# File ai/csp/constraint.rb, line 130
        def propagate(variable, level)
            uninstantiated_variables.each {|v|
                v.each_value_with_index(level) { |value, index|
                    v.prune(level, index) unless value == variable.value
                }
                return false if v.domain_empty?
            }
            true
        end