10.2.6 Special Features for Use in Java Actions

The following special constructs can be uses in Java actions. Other analogous C action features are currently unavailable for Java.

Use %define throws to specify any uncaught exceptions from parser actions, and initial actions specified by %initial-action.

Variable: $n

The semantic value for the nth component of the current rule. This may not be assigned to. See section Java Semantic Values.

Variable: $<typealt>n

Like $n but specifies a alternative type typealt. See section Java Semantic Values.

Variable: $$

The semantic value for the grouping made by the current rule. As a value, this is in the base type (Object or as specified by %define stype) as in not cast to the declared subtype because casts are not allowed on the left-hand side of Java assignments. Use an explicit Java cast if the correct subtype is needed. See section Java Semantic Values.

Variable: $<typealt>$

Same as $$ since Java always allow assigning to the base type. Perhaps we should use this and $<>$ for the value and $$ for setting the value but there is currently no easy way to distinguish these constructs. See section Java Semantic Values.

Variable: @n

The location information of the nth component of the current rule. This may not be assigned to. See section Java Location Values.

Variable: @$

The location information of the grouping made by the current rule. See section Java Location Values.

Statement: return YYABORT;

Return immediately from the parser, indicating failure. See section Java Parser Interface.

Statement: return YYACCEPT;

Return immediately from the parser, indicating success. See section Java Parser Interface.

Statement: return YYERROR;

Start error recovery without printing an error message. See section Error Recovery.

Statement: return YYFAIL;

Print an error message and start error recovery. See section Error Recovery.

Function: boolean recovering ()

Return whether error recovery is being done. In this state, the parser reads token until it reaches a known state, and then restarts normal operation. See section Error Recovery.

Function: protected void yyerror (String msg)

Function: protected void yyerror (Position pos, String msg)

Function: protected void yyerror (Location loc, String msg)

Print an error message using the yyerror method of the scanner instance in use.