26 2012-02-22 21:22:00 +0100 'Type error' reporting in length/2 2012-02-22 21:22:21 +0100 1 1 1 Unclassified SWI-Prolog core 5.11.x PC Windows CONFIRMED Highest minor --- 1 paul bugs 80 paul 2012-02-22 21:22:21 +0100 In or out of ISO mode, 1 ?- length(a, _). ERROR: length/2: Type error: `list' expected, found `a' looks right to me, but 2 ?- length(a, 0). false. should presumably throw the Type error too. cheers - Paul