Veritas.rb

$LOAD_PATH.unshift '/home/alexis/veritas/lib'

require 'veritas'
include Veritas

header = Relation::Header.new([[:name, String], [:is_admin, Integer], [:is_author, Integer]])
body = [['Foo', 1, 1], ['Bar', 1, 0], ['Baz', 0, 1]].each

users = Relation.new(header, body)
admins = Relation.new(header, body).restrict { |r| r[:is_admin].eq(1) }
authors = Relation.new(header, body).restrict { |r| r[:is_author].eq(1) }

users & authors - admins