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
    repeat with i from 5 to (n ^ 0.5) div 1 by 6
        if ((n mod i is 0) or (n mod (i + 2) is 0)) then return false
    end repeat

    return true
end isPrime

-- Test code:
set output to {}
repeat with n from -7 to 100
    if (isPrime(n)) then set end of output to n
end repeat
return output