Ruby Implementation of Merge Sort

merge_sort.rb

def merge_sort(array)
  # set base case to allows the recursion to work and not go on indefinitely.
  return array if array.size <= 1
  
  # split the array into two 
  left, right = array.each_slice((array.size/2).round).to_a

  # merge the mergesorted left half with the mergesorted right half.
  merge = -> (left, right) {
    array = []
    while left.size > 0 && right.size > 0
      array << (left[0] < right[0] ? left.shift : right.shift)
    end

    return array + left + right
  }
  
  return merge.call merge_sort(left), merge_sort(right)
end