Mersenne primes: Difference between revisions

<syntaxhighlight lang="applescript">

----

Or more efficiently:

<syntaxhighlight lang="applescript">on isPrime(n)

if (n < 4) then return (n > 1)

if ((n mod 2 is 0) or (n mod 3 is 0)) then return false

set {i, max} to {5, (n ^ 0.5) div 1}

repeat until (i > max)

if ((n mod i is 0) or (n mod (i + 2) is 0)) then return false

set i to i + 6

end repeat

return true

end isPrime

on join(lst, delim)

set astid to AppleScript's text item delimiters

set AppleScript's text item delimiters to delim

set txt to lst as text

set AppleScript's text item delimiters to astid

return txt

end join

on mersennePrimes()

set output to {"Mersenne primes within AppleScript's number precision:"}

-- Special-case 2 ^ 2 - 1.

set end of output to "2 ^ 2 - 1 = 3"

set p to 1 -- Otherwise test odd-numbered powers of 2.

try -- Survive the "numeric operation too large" error when it occurs.

repeat

set p to p + 2

if ((isPrime(p)) and (isPrime(2 ^ p - 1))) then ¬

set end of output to "2 ^ " & p & " - 1 = " & (2 ^ p div 1 - 1)

end repeat

end try

return join(output, linefeed)

end mersennePrimes

mersennePrimes()</syntaxhighlight>

{{output}}

<syntaxhighlight lang="applescript">"Mersenne primes within AppleScript's number precision:

2 ^ 2 - 1 = 3

2 ^ 3 - 1 = 7

2 ^ 5 - 1 = 31

2 ^ 7 - 1 = 127

2 ^ 13 - 1 = 8191

2 ^ 17 - 1 = 131071

2 ^ 19 - 1 = 524287

2 ^ 31 - 1 = 2.147483647E+9"</syntaxhighlight>