- by HH
#!/usr/bin/python
#
# Description: bitwise factorization and then trying to find
# an elegant way to print numbers
# Source: http://forums.xkcd.com/viewtopic.php?f=11&t=61300#p2195422
# bug with large numbers such as 99, but main point in simplifying it
#
def primes(n):
# all even numbers greater than 2 are not prime.
s = [False]*2 + [True]*2 + [False,True]*((n-4)//2) + [False]*(n%2)
i = 3;
while i*i < n:
# get rid of ** and skip even numbers.
s[i*i : n : i*2] = [False]*(1+(n-i*i)//(i*2))
i += 2
# skip non-primes
while not s[i]: i += 2
return s
# TRIAL: can you find a simpler way to print them?
# feeling the overuse of assignments but cannot see a way to get it simpler
#
p = 49
boolPrimes = primes(p)
numbs = range(len(boolPrimes))
mydict = dict(zip(numbs, boolPrimes))
print([numb for numb in numbs if mydict[numb]])
Something I am looking for, can you get TRIAL to be of the extreme simplicity below? Any such method?
a=[True, False, True]
b=[1,2,3]
b_a # any such simple way to get it evaluated to [1,3]
# above a crude way to do it in TRIAL
