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 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.  *Note The Parser Function
     `yyparse': Parser Function.

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

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

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

`YYLEX_PARAM'
     Macro for specifying an extra argument (or list of extra
     arguments) for `yyparse' to pass to `yylex'.  *Note Calling
     Conventions for Pure Parsers: Pure Calling.

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

`yyltype'
     Default value for YYLTYPE.

`YYMAXDEPTH'
     Macro for specifying the maximum size of the parser stack.  
See Stack Overflow.

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

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

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

`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 Special Features for Use in Actions: Action Features.

`yyclearin'
     Macro used in error-recovery rule actions.  It clears the previous
     look-ahead token.  See 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 Debugging Your Parser: Debugging.

`yyerrok'
     Macro to cause parser to recover immediately to its normal mode
     after a parse error.  See 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.  *Note The Error Reporting Function
     `yyerror': Error Reporting.

`yylex'
     User-supplied lexical analyzer function, called with no arguments
     to get the next token.  *Note The Lexical Analyzer Function
     `yylex': Lexical.

`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 Semantic Values of Tokens: Token Values.

`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.  *Note Textual Positions of
     Tokens: Token Positions.

`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 The Error Reporting Function `yyerror': Error Reporting.

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

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

`%no_lines'
     Bison declaration to avoid generating `#line' directives in the
     parser file.  See Decl Summary.

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

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

`%pure_parser'
     Bison declaration to request a pure (reentrant) parser.  *Note A
     Pure (Reentrant) Parser: Pure Decl.

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

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

`%start'
     Bison declaration to specify the start symbol.  *Note The
     Start-Symbol: Start Decl.

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

`%token_table'
     Bison declaration to include a token name table in the parser file.
     See Decl Summary.

`%type'
     Bison declaration to declare nonterminals.  *Note Nonterminal
     Symbols: Type Decl.

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

   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.  *Note The
     Overall Layout of a Bison Grammar: Grammar Layout.

`%{ %}'
     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 Outline of a Bison Grammar: Grammar Outline.

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

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

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

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