Module: Gecode::Operand

Included in:
Bool::BoolOperand, BoolEnum::BoolEnumOperand, FixnumEnum::FixnumEnumOperand, Int::IntOperand, IntEnum::IntEnumOperand, SelectedSet::SelectedSetOperand, Set::SetOperand, SetElements::SetElementsOperand, SetEnum::SetEnumOperand
Defined in:
lib/gecoder/interface/constraints.rb

Overview

Describes an operand, something that a constraint can be placed on. Constraints are placed by calling #must or #must_not (the latter negates the constraint). This produces a ConstraintReceiver, which defines methods that places constraints on the operand.

In general this produces something like the following.

operand.must.constraint_method(params)

See e.g. Gecode::Int::IntOperand for concrete examples.

Classes that mix in Operand must define the methods #model and #construct_receiver. They should also define a method that converts the operand into a variable of the operand’s type (e.g. int var operands should define a method #to_int_var that returns an instance of Gecode::IntVar that represents the operand). The latter method should be used by constraints to fetch variables needed when posting constraints. The presence of the method should also be used for type checking (rather than e.g. checking whether a parameter is of type IntOperand).

Instance Method Summary collapse

Instance Method Details

#model ⇒ Object

Fetches the model that the operand belongs to.

Raises:

  • (NotImplementedError) 


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# File 'lib/gecoder/interface/constraints.rb', line 43

def model
  raise NotImplementedError, 'Abstract method has not been implemented.'
end

#must ⇒ Object Also known as: must_be

Specifies that a constraint must hold for the left hand side.



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# File 'lib/gecoder/interface/constraints.rb', line 30

def must
  construct_receiver :lhs => self, :negate => false
end

#must_not ⇒ Object Also known as: must_not_be

Specifies that the negation of a constraint must hold for the left hand side.



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# File 'lib/gecoder/interface/constraints.rb', line 37

def must_not
  construct_receiver :lhs => self, :negate => true
end