Cross product of an array against itself n times

cross.rb

def cross values, n = 3
  Array.new(n, values).inject do |acc, i|
    acc.product(i).map(&:flatten)
  end
end

require 'set'

describe do
  it "should cross itself" do
    arr = [0, 128]
    out = [
      [0, 0, 0],
      [0, 0, 128],
      [0, 128, 0],
      [0, 128, 128],
      [128, 0, 0],
      [128, 0, 128],
      [128, 128, 0],
      [128, 128, 128],
    ]

    cross(arr).to_set.should eq out.to_set
  end
end

sqlite3 colors.db <<_EOS_
.mode column
CREATE TABLE colors (int color_value);
INSERT INTO colors VALUES (0), (128);
SELECT * FROM colors red, colors green, colors blue;
_EOS_
rm colors.db

$ sh lol.sql
0           0           0         
0           0           128       
0           128         0         
0           128         128       
128         0           0         
128         0           128       
128         128         0         
128         128         128