[Edu-sig] generate digits of pi

[Litvin]

Or just replace

         while d == d1:
with
         while d == d1 and n > 0:

Gary Litvin
www.skylit.com

At 11:54 PM 12/23/2012, david at handysoftware.com wrote:

>Here's an easier, pythonic way to limit the number of digits, given 
>the original, non-terminating pi generator:
>
> >>> import itertools
> >>> print(list( itertools.islice(pi_digits(), 10) ))
>[3, 1, 4, 1, 5, 9, 2, 6, 5, 3]
>
>
>
>David H
>
>
>
>-----Original Message-----
>From: "michel paul" <pythonic.math at gmail.com>
>Sent: Sunday, December 23, 2012 6:49pm
>To: "Kirby Urner" <kurner at oreillyschool.com>
>Cc: david at handysoftware.com, "edu-sig at python.org" 
><edu-sig at python.org>, "michel paul" <pythonic.math at gmail.com>
>Subject: Re: [Edu-sig] generate digits of pi
>
>I realized something. This was the original version:
>
>def pi_digits():
>k, a, b, a1, b1 = 2, 4, 1, 12, 4
>while True:
>p, q, k = k*k, 2*k+1, k+1
>a, b, a1, b1 = a1, b1, p*a+q*a1, p*b+q*b1
>d, d1 = a/b, a1/b1
>while d == d1:
>yield int(d)
>a, a1 = 10*(a%b), 10*(a1%b1)
>d, d1 = a/b, a1/b1
>
>I forget where it came from. Like I had mentioned, I had a really 
>bright student awhile back who was really intrigued by this, and he 
>at one point edited it to produce the digits in binary. In the 
>original form the generator never terminates. Somewhere along the 
>line an edit was made to try to get it to terminate at n digits. 
>Probably to make calling it easy to call as in list(pi_digits(n)).
>- Michel
>
>
>On Sat, Dec 22, 2012 at 5:34 PM, Kirby Urner 
><<mailto:kurner at oreillyschool.com>kurner at oreillyschool.com> wrote:
>Got it, no wrong digits just not always exactly the number you asked for.
>
>This happens often in 3.2 as well:
>
> >>> exp = ((n,len(list(pi_digits(n)))) for n in range(10000))  # 
> (number asked, number got)
> >>> exp2 = ((a,b) for a,b in exp if a != b)  # filter on "not same"
> >>> for i in range(10): print(next(exp2), end=", ")
>(2, 3), (4, 5), (10, 11), (16, 17), (18, 19), (22, 23), (28, 31), 
>(29, 31), (30, 31), (34, 36),
>
>Kirby
>
>
>
>On Sat, Dec 22, 2012 at 4:40 PM, 
><<mailto:david at handysoftware.com>david at handysoftware.com> wrote:
>
>In each case I asked for only 79 digits, but got 79, 82, and 83 
>digits depending on whether I was using python 3.2, python 2.6, or 
>python 2.6 with -Qnew, respectively. The digits all seem to be 
>correct, but the algorithm for stopping at digit n seems to be very sensitive.
>
>
>
>David H
>
>
>
>
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>==================================
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>==================================
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