1#! /usr/bin/env python
2
3# Print digits of pi forever.
4#
5# The algorithm, using Python's 'long' integers ("bignums"), works
6# with continued fractions, and was conceived by Lambert Meertens.
7#
8# See also the ABC Programmer's Handbook, by Geurts, Meertens & Pemberton,
9# published by Prentice-Hall (UK) Ltd., 1990.
10
11import sys
12
13def main():
14    k, a, b, a1, b1 = 2, 4, 1, 12, 4
15    while True:
16        # Next approximation
17        p, q, k = k*k, 2*k+1, k+1
18        a, b, a1, b1 = a1, b1, p*a+q*a1, p*b+q*b1
19        # Print common digits
20        d, d1 = a//b, a1//b1
21        while d == d1:
22            output(d)
23            a, a1 = 10*(a%b), 10*(a1%b1)
24            d, d1 = a//b, a1//b1
25
26def output(d):
27    # Use write() to avoid spaces between the digits
28    sys.stdout.write(str(d))
29    # Flush so the output is seen immediately
30    sys.stdout.flush()
31
32if __name__ == "__main__":
33    main()
34