user-defined function on the resulting values to produce an arbitrary
merged result.
-Let's consider an example, vastly simplified from C++.
+Let's consider an example, vastly simplified from a C++ grammar.
@example
%@{
| decl %dprec 2
;
-expr : ID @{ printf ("%s ", $$); @}
+expr : ID @{ printf ("%s ", $$); @}
| TYPENAME '(' expr ')'
- @{ printf ("%s <cast> ", $1); @}
- | expr '+' expr @{ printf ("+ "); @}
- | expr '=' expr @{ printf ("= "); @}
+ @{ printf ("%s <cast> ", $1); @}
+ | expr '+' expr @{ printf ("+ "); @}
+ | expr '=' expr @{ printf ("= "); @}
;
decl : TYPENAME declarator ';'
- @{ printf ("%s <declare> ", $1); @}
+ @{ printf ("%s <declare> ", $1); @}
| TYPENAME declarator '=' expr ';'
- @{