Example: Sieve of Eratosthenes

Description

Deliver prime numbers up to a specified integer limit. Compute prime numbers using sieve of Eratosthenes.

Notes

This example uses the iteration (across) form of the Eiffel loop construct to traverse a list, an array, and an integer interval.

Source

Problem description from Rosetta Code

Solution

class APPLICATION create make feature make -- Run application. do across primes_through (100) as ic loop print (ic.item.out + " ") end end primes_through (a_limit: INTEGER): LINKED_LIST [INTEGER] -- Prime numbers through `a_limit' require valid_upper_limit: a_limit >= 2 local l_tab: ARRAY [BOOLEAN] do create Result.make create l_tab.make_filled (True, 2, a_limit) across l_tab as ic loop if ic.item then Result.extend (ic.target_index) across ((ic.target_index * ic.target_index) |..| l_tab.upper).new_cursor.with_step (ic.target_index) as id loop l_tab [id.item] := False end end end end end

Output

2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97