groovy-eratosthenes-sieve

Implementation of eratosthenes sieve in Groovy.

Reference: https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes
Reference: http://docs.groovy-lang.org/latest/html/documentation/#_range_operator

preface

In mathematics, the sieve of Eratosthenes is a simple, ancient algorithm for finding all prime numbers up to any given limit.

For more info take a look at reference.

project description

Used groovy features (examples in OperationsTest):

• range operator ..

  expect:
  5..Math.sqrt(40) == [5, 6]    
  

• overloaded - on lists

  expect:
  [1] - 1 == []    
  

• step

  expect:
  (1..10).step(5) == [1, 6]    
  

and the algorithm is a simple combination of features mentioned above:

static def get(limit) {
    def sieve = 2..limit
    (2..Math.sqrt(limit)).each { k -> sieve -= ((2*k)..(sieve.last()+1)).step(k) }
    return sieve
}