declare Enumerate GenerateOdd ListDivisorsOf ListPrimesUntil EnumerateLazy Primes in

fun {Enumerate Start End} Inner in
    fun {Inner Start End}
        if End == Start then
            Start|nil
        else
            Start|{Inner (Start+1) End}
        end
    end 
    thread {Inner Start End} end
end

fun {GenerateOdd Start End}
    thread {Filter {Enumerate Start End} fun {$ N} N mod 2 \= 0 end} end
end

fun {ListDivisorsOf Number}
    thread {Filter {Enumerate 1 Number} fun {$ N} Number mod N == 0 end} end
end

fun {ListPrimesUntil Number}
    thread {Filter {Enumerate 2 Number} fun {$ N} {List.length {ListDivisorsOf N}} == 2 end} end
end

fun lazy {EnumerateLazy}
    % stolen from
    % https://github.com/alhassy/OzCheatSheet?tab=readme-ov-file#lazy-evaluation
    fun lazy {Ints N} N|{Ints N+1} end
    in {Ints 1}
end

fun lazy {Primes}
    {Filter {EnumerateLazy} fun {$ N} {List.length {ListDivisorsOf N}} == 2 end}
end