Ceci est le fichier Info bison.info, produit par Makeinfo version 4.0b à partir bison.texinfo. START-INFO-DIR-ENTRY * bison: (bison). GNU Project parser generator (yacc replacement). END-INFO-DIR-ENTRY This file documents the Bison parser generator. Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1995, 1998, 1999, 2000 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the sections entitled "GNU General Public License" and "Conditions for Using Bison" are included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the sections entitled "GNU General Public License", "Conditions for Using Bison" and this permission notice may be included in translations approved by the Free Software Foundation instead of in the original English.  File: bison.info, Node: Table of Symbols, Next: Glossary, Prev: Invocation, Up: Top 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. *Note 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. *Note 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 (*note Error Recovery::), or (if recovery is impossible) make `yyparse' return 1. *Note 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. *Note 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. *Note Data Types of Locations: Location Type. `yyltype' Default value for YYLTYPE. `YYMAXDEPTH' Macro for specifying the maximum size of the parser stack. *Note Stack Overflow::. `YYPARSE_PARAM' Macro for specifying the name of a parameter that `yyparse' should accept. *Note Calling Conventions for Pure Parsers: Pure Calling. `YYRECOVERING' Macro whose value indicates whether the parser is recovering from a syntax error. *Note Special Features for Use in Actions: Action Features. `YYSTYPE' Macro for the data type of semantic values; `int' by default. *Note 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. *Note Special Features for Use in Actions: Action Features. `yyclearin' Macro used in error-recovery rule actions. It clears the previous look-ahead token. *Note 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. *Note Debugging Your Parser: Debugging. `yyerrok' Macro to cause parser to recover immediately to its normal mode after a parse error. *Note 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'.) *Note 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'.) *Note The Error Reporting Function `yyerror': Error Reporting. `yyparse' The parser function produced by Bison; call this function to start parsing. *Note The Parser Function `yyparse': Parser Function. `%debug' Equip the parser for debugging. *Note Decl Summary::. `%defines' Bison declaration to create a header file meant for the scanner. *Note Decl Summary::. `%left' Bison declaration to assign left associativity to token(s). *Note Operator Precedence: Precedence Decl. `%no_lines' Bison declaration to avoid generating `#line' directives in the parser file. *Note Decl Summary::. `%nonassoc' Bison declaration to assign non-associativity to token(s). *Note Operator Precedence: Precedence Decl. `%prec' Bison declaration to assign a precedence to a specific rule. *Note Context-Dependent Precedence: Contextual Precedence. `%pure_parser' Bison declaration to request a pure (reentrant) parser. *Note A Pure (Reentrant) Parser: Pure Decl. `%right' Bison declaration to assign right associativity to token(s). *Note 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. *Note Token Type Names: Token Decl. `%token_table' Bison declaration to include a token name table in the parser file. *Note 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. *Note 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. *Note 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. *Note Syntax of Grammar Rules: Rules. `|' Separates alternate rules for the same result nonterminal. *Note Syntax of Grammar Rules: Rules.  