On Wednesday, April 15, 2015 at 8:07:31 AM UTC+5:30, Paul Rubin wrote:
> Steven D'Aprano writes:
> > primes = sieve [2..]
> > sieve (p : xs) = p : sieve [x | x <- xs, x `mod` p > 0]
> > In her paper http://www.cs.hmc.edu/~oneill/papers/Sieve-JFP.pdf, Melissa
> > O'Neill calls this the "Sleight on Eratosthenes".
>
> Oh cool, I wrote very similar Haskell code and converted it to Python.
> I probably saw it before though, so it looks like a case of
> not-exactly-independent re-invention.
>
> > def turner():
> > nums = itertools.count(2)
> > while True:
> > prime = next(nums)
> > yield prime
> > nums = filter(lambda v, p=prime: (v % p) != 0, nums)
Here's a massive parallel (and more massively inefficient)
Turner sieve as bash script
$ cat nos2
n=2
while true ; do
echo $n
n=$(($n + 1))
done
$ cat filt
read x
while true ; do
if [ $(($x % $1)) -ne 0 ] ; then
echo $x
fi
read x
done
$ cat sieve
read x
echo $x
filt $x | sieve
Call as
nos2|sieve|less
For 1st ten primes
$ nos2|sieve |head
2
3
5
7
11
13
17
19
23
29
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