From: mfb@mbunix.mitre.org (Michael F Brenner)
Subject: Re: Prime Number Algorithm Needed
Date: 1997/11/22
Date: 1997-11-22T00:00:00+00:00 [thread overview]
Message-ID: <657i4v$p6h@top.mitre.org> (raw)
In-Reply-To: 6548v3$ocm$1@news1.bu.edu
Prime numbers are intricately related to Mathematical Group Theory.
If G is a finite Group with order (G) equal to a prime number
then G is a cyclic group. However, this implication is not two-way,
so we cannot depend on a loop like the following:
G:=create_cyclic_group(PRIME);
loop
PRIME := PRIME + 1;
loop
H := create_group (with_order => PRIME);
if cyclic(H) then raise found_the_next_prime_number; end if;
exit when no_more_groups_of_this_order;
end loop;
end loop;
However, we also have Fermat's Theorem that if N is a prime number
and I is any integer, then I**N is congruent to I modulo N. That can
lead to the following loop.
N:=get_prime_number_from User;
assert (prime (N));
loop
n:=n+1;
exit when check_all_integers (against_prime_number => N);
end loop;
text_io.put_line ("the next prime is " & integer'image (N));
Either of these two ways gives you something to think about. So, Happy
Thinksgiving :)
next prev parent reply other threads:[~1997-11-22 0:00 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
1997-11-21 0:00 Prime Number Algorithm Needed Thomas Dauria
1997-11-22 0:00 ` Michael F Brenner [this message]
1997-11-22 0:00 ` Geert Bosch
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