File: bison.info, Node: Glossary, Next: Index, Prev: Table of Symbols, Up: Top Glossary ******** Backus-Naur Form (BNF) Formal method of specifying context-free grammars. BNF was first used in the `ALGOL-60' report, 1963. *Note Languages and Context-Free Grammars: Language and Grammar. Context-free grammars Grammars specified as rules that can be applied regardless of context. Thus, if there is a rule which says that an integer can be used as an expression, integers are allowed _anywhere_ an expression is permitted. *Note Languages and Context-Free Grammars: Language and Grammar. Dynamic allocation Allocation of memory that occurs during execution, rather than at compile time or on entry to a function. Empty string Analogous to the empty set in set theory, the empty string is a character string of length zero. Finite-state stack machine A "machine" that has discrete states in which it is said to exist at each instant in time. As input to the machine is processed, the machine moves from state to state as specified by the logic of the machine. In the case of the parser, the input is the language being parsed, and the states correspond to various stages in the grammar rules. *Note The Bison Parser Algorithm: Algorithm. Grouping A language construct that is (in general) grammatically divisible; for example, `expression' or `declaration' in C. *Note Languages and Context-Free Grammars: Language and Grammar. Infix operator An arithmetic operator that is placed between the operands on which it performs some operation. Input stream A continuous flow of data between devices or programs. Language construct One of the typical usage schemas of the language. For example, one of the constructs of the C language is the `if' statement. *Note Languages and Context-Free Grammars: Language and Grammar. Left associativity Operators having left associativity are analyzed from left to right: `a+b+c' first computes `a+b' and then combines with `c'. *Note Operator Precedence: Precedence. Left recursion A rule whose result symbol is also its first component symbol; for example, `expseq1 : expseq1 ',' exp;'. *Note Recursive Rules: Recursion. Left-to-right parsing Parsing a sentence of a language by analyzing it token by token from left to right. *Note The Bison Parser Algorithm: Algorithm. Lexical analyzer (scanner) A function that reads an input stream and returns tokens one by one. *Note The Lexical Analyzer Function `yylex': Lexical. Lexical tie-in A flag, set by actions in the grammar rules, which alters the way tokens are parsed. *Note Lexical Tie-ins::. Literal string token A token which consists of two or more fixed characters. *Note Symbols::. Look-ahead token A token already read but not yet shifted. *Note Look-Ahead Tokens: Look-Ahead. LALR(1) The class of context-free grammars that Bison (like most other parser generators) can handle; a subset of LR(1). *Note Mysterious Reduce/Reduce Conflicts: Mystery Conflicts. LR(1) The class of context-free grammars in which at most one token of look-ahead is needed to disambiguate the parsing of any piece of input. Nonterminal symbol A grammar symbol standing for a grammatical construct that can be expressed through rules in terms of smaller constructs; in other words, a construct that is not a token. *Note Symbols::. Parse error An error encountered during parsing of an input stream due to invalid syntax. *Note Error Recovery::. Parser A function that recognizes valid sentences of a language by analyzing the syntax structure of a set of tokens passed to it from a lexical analyzer. Postfix operator An arithmetic operator that is placed after the operands upon which it performs some operation. Reduction Replacing a string of nonterminals and/or terminals with a single nonterminal, according to a grammar rule. *Note The Bison Parser Algorithm: Algorithm. Reentrant A reentrant subprogram is a subprogram which can be in invoked any number of times in parallel, without interference between the various invocations. *Note A Pure (Reentrant) Parser: Pure Decl. Reverse polish notation A language in which all operators are postfix operators. Right recursion A rule whose result symbol is also its last component symbol; for example, `expseq1: exp ',' expseq1;'. *Note Recursive Rules: Recursion. Semantics In computer languages, the semantics are specified by the actions taken for each instance of the language, i.e., the meaning of each statement. *Note Defining Language Semantics: Semantics. Shift A parser is said to shift when it makes the choice of analyzing further input from the stream rather than reducing immediately some already-recognized rule. *Note The Bison Parser Algorithm: Algorithm. Single-character literal A single character that is recognized and interpreted