Class: Rubylog::Predicate

Inherits:
Object show all
Defined in:
lib/rubylog/predicate.rb

Direct Known Subclasses

Primitive, Procedure

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(functor, arity) ⇒ Predicate

Returns a new instance of Predicate.



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# File 'lib/rubylog/predicate.rb', line 5

def initialize functor, arity
  @functor = functor
  @arity = arity
end

Instance Attribute Details

#arity ⇒ Object (readonly)

Returns the value of attribute arity.



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# File 'lib/rubylog/predicate.rb', line 4

def arity
  @arity
end

#functor ⇒ Object (readonly)

Returns the value of attribute functor.



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# File 'lib/rubylog/predicate.rb', line 4

def functor
  @functor
end

Instance Method Details

#add_functor_to(subjects) ⇒ Object 



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# File 'lib/rubylog/predicate.rb', line 15

def add_functor_to subjects
  if arity == 0
    # We treat nullary predicates differently. Do not even create functors.
    Rubylog::NullaryPredicates[functor] = self
    return
  end

  predicate = self

  [subjects].flatten.each do |subject|
    raise ArgumentError, "#{subject.inspect} is not a class or module" unless subject.is_a? Module
    subject.class_eval do
      f = predicate.functor
      define_method f do |*args, &block|
      args << block if block
      Rubylog::Structure.new predicate, f, self, *args 
      end

      f_bang = :"#{f}!"
      define_method f_bang do |*args, &block|
      args << block if block
      predicate.assert Rubylog::Structure.new(predicate, f, self, *args), :true
      self
      end

      f_qmark = :"#{f}?"
      define_method f_qmark do |*args, &block|
      args << block if block
      Rubylog::Structure.new(predicate, f, self, *args).true?
      end
    end
  end

end

#call(*args) ⇒ Object

Yields for each solution of the predicate



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# File 'lib/rubylog/predicate.rb', line 11

def call *args
  raise "abstract method called on #{self.inspect}"
end