# File lib/main/parameter.rb, line 213
    def apply_casting 
      if cast?
        op = cast.respond_to?('call') ? cast : Cast[cast]
        case op.arity
          when -1
            replacement = Parameter.wrap_errors{ op.call(*values) }
            values.replace(replacement)
          else
            values.map! do |val|
              Parameter.wrap_errors{ op.call val }
            end
        end
      end
    end