Class: Predicate

Inherits:
Formula show all
Defined in:
lib/rover_prover/language/formula/predicate.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name, terms) ⇒ Predicate

Returns a new instance of Predicate.



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# File 'lib/rover_prover/language/formula/predicate.rb', line 6

def initialize(name, terms)
  @name = name
  @terms = terms
end

Instance Attribute Details

#name ⇒ Object (readonly)

Returns the value of attribute name.



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# File 'lib/rover_prover/language/formula/predicate.rb', line 4

def name
  @name
end

#terms ⇒ Object (readonly)

Returns the value of attribute terms.



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# File 'lib/rover_prover/language/formula/predicate.rb', line 4

def terms
  @terms
end

Instance Method Details

#eql?(exp) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rover_prover/language/formula/predicate.rb', line 37

def eql?(exp)
  return false unless exp.is_a?(Predicate)
  return false unless @name == exp.name
  return false unless @terms.length == exp.terms.length
  @terms.zip(exp.terms).all? { |t1, t2| t1.eql?(t2) }
end

#free_unification_terms ⇒ Object 



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# File 'lib/rover_prover/language/formula/predicate.rb', line 15

def free_unification_terms
  @terms.map(&:free_unification_terms).flatten.uniq
end

#free_variables ⇒ Object 



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# File 'lib/rover_prover/language/formula/predicate.rb', line 11

def free_variables
  @terms.map(&:free_variables).flatten.uniq
end

#occurs(unification_term) ⇒ Object 



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# File 'lib/rover_prover/language/formula/predicate.rb', line 28

def occurs(unification_term)
  @terms.any? { |term| term.occurs(unification_term) }
end

#replace(old, new) ⇒ Object 



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# File 'lib/rover_prover/language/formula/predicate.rb', line 19

def replace(old, new)
  return new if eql?(old)
  Predicate.new(@name, @terms.map { |term| term.replace(old, new) })
end

#set_instantiation_time(time) ⇒ Object 



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# File 'lib/rover_prover/language/formula/predicate.rb', line 24

def set_instantiation_time(time)
  @terms.each{ |term| term.set_instantiation_time(time) }
end

#to_s ⇒ Object 



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# File 'lib/rover_prover/language/formula/predicate.rb', line 32

def to_s
  terms_s = @terms.empty? ? "" : "(#{@terms.map(&:to_s).join(', ')})"
  "#{@name}#{terms_s}"
end

#unify(term) ⇒ Object 



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# File 'lib/rover_prover/language/formula/predicate.rb', line 44

def unify(term)
  return term.unify(self) if term.is_a?(UnificationTerm)
  return nil unless term.is_a?(Predicate)
  return nil unless @name == term.name
  return nil unless @terms.length == term.terms.length
  term_pair = @terms.zip(term.terms)
  subst = {}

  term_pair.each do |term_a, term_b|
    subst.each do |k, v| 
      term_a = term_a.replace(k, v)
      term_b = term_b.replace(k, v)
    end
    sub = term_a.unify(term_b)
    return nil if sub == nil
    subst.merge!(sub)
  end
  subst
end