example dsl to support prolog in ruby using instance eval

prolog_in_ruby_dsl.rb

extend Prolog
  
facts do
  # possibly symbols/strings are interchangeable for atoms
  # since symbols are convenient
  editor(:alice, :vim)
  editor(:bob, :emacs)
  editor(:carol, :vim)
  editor(:devon, :emacs)

  keyboard(:alice, :qwerty)
  keyboard(:bob, :qwerty)
  keyboard(:carol, :dvorak)
  keyboard(:devon, :qwerty)
end

# Rules method makes all method calls handled by a method_missing handler on a RulesDefinition instance
rules do
  can_pair(:@person_1, :@person_2) do
    editor(:@person_1, :@x) &
    editor(:@person_2, :@x) &
    keyboard(:@person_1, :@y) &
    keyboard(:@person_2, :@y)
  end
end

query do
  can_pair(:@x, :@y) do
    # this block would be instance eval'd on a Prolog::Result
    puts "#@x can pair with #@y"
  end
end