as is. *Note From Formal Rules to Bison Input: Grammar in Bison. Start symbol The nonterminal symbol that stands for a complete valid utterance in the language being parsed. The start symbol is usually listed as the first nonterminal symbol in a language specification. *Note The Start-Symbol: Start Decl. Symbol table A data structure where symbol names and associated data are stored during parsing to allow for recognition and use of existing information in repeated uses of a symbol. *Note Multi-function Calc::. Token A basic, grammatically indivisible unit of a language. The symbol that describes a token in the grammar is a terminal symbol. The input of the Bison parser is a stream of tokens which comes from the lexical analyzer. *Note Symbols::. Terminal symbol A grammar symbol that has no rules in the grammar and therefore is grammatically indivisible. The piece of text it represents is a token. *Note Languages and Context-Free Grammars: Language and Grammar.  File: bison.info, Node: Index, Prev: Glossary, Up: Top Index ***** * Menu: * $$: Actions. * $N: Actions. * %expect: Expect Decl. * %left: Using Precedence. * %nonassoc: Using Precedence. * %prec: Contextual Precedence. * %pure_parser: Pure Decl. * %right: Using Precedence. * %start: Start Decl. * %token: Token Decl. * %type: Type Decl. * %union: Union Decl. * @$ <1>: Action Features. * @$: Actions and Locations. * @N <1>: Action Features. * @N: Actions and Locations. * action: Actions. * action data types: Action Types. * action features summary: Action Features. * actions in mid-rule: Mid-Rule Actions. * actions, location: Actions and Locations. * actions, semantic: Semantic Actions. * additional C code section: C Code. * algorithm of parser: Algorithm. * associativity: Why Precedence. * Backus-Naur form: Language and Grammar. * Bison declaration summary: Decl Summary. * Bison declarations: Declarations. * Bison declarations (introduction): Bison Declarations. * Bison grammar: Grammar in Bison. * Bison invocation: Invocation. * Bison parser: Bison Parser. * Bison parser algorithm: Algorithm. * Bison symbols, table of: Table of Symbols. * Bison utility: Bison Parser. * BISON_HAIRY: Environment Variables. * BISON_SIMPLE: Environment Variables. * BNF: Language and Grammar. * C code, section for additional: C Code. * C declarations section: C Declarations. * C-language interface: Interface. * calc: Infix Calc. * calculator, infix notation: Infix Calc. * calculator, multi-function: Multi-function Calc. * calculator, simple: RPN Calc. * character token: Symbols. * compiling the parser: Rpcalc Compile. * conflicts: Shift/Reduce. * conflicts, reduce/reduce: Reduce/Reduce. * conflicts, suppressing warnings of: Expect Decl. * context-dependent precedence: Contextual Precedence. * context-free grammar: Language and Grammar. * controlling function: Rpcalc Main. * dangling else: Shift/Reduce. * data type of locations: Location Type. * data types in actions: Action Types. * data types of semantic values: Value Type. * debugging: Debugging. * declaration summary: Decl Summary. * declarations, Bison: Declarations. * declarations, Bison (introduction): Bison Declarations. * declarations, C: C Declarations. * declaring literal string tokens: Token Decl. * declaring operator precedence: Precedence Decl. * declaring the start symbol: Start Decl. * declaring token type names: Token Decl. * declaring value types: Union Decl. * declaring value types, nonterminals: Type Decl. * default action: Actions. * default data type: Value Type. * default location type: Location Type. * default stack limit: Stack Overflow. * default start symbol: Start Decl. * defining language semantics: Semantics. * else, dangling: Shift/Reduce. * environment variables: Environment Variables. * error: Error Recovery. * error recovery: Error Recovery. * error recovery, simple: Simple Error Recovery. * error reporting function: Error Reporting. * error reporting routine: Rpcalc Error. * examples, simple: Examples. * exercises: Exercises. * file format: Grammar Layout. * finite-state machine: Parser States. * formal grammar: Grammar in Bison. * format of grammar file: Grammar Layout. * glossary: Glossary. * grammar file: Grammar Layout. * grammar rule syntax: Rules. * grammar rules section: Grammar