d = %d' % (i+1, p[i])) | |
for n in p: #Iteratorによるループ(無限に回るので途中で打ち切る必要がある) | |
print('n = ', n) | |
if n > 50: break |
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