This is an enumeration variable designed to keep track of the status of a given node. HL_NodeMark can be any of the following possible values:
NMARK_ORIGINAL=0 NMARK_CHANGED=1 NMARK_SELECT=2A node with HL_NodeMark=NMARK_CHANGED can be used to mark that it has been modified. A node with HL_NodeMark=NMARK_SELECT can be used to mark a node for modification.