Rules. * grammar, Bison: Grammar in Bison. * grammar, context-free: Language and Grammar. * grouping, syntactic: Language and Grammar. * infix notation calculator: Infix Calc. * interface: Interface. * introduction: Introduction. * invoking Bison: Invocation. * invoking Bison under VMS: VMS Invocation. * LALR(1): Mystery Conflicts. * language semantics, defining: Semantics. * layout of Bison grammar: Grammar Layout. * left recursion: Recursion. * lexical analyzer: Lexical. * lexical analyzer, purpose: Bison Parser. * lexical analyzer, writing: Rpcalc Lexer. * lexical tie-in: Lexical Tie-ins. * literal string token: Symbols. * literal token: Symbols. * location <1>: Locations. * location: Locations Overview. * location actions: Actions and Locations. * look-ahead token: Look-Ahead. * LR(1): Mystery Conflicts. * main function in simple example: Rpcalc Main. * mfcalc: Multi-function Calc. * mid-rule actions: Mid-Rule Actions. * multi-function calculator: Multi-function Calc. * multicharacter literal: Symbols. * mutual recursion: Recursion. * nonterminal symbol: Symbols. * operator precedence: Precedence. * operator precedence, declaring: Precedence Decl. * options for invoking Bison: Invocation. * overflow of parser stack: Stack Overflow. * parse error: Error Reporting. * parser: Bison Parser. * parser stack: Algorithm. * parser stack overflow: Stack Overflow. * parser state: Parser States. * polish notation calculator: RPN Calc. * position, textual <1>: Locations. * position, textual: Locations Overview. * precedence declarations: Precedence Decl. * precedence of operators: Precedence. * precedence, context-dependent: Contextual Precedence. * precedence, unary operator: Contextual Precedence. * preventing warnings about conflicts: Expect Decl. * pure parser: Pure Decl. * recovery from errors: Error Recovery. * recursive rule: Recursion. * reduce/reduce conflict: Reduce/Reduce. * reduction: Algorithm. * reentrant parser: Pure Decl. * reverse polish notation: RPN Calc. * right recursion: Recursion. * rpcalc: RPN Calc. * rule syntax: Rules. * rules section for grammar: Grammar Rules. * running Bison (introduction): Rpcalc Gen. * semantic actions: Semantic Actions. * semantic value: Semantic Values. * semantic value type: Value Type. * shift/reduce conflicts: Shift/Reduce. * shifting: Algorithm. * simple examples: Examples. * single-character literal: Symbols. * stack overflow: Stack Overflow. * stack, parser: Algorithm. * stages in using Bison: Stages. * start symbol: Language and Grammar. * start symbol, declaring: Start Decl. * state (of parser): Parser States. * string token: Symbols. * summary, action features: Action Features. * summary, Bison declaration: Decl Summary. * suppressing conflict warnings: Expect Decl. * symbol: Symbols. * symbol table example: Mfcalc Symtab. * symbols (abstract): Language and Grammar. * symbols in Bison, table of: Table of Symbols. * syntactic grouping: Language and Grammar. * syntax error: Error Reporting. * syntax of grammar rules: Rules. * terminal symbol: Symbols. * textual position <1>: Locations. * textual position: Locations Overview. * token: Language and Grammar. * token type: Symbols. * token type names, declaring: Token Decl. * tracing the parser: Debugging. * unary operator precedence: Contextual Precedence. * using Bison: Stages. * value type, semantic: Value Type. * value types, declaring: Union Decl. * value types, nonterminals, declaring: Type Decl. * value, semantic: Semantic Values. * VMS: VMS Invocation. * warnings, preventing: Expect Decl. * writing a lexical analyzer: Rpcalc Lexer. * YYABORT: Parser Function. * YYACCEPT: Parser Function. * YYBACKUP: Action Features. * yychar: Look-Ahead. * yyclearin: Error Recovery. * yydebug: Debugging. * YYDEBUG: Debugging. * YYEMPTY: Action Features. * yyerrok: Error Recovery. * YYERROR: Action Features. * yyerror: Error Reporting. * YYERROR_VERBOSE: Error Reporting. * YYINITDEPTH: Stack Overflow. * yylex: Lexical. * YYLEX_PARAM: Pure Calling. * yylloc: Token Positions. * YYLLOC_DEFAULT: Location Default Action. * YYLTYPE: Token Positions. * yylval: Token Values. * YYMAXDEPTH: Stack Overflow. * yynerrs: Error Reporting. * yyparse: Parser Function. * YYPARSE_PARAM: Pure Calling. * YYPRINT: Debugging. * YYRECOVERING: Error Recovery. * |: Rules.