Defines the interface for a rule used in the scanning of text for the purpose of
document partitioning or text styling. A predicate rule can only return one single
token after having successfully detected content. This token is called success token.
Also, it also returns a token indicating that this rule has not been successful.
Evaluates the rule by examining the characters available from
the provided character scanner. The token returned by this rule
returns true when calling isUndefined,
if the text that the rule investigated does not match the rule's requirements. Otherwise,
this method returns this rule's success token. If this rules relies on a text pattern
comprising a opening and a closing character sequence this method can also be called
when the scanner is positioned already between the opening and the closing sequence.
In this case, resume must be set to true.
scanner - the character scanner to be used by this rule
resume - indicates that the rule starts working between the opening and the closing character sequence