Contents

#!/usr/bin/ruby

module ConstraintSolver
    # Represents a constraint. To be used as a guidance to see which methods
    # constraints need to implement.
    class AbstractConstraint
	# Checks whether the constraint holds for the current assignments of the
	# involved variables.
	def holds?
	    raise RuntimeError, "must implement holds?"
	end

	# Checks whether all variables involved in the constraint have values
	# assigned to them.
	def allAssigned?
	    raise RuntimeError, "must implement allAssigned?"
	end

	# Checks whether the constraint includes variable.
	def include?(variable)
	    raise RuntimeError, "must implement include?(variable)"
	end

	# Iterates over all the variables involved in the constraint.
	def each
	    raise RuntimeError, "must implement each"
	end

	# Prunes the values from the domains of the involved variables that
	# cannot be assigned to the respective variables because the constraint
	# would be violated. Returns a list of the variables whose domains were
	# pruned, the number of times the constraint was checked, and whether a
	# domain wipeout occured.
	def revise
	    raise RuntimeError, "must implement revise"
	end

	# Returns the cost of violating the constraint. This should be infinity
	# (or reasonably close to it) for hard constraints and a positive number
	# for soft constraints.
	def violationCost
	    raise RuntimeError, "must implement violationCost"
	end
    end
end

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
ConstraintSolver-0.1	lib/AbstractConstraint.rb