# PRE Region

The PRE Region is used to extend the pattern matcher's mechanism for matching each rule element. Currently, the PRE Region does not support general NLP++ expressions and statements.

## PRE Action Syntax

The actions used in the PRE Region have a mandatory range. Their form is

<num,num> pre_action_name(args....)

The PRE Action applies to each rule element in the <num, num> range individually.

PRE Actions operate only on tokens, or leaf nodes of the parse tree, at present. So, if the current node covers more than a single leaf node, the PRE Action automatically fails. Another thing to be careful of is that PRE Actions disregard the base attribute of a node. That is, even if the current node or a subnode has the base attribute set, the PRE Action will look under it for the leaf node.

## See Also

Grammar Region

PRE Action

CHECK Region

POST Region

RULES Region