[SciPy-user] prime numbers

[Adolph J. Vogel]

On Thursday 23 October 2008 14:28:40 Walter Mudzimbabwe wrote:
> can anybody help me figure out why the following program cannot produce
> primes upto 10.
> --------------------------------------------------
> from scipy import *
>
> def isdivisible(n,listt):
>    for i in range(len(listt)):
>        if (n%listt[i]==0):
>            return 1
>        else:
>            return 0
>
> def primes_upto(m):
>    u=[1,2]
>    for i in range(3,m+1):
At this point your only passing the last element of u, which in this case is 
two.  So in isdivisibile() your only checking to see if it is divisible by 
two. You need to check and see whether or not its divisible by the divisors 
smaller then two as well.

Your code is also very complicated for such an simple task.

def isdivisible(p):
    for d in range(1,p):
	if p % d == 0:
		return False
    return True

primes = []
def prime_upto(m):
    for i in range(3,m+1,2):
	if isdivisible(i): primes.append(i)



-- 
Adolph J. Vogel      BEng(Mech)