Class: Rigor::Trinary

Inherits:
Object
  • Object
show all
Defined in:
lib/rigor/trinary.rb

Overview

Three-valued logic value object shared by capability queries, relational queries, and any analyzer surface that distinguishes “proven yes”, “proven no”, and “cannot prove either”.

See docs/type-specification/relations-and-certainty.md for semantics and docs/internal-spec/internal-type-api.md for the contract.

Constant Summary collapse

VALUES = 
%i[yes no maybe].freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(value) ⇒ Trinary

Returns a new instance of Trinary.

Raises:

  • (ArgumentError) 


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# File 'lib/rigor/trinary.rb', line 39

def initialize(value)
  raise ArgumentError, "unknown trinary value: #{value.inspect}" unless VALUES.include?(value)

  @value = value
end

Instance Attribute Details

#value ⇒ Object (readonly)

Returns the value of attribute value.



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# File 'lib/rigor/trinary.rb', line 37

def value
  @value
end

Class Method Details

.from_symbol(symbol) ⇒ Object 



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# File 'lib/rigor/trinary.rb', line 26

def from_symbol(symbol)
  case symbol
  when :yes then yes
  when :no then no
  when :maybe then maybe
  else
    raise ArgumentError, "unknown trinary value: #{symbol.inspect}"
  end
end

.maybe ⇒ Object 



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# File 'lib/rigor/trinary.rb', line 22

def maybe
  @maybe ||= new(:maybe).freeze
end

.no ⇒ Object 



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# File 'lib/rigor/trinary.rb', line 18

def no
  @no ||= new(:no).freeze
end

.yes ⇒ Object 



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# File 'lib/rigor/trinary.rb', line 14

def yes
  @yes ||= new(:yes).freeze
end

Instance Method Details

#==(other) ⇒ Object Also known as: eql? 



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# File 'lib/rigor/trinary.rb', line 83

def ==(other)
  other.is_a?(Trinary) && value == other.value
end

#and(other) ⇒ Object

Conjunction. yes & yes = yes, no with anything = no, otherwise maybe.



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# File 'lib/rigor/trinary.rb', line 66

def and(other)
  coerced = coerce(other)
  return self.class.no if no? || coerced.no?
  return self.class.yes if yes? && coerced.yes?

  self.class.maybe
end

#hash ⇒ Object 



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# File 'lib/rigor/trinary.rb', line 88

def hash
  value.hash
end

#inspect ⇒ Object 



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# File 'lib/rigor/trinary.rb', line 96

def inspect
  "#<Rigor::Trinary #{value}>"
end

#maybe? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rigor/trinary.rb', line 53

def maybe?
  value == :maybe
end

#negate ⇒ Object 



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# File 'lib/rigor/trinary.rb', line 57

def negate
  case value
  when :yes then self.class.no
  when :no then self.class.yes
  when :maybe then self.class.maybe
  end
end

#no? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rigor/trinary.rb', line 49

def no?
  value == :no
end

#or(other) ⇒ Object

Disjunction. yes with anything = yes, no & no = no, otherwise maybe.



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# File 'lib/rigor/trinary.rb', line 75

def or(other)
  coerced = coerce(other)
  return self.class.yes if yes? || coerced.yes?
  return self.class.no if no? && coerced.no?

  self.class.maybe
end

#to_s ⇒ Object 



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# File 'lib/rigor/trinary.rb', line 92

def to_s
  value.to_s
end

#yes? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rigor/trinary.rb', line 45

def yes?
  value == :yes
end