A. Bison Symbols

Variable: @$: In an action, the location of the left-hand side of the rule. See section Locations Overview.

Variable: @n: In an action, the location of the n-th symbol of the right-hand side of the rule. See section Locations Overview.

Variable: $$: In an action, the semantic value of the left-hand side of the rule. See section Actions.

Variable: $n: In an action, the semantic value of the n-th symbol of the right-hand side of the rule. See section Actions.

Delimiter: %%: Delimiter used to separate the grammar rule section from the Bison declarations section or the epilogue. See section The Overall Layout of a Bison Grammar.

Delimiter: %{code%}: All code listed between ‘%{’ and ‘%}’ is copied directly to the output file uninterpreted. Such code forms the prologue of the input file. See section Outline of a Bison Grammar.

Construct: /*…*/: Comment delimiters, as in C.

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

Delimiter: ;: Terminates a rule. See section Syntax of Grammar Rules.

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

Symbol: $accept: The predefined nonterminal whose only rule is ‘$accept: start $end’, where start is the start symbol. See section The Start-Symbol. It cannot be used in the grammar.

Directive: %debug: Equip the parser for debugging. See section Bison Declaration Summary.

Directive: %defines: Bison declaration to create a header file meant for the scanner. See section Bison Declaration Summary.

Directive: %destructor: Specify how the parser should reclaim the memory associated to discarded symbols. See section Freeing Discarded Symbols.

Directive: %dprec: Bison declaration to assign a precedence to a rule that is used at parse time to resolve reduce/reduce conflicts. See section Writing GLR Parsers.

Symbol: $end: The predefined token marking the end of the token stream. It cannot be used in the grammar.

Symbol: 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 syntax 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 Error Recovery.

Directive: %error-verbose: Bison declaration to request verbose, specific error message strings when yyerror is called.

Directive: %file-prefix="prefix": Bison declaration to set the prefix of the output files. See section Bison Declaration Summary.

Directive: %glr-parser: Bison declaration to produce a GLR parser. See section Writing GLR Parsers.

Directive: %initial-action: Run user code before parsing. See section Performing Actions before Parsing.

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

Directive: %lex-param {argument-declaration}: Bison declaration to specifying an additional parameter that yylex should accept. See section Calling Conventions for Pure Parsers.

Directive: %merge: Bison declaration to assign a merging function to a rule. If there is a reduce/reduce conflict with a rule having the same merging function, the function is applied to the two semantic values to get a single result. See section Writing GLR Parsers.

Directive: %name-prefix="prefix": Bison declaration to rename the external symbols. See section Bison Declaration Summary.

Directive: %no-lines: Bison declaration to avoid generating #line directives in the parser file. See section Bison Declaration Summary.

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

Directive: %output="file": Bison declaration to set the name of the parser file. See section Bison Declaration Summary.

Directive: %parse-param {argument-declaration}: Bison declaration to specifying an additional parameter that yyparse should accept. See section The Parser Function yyparse.

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

Directive: %pure-parser: Bison declaration to request a pure (reentrant) parser. See section A Pure (Reentrant) Parser.

Directive: %require "version": Require version version or higher of Bison. See section Require a Version of Bison.

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

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

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

Directive: %token-table: Bison declaration to include a token name table in the parser file. See section Bison Declaration Summary.

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

Symbol: $undefined: The predefined token onto which all undefined values returned by yylex are mapped. It cannot be used in the grammar, rather, use error.

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

Macro: 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.

Macro: 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.

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

Variable: yychar: External integer variable that contains the integer value of the 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.

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

Macro: YYDEBUG: Macro to define to equip the parser with tracing code. See section Tracing Your Parser.

Variable: 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 Tracing Your Parser.

Macro: yyerrok: Macro to cause parser to recover immediately to its normal mode after a syntax error. See section Error Recovery.

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

Function: yyerror: User-supplied function to be called by yyparse on error. See section The Error Reporting Function yyerror.

Macro: YYERROR_VERBOSE: An obsolete macro that you define with #define in the prologue to request verbose, specific error message strings when yyerror is called. It doesn't matter what definition you use for YYERROR_VERBOSE, just whether you define it. Using %error-verbose is preferred.

Macro: YYINITDEPTH: Macro for specifying the initial size of the parser stack. See section Memory Management, and How to Avoid Memory Exhaustion.

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

Macro: YYLEX_PARAM: An obsolete macro for specifying an extra argument (or list of extra arguments) for yyparse to pass to yylex. The use of this macro is deprecated, and is supported only for Yacc like parsers. See section Calling Conventions for Pure Parsers.

Variable: 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 Locations of Tokens. In semantic actions, it stores the location of the look-ahead token. See section Actions and Locations.

Type: YYLTYPE: Data type of yylloc; by default, a structure with four members. See section Data Types of Locations.

Variable: 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. In semantic actions, it stores the semantic value of the look-ahead token. See section Actions.

Macro: YYMAXDEPTH: Macro for specifying the maximum size of the parser stack. See section Memory Management, and How to Avoid Memory Exhaustion.

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

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

Macro: YYPARSE_PARAM: An obsolete macro for specifying the name of a parameter that yyparse should accept. The use of this macro is deprecated, and is supported only for Yacc like parsers. See section Calling Conventions for Pure Parsers.

Macro: YYRECOVERING: The expression YYRECOVERING () yields 1 when the parser is recovering from a syntax error, and 0 otherwise. See section Special Features for Use in Actions.

Macro: YYSTACK_USE_ALLOCA

Macro used to control the use of alloca when the C LALR(1) parser needs to extend its stacks. If defined to 0, the parser will use malloc to extend its stacks. If defined to 1, the parser will use alloca. Values other than 0 and 1 are reserved for future Bison extensions. If not defined, YYSTACK_USE_ALLOCA defaults to 0.

In the all-too-common case where your code may run on a host with a limited stack and with unreliable stack-overflow checking, you should set YYMAXDEPTH to a value that cannot possibly result in unchecked stack overflow on any of your target hosts when alloca is called. You can inspect the code that Bison generates in order to determine the proper numeric values. This will require some expertise in low-level implementation details.

Type: YYSTYPE: Data type of semantic values; int by default. See section Data Types of Semantic Values.

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