#!/usr/bin/ruby

module ConstraintSolver
    # This class represents a list of constraints.
    class ConstraintList < Array
	# Returns the ConstraintList that contains all constraints that involve
	# variable and have values assigned to not all variables involved.
	def notAllAssignedWithVariable(variable)
	    ConstraintList.new(self.select { |constraint|
		constraint.include?(variable) and not constraint.allAssigned?
	    })
	end
	#
	# Returns the ConstraintList that contains all constraints that involve
	# variable.
	def allWithVariable(variable)
	    ConstraintList.new(self.select { |constraint|
		constraint.include?(variable)
	    })
	end

	def sort(&block)
	    ConstraintList.new(self.sort!(&block))
	end

	def -(element)
	    new = self.to_a - (element.kind_of?(Array) ? element : [ element ])
	    return ConstraintList.new(new)
	end
    end
end