is prime

[MisterX]

Simon said (gut pun!)

> Is there a function or command to tell me if a selected line 
> of a fld is a prime number?  For example, a user selects line 
> 3 of a fld, I'd like a true or false result to appear in the 
> message box if that number is prime or not.  Or do I need to 
> write a little function myself as no such feature exists?

Courtesy of http://MonsieurX.com - Free nitrous for RunRev 
Naturally, you're encouraged to donate something to our
paypal icon...

Here's a script I wrote and rewrite quite a bit over and 
over but which may not be totally optimized but which is
quite fast and precise (not all prime finding functions are
exact!)... The only limit to this program is the size handled
by X in the IDE. In runrev, that's (2^32)-1 or (2^63)-1

Im waiting for a program to tell me if a 600MB ascii 
sized integer number is a prime since 5 months!

 function isPrime x
  if last char of x is in "0,5,2,4,6,8" then
    return false
  end if
   
  if x>3 and sumdigits(x) mod 3 = 0 then
    return false
  end if
  if x>17 and x mod 17 = 0 then 
    return false
  end if
  if x>7 and x mod 7 = 0 then
    return false
  end if
  
  if x > 11 and x mod 11 = 0 then 
    return false
  end if
   
  put (x div 2) into xfactors
  
  repeat with c = 2 to xfactors
    if last char of c is in "246805" then next repeat
    if x mod 3 > 0 then next repeat
    if x div c = 0 then
      return false
    end if
  end repeat
  return true
end isprime

function sumdigits x
  local z=0
  repeat for each char c in x
    add c to z
  end repeat
  return z
end sumdigits

A download is coming soon to MonsieurX.com... I guess i'll have to 
make a nice little gui for my primes finder stack after all... ;)

cheers
Xavier

> -----Original Message-----
> From: metacard-bounces at lists.runrev.com 
> [mailto:metacard-bounces at lists.runrev.com] On Behalf Of Simon Lord
> Sent: Wednesday, December 08, 2004 19:18
> To: MetaCard
> Subject: is prime
> 
> Is there a function or command to tell me if a selected line 
> of a fld is a prime number?  For example, a user selects line 
> 3 of a fld, I'd like a true or false result to appear in the 
> message box if that number is prime or not.  Or do I need to 
> write a little function myself as no such feature exists?
> 
> Sincerely,
> Simon
> 
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