Note The statistics package records mode '--' when the corresponding argument was not instantiated, however this condition is not enough for the output mode - an output mode argument must not be a suspending variable and it must not occur in other arguments of the call. Therefore for some procedures the mode declaration printed by print_modes/0 will not be correct and the program might not run with it.
Success: [eclipse]: [nrev]. /home/eclipse/nrev.sd loaded 2928 bytes in 0.07 seconds yes. [eclipse]: set_flag(statistics, mode), debug(nreverse([1,2,3], _)). Start debugging - leap mode Stop debugging. yes. [eclipse]: print_modes. :- mode nreverse(++, -), append(++, ++, -). Fail: set_flag(statistics, all), print_modes.