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# A. Bison Symbols

`error`
  A token name reserved for error recovery. This token may be used in grammar rules so as to allow the Bison parser to recognize an error in the grammar without halting the process. In effect, a sentence containing an error may be recognized as valid. On a parse error, the token `error` becomes the current look-ahead token. Actions corresponding to `error` are then executed, and the look-ahead token is reset to the token that originally caused the violation. See section 6. Error Recovery.

`YYABORT`
  Macro to pretend that an unrecoverable syntax error has occurred, by making `yyparse` return 1 immediately. The error reporting function `yyerror` is not called. See section The Parser Function `yyparse`.

`YYACCEPT`
  Macro to pretend that a complete utterance of the language has been read, by making `yyparse` return 0 immediately. See section The Parser Function `yyparse`.

`YYBACKUP`
  Macro to discard a value from the parser stack and fake a look-ahead token. See section Special Features for Use in Actions.

`YYERROR`
  Macro to pretend that a syntax error has just been detected: call `yyerror` and then perform normal error recovery if possible (see section 6. Error Recovery), or (if recovery is impossible) make `yyparse` return 1. See section 6. Error Recovery.

`YYERROR_VERBOSE`
  Macro that you define with `#define` in the Bison declarations section to request verbose, specific error message strings when `yyerror` is called.

`YYINITDEPTH`
  Macro for specifying the initial size of the parser stack. See section 5.8 Stack Overflow, and How to Avoid It.

`YYLEX_PARAM`
  Macro for specifying an extra argument (or list of extra arguments) for `yyparse` to pass to `yylex`. See section Calling Conventions for Pure Parsers.

`YYLTYPE`
  Macro for the data type of `yylloc`; a structure with four members. See section Textual Positions of Tokens.

`yyltype`
  Default value for YYLTYPE.

`YYMAXDEPTH`
  Macro for specifying the maximum size of the parser stack. See section 5.8 Stack Overflow, and How to Avoid It.

`YYPARSE_PARAM`
  Macro for specifying the name of a parameter that `yyparse` should accept. See section Calling Conventions for Pure Parsers.

`YYRECOVERING`
  Macro whose value indicates whether the parser is recovering from a syntax error. See section Special Features for Use in Actions.

`YYSTYPE`
  Macro for the data type of semantic values; `int` by default. See section Data Types of Semantic Values.

`yychar`
  External integer variable that contains the integer value of the current look-ahead token. (In a pure parser, it is a local variable within `yyparse`.) Error-recovery rule actions may examine this variable. See section Special Features for Use in Actions.

`yyclearin`
  Macro used in error-recovery rule actions. It clears the previous look-ahead token. See section 6. Error Recovery.

`yydebug`
  External integer variable set to zero by default. If `yydebug` is given a nonzero value, the parser will output information on input symbols and parser action. See section Debugging Your Parser.

`yyerrok`
  Macro to cause parser to recover immediately to its normal mode after a parse error. See section 6. Error Recovery.

`yyerror`
  User-supplied function to be called by `yyparse` on error. The function receives one argument, a pointer to a character string containing an error message. See section The Error Reporting Function `yyerror`.

`yylex`
  User-supplied lexical analyzer function, called with no arguments to get the next token. See section The Lexical Analyzer Function `yylex`.

`yylval`
  External variable in which `yylex` should place the semantic value associated with a token. (In a pure parser, it is a local variable within `yyparse`, and its address is passed to `yylex`.) See section Semantic Values of Tokens.

`yylloc`
  External variable in which `yylex` should place the line and column numbers associated with a token. (In a pure parser, it is a local variable within `yyparse`, and its address is passed to `yylex`.) You can ignore this variable if you don't use the ``@`' feature in the grammar actions. See section Textual Positions of Tokens.

`yynerrs`
  Global variable which Bison increments each time there is a parse error. (In a pure parser, it is a local variable within `yyparse`.) See section The Error Reporting Function `yyerror`.

`yyparse`
  The parser function produced by Bison; call this function to start parsing. See section The Parser Function `yyparse`.

`%left`
  Bison declaration to assign left associativity to token(s). See section Operator Precedence.

`%no_lines`
  Bison declaration to avoid generating `#line` directives in the parser file. See section 3.6.8 Bison Declaration Summary.

`%nonassoc`
  Bison declaration to assign nonassociativity to token(s). See section Operator Precedence.

`%prec`
  Bison declaration to assign a precedence to a specific rule. See section Context-Dependent Precedence.

`%pure_parser`
  Bison declaration to request a pure (reentrant) parser. See section A Pure (Reentrant) Parser.

`%raw`
  Bison declaration to use Bison internal token code numbers in token tables instead of the usual Yacc-compatible token code numbers. See section 3.6.8 Bison Declaration Summary.

`%right`
  Bison declaration to assign right associativity to token(s). See section Operator Precedence.

`%start`
  Bison declaration to specify the start symbol. See section The Start-Symbol.

`%token`
  Bison declaration to declare token(s) without specifying precedence. See section Token Type Names.

`%token_table`
  Bison declaration to include a token name table in the parser file. See section 3.6.8 Bison Declaration Summary.

`%type`
  Bison declaration to declare nonterminals. See section Nonterminal Symbols.

`%union`
  Bison declaration to specify several possible data types for semantic values. See section The Collection of Value Types.

These are the punctuation and delimiters used in Bison input:

``%%`'
  Delimiter used to separate the grammar rule section from the Bison declarations section or the additional C code section. See section The Overall Layout of a Bison Grammar.

``%{ %}`'
  All code listed between ``%{`' and ``%}`' is copied directly to the output file uninterpreted. Such code forms the "C declarations" section of the input file. See section Outline of a Bison Grammar.

``/*...*/`'
  Comment delimiters, as in C.

``:`'
  Separates a rule's result from its components. See section Syntax of Grammar Rules.

``;`'
  Terminates a rule. See section Syntax of Grammar Rules.

``|`'
  Separates alternate rules for the same result nonterminal. See section Syntax of Grammar Rules.

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This document was generated by Frank B. Brokken on January, 28 2005 using texi2html