Pre action that succeeds unconditionally. Used to place a C++ breakpoint at a particular rule.
<fromRuleEltNumber,toRuleEltNumber>debug;
fromRuleEltNumber - type: int
toRuleEltNumber - type: int
debug can appear in the PRE, CHECK and POST regions.
@PRE
<1,1> debug();
@RULES
_xNIL <- _xALPHA @@
Special Functions, PRE Actions