[Python-ideas] Add the imath module

[Serhiy Storchaka]

12.07.18 15:15, David Mertz пише:
> On Thu, Jul 12, 2018, 7:56 AM Serhiy Storchaka 
> <storchaka at gmail.com 
> <mailto:storchaka at gmail.com>> wrote:
> 
>     * isprime(n)
>     Tests if n is a prime number.
> 
> 
> How would you test this? The Miller-Rabin Primality test? For large 
> numbers, iterating through candidate prime divisors is pricey.
> 
>     * primes()
>     Returns an iterator of prime numbers: 2, 3, 5, 7, 11, 13,...
> 
> 
> How would you implements this? Sieve of Eratosthenes is really fun to 
> show students as a Python generator function. But the cached primes DO 
> grow unboundedly as you utilize the generator. Wheel factorization as 
> first pass? Do you cached the first N primes so the each instance of 
> iterator can provide initial elements much faster? What is N?

I didn't mean any concrete implementation. Sure there are enough 
efficient and simple. I sometimes need a sequence of prime numbers for 
solving toy problems, and quickly write something like:

def primes(n):
     return (i for i in range(2, n) if all(i % j for j in 
primes(int(sqrt(i)) + 1)))

Having such feature in the stdlib would be very convenient. Any 
reasonable implementation is enough efficient for my purposes.