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60 Bison 2.3 See Section 8.2 [Tracing Your Parser], page 95. %defines [Directive] Write a header file containing macro definitions for the token type names defined in the grammar as well as a few other declarations. If the parser output file is named ‘name.c’ then this file is named ‘name.h’. Unless YYSTYPE is already defined as a macro, the output header declares YYSTYPE. Therefore, if you are using a %union (see Section 3.5.2 [More Than One Value Type], page 46) with components that require other definitions, or if you have defined a YYSTYPE macro (see Section 3.5.1 [Data Types of Semantic Values], page 46), you need to arrange for these definitions to be propagated to all modules, e.g., by putting them in a prerequisite header that is included both by your parser and by any other module that needs YYSTYPE. Unless your parser is pure, the output header declares yylval as an external variable. See Section 3.7.10 [A Pure (Reentrant) Parser], page 58. If you have also used locations, the output header declares YYLTYPE and yylloc using a protocol similar to that of YYSTYPE and yylval. See Section 3.6 [Tracking Locations], page 51. This output file is normally essential if you wish to put the definition of yylex in a separate source file, because yylex typically needs to be able to refer to the abovementioned declarations and to the token type codes. See Section 4.2.2 [Semantic Values of Tokens], page 65. %destructor [Directive] Specify how the parser should reclaim the memory associated to discarded symbols. See Section 3.7.7 [Freeing Discarded Symbols], page 57. %file-prefix="prefix" [Directive] Specify a prefix to use for all Bison output file names. The names are chosen as if the input file were named ‘prefix.y’. %locations [Directive] Generate the code processing the locations (see Section 4.4 [Special Features for Use in Actions], page 68). This mode is enabled as soon as the grammar uses the special ‘@n’ tokens, but if your grammar does not use it, using ‘%locations’ allows for more accurate syntax error messages. %name-prefix="prefix" [Directive] Rename the external symbols used in the parser so that they start with prefix instead of ‘yy’. The precise list of symbols renamed in C parsers is yyparse, yylex, yyerror, yynerrs, yylval, yychar, yydebug, and (if locations are used) yylloc. For example, if you use ‘%name-prefix="c_"’, the names become c_parse, c_lex, and so on. In C++ parsers, it is only the surrounding namespace which is named prefix instead of ‘yy’. See Section 3.8 [Multiple Parsers in the Same Program], page 62. %no-parser [Directive] Do not include any C code in the parser file; generate tables only. The parser file contains just #define directives and static variable declarations.
Chapter 3: Bison Grammar Files 61 This option also tells Bison to write the C code for the grammar actions into a file named ‘file.act’, in the form of a brace-surrounded body fit for a switch statement. %no-lines [Directive] Don’t generate any #line preprocessor commands in the parser file. Ordinarily Bison writes these commands in the parser file so that the C compiler and debuggers will associate errors and object code with your source file (the grammar file). This directive causes them to associate errors with the parser file, treating it an independent source file in its own right. %output="file" Specify file for the parser file. [Directive] %pure-parser [Directive] Request a pure (reentrant) parser program (see Section 3.7.10 [A Pure (Reentrant) Parser], page 58). %require "version" [Directive] Require version version or higher of Bison. See Section 3.7.1 [Require a Version of Bison], page 54. %token-table [Directive] Generate an array of token names in the parser file. The name of the array is yytname; yytname[i] is the name of the token whose internal Bison token code number is i. The first three elements of yytname correspond to the predefined tokens "$end", "error", and "$undefined"; after these come the symbols defined in the grammar file. The name in the table includes all the characters needed to represent the token in Bison. For single-character literals and literal strings, this includes the surrounding quoting characters and any escape sequences. For example, the Bison single-character literal ’+’ corresponds to a three-character name, represented in C as "’+’"; and the Bison two-character literal string "\\/" corresponds to a five-character name, represented in C as "\"\\\\/\"". When you specify %token-table, Bison also generates macro definitions for macros YYNTOKENS, YYNNTS, and YYNRULES, and YYNSTATES: YYNTOKENS YYNNTS YYNRULES YYNSTATES The highest token number, plus one. The number of nonterminal symbols. The number of grammar rules, The number of parser states (see Section 5.5 [Parser States], page 75). %verbose [Directive] Write an extra output file containing verbose descriptions of the parser states and what is done for each type of look-ahead token in that state. See Section 8.1 [Understanding Your Parser], page 89, for more information.
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Bison The Yacc-compatible Parser Ge
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i Table of Contents Introduction .
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4 Parser C-Language Interface . . .
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Introduction 1 Introduction Bison i
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Conditions for Using Bison 3 Condit
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Appendix B: Glossary 123 Appendix B
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Appendix C: Copying This Manual 127
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Index 135 Index $ $$ . . . . . . .
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Index 137 LALR(1) grammars . . . .
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