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120 Bison 2.3<br />

%type<br />

[Directive]<br />

Bison declaration to declare nonterminals. See Section 3.7.5 [Nonterminal Symbols],<br />

page 56.<br />

$undefined<br />

[Symbol]<br />

The predefined token onto which all undefined values returned by yylex are mapped.<br />

It cannot be used in the grammar, rather, use error.<br />

%union<br />

[Directive]<br />

Bison declaration to specify several possible data types for semantic values. See<br />

Section 3.7.4 [The Collection of Value Types], page 55.<br />

YYABORT<br />

[Macro]<br />

Macro to pretend that an unrecoverable syntax error has occurred, by making yyparse<br />

return 1 immediately. The error reporting function yyerror is not called. See Section<br />

4.1 [The Parser Function yyparse], page 63.<br />

YYACCEPT<br />

[Macro]<br />

Macro to pretend that a complete utterance of the language has been read, by making<br />

yyparse return 0 immediately. See Section 4.1 [The Parser Function yyparse],<br />

page 63.<br />

YYBACKUP<br />

[Macro]<br />

Macro to discard a value from the parser stack and fake a look-ahead token. See<br />

Section 4.4 [Special Features for Use in Actions], page 68.<br />

yychar<br />

[Variable]<br />

External integer variable that contains the integer value of the look-ahead token. (In<br />

a pure parser, it is a local variable within yyparse.) Error-recovery rule actions may<br />

examine this variable. See Section 4.4 [Special Features for Use in Actions], page 68.<br />

yyclearin<br />

[Variable]<br />

Macro used in error-recovery rule actions. It clears the previous look-ahead token.<br />

See Chapter 6 [Error Recovery], page 83.<br />

YYDEBUG<br />

[Macro]<br />

Macro to define to equip the parser with tracing code. See Section 8.2 [Tracing Your<br />

Parser], page 95.<br />

yydebug<br />

[Variable]<br />

External integer variable set to zero by default. If yydebug is given a nonzero value,<br />

the parser will output information on input symbols and parser action. See Section 8.2<br />

[Tracing Your Parser], page 95.<br />

yyerrok<br />

[Macro]<br />

Macro to cause parser to recover immediately to its normal mode after a syntax error.<br />

See Chapter 6 [Error Recovery], page 83.<br />

YYERROR<br />

[Macro]<br />

Macro to pretend that a syntax error has just been detected: call yyerror and then<br />

perform normal error recovery if possible (see Chapter 6 [Error Recovery], page 83),

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