Seive of Eratosthenes

seive_of_eratosthenes.swift

import Cocoa

enum Status {
    case unmarked, prime, composite
}

class SeiveOfEratosthenes {
    let ceiling: Int
    let ceiling_sqrt: Int
    var table = [Int: Status]()
    var results = [Int]()
    
    init(ceiling: Int){
        self.ceiling = ceiling
        self.ceiling_sqrt = Int(sqrt(Double(ceiling)))
        // Initialize table as all numbers unmarked
        for index in 2...(self.ceiling) {
            self.table[index] = Status.unmarked
        }
    }
    
    
    func mark_table() {
        for index in 2...ceiling_sqrt {
            if table[index] != Status.unmarked{
                continue
            }
            self.table[index] = Status.prime
            var multiples_of_index = index
            
            while (multiples_of_index < ceiling) {
                multiples_of_index = multiples_of_index + index
                table[multiples_of_index] = Status.composite
            }
        }
        
        for (key, value) in table {
            if value != Status.composite {
            results.append(key)
            }
        }
        
    }
    
    func get_table() -> Dictionary<Int,Status> {
        return self.table
    }
    
    func get_results () -> [Int] {
        return sorted(self.results)
    }
}

var seive = SeiveOfEratosthenes(ceiling: 100)
seive.mark_table()
println(seive.get_results())