A prime number can only be divisible by 1 and itself with the result being a whole number. Even numbers cannot be prime as they are always divisible by 2.
1. list all numbers between 2 and 700
2. remove all even numbers
3. next remove multiples of all prime numbers up to the square root of the highest number that you are checking for primes (700)
put empty into field "Field 1"
put empty into field "Field 2"
-- list numbers
repeat with i = 2 to 700
put i & return after field "Field 1"
put the number of lines of field "Field 1" into tLines
-- remove even numbers
repeat with j = 3 to tLines
if j mod 2 <> 0 then
put j & return after field "Field 2"
-- calculate square root of highest number (700)
put the sqrt of 700 into tSqrt
-- remove all multiples upto the square root
-- stuck !!!
Builds two arrays, indexed by “known to be prime and in the range of interest”, and “known to be not prime”.
put fld "FieldIn" into tInput
if the number of words in tInput <> 2 or \
word 1 of tInput is not a number or \
word 2 of tInput is not a number then
ask "must give 2 numbers"
local tAPrime, tANonPrime
repeat with i = 2 to word 2 of tInput
if tANonPrime[i] then next repeat
if i >= word 1 of tInput then put true into tAPrime[i]
repeat with j = i+i to word 2 of tInput step i
put true into tANonPrime[j]
put "The number of primes between" && tInput && "is" && the number of lines in the keys of tAPrime & CR into fld "F"
put the keys of tAPrime into tt
sort lines of tt numeric
put "and they are" & CR & tt after fld "F"
— make an array with uneven numbers between 21 up to 699
put “” into tCollect
repeat with i = 21 to 700 -2 step 2
put true into tCollect[i]
— get max number that multiplied by 3 will be below 700
— because all I can do is multiply
put trunc (700/3) into tMax
put 3 into tStartVal
repeat with i = 3 to tMax step 2
repeat with j = tStartVal to tMax step 2
put i * j into tSum
if tSum < 700 then
put false into tCollect[tSum]
— we are above 700 –> next round
add 2 to tStartVal — took this idea from Alex Tweedly’s code
put the keys of tCollect into tKeys
repeat for each line aKey in tKeys
if tCollect[aKey] = true then put aKey & return after tCollect2
delete last char of tCollect2 — a return
sort tCollect2 ascending numeric
put “there are ” & the number of lines of tCollect2 && “prime numbers” & cr & tCollect2 into field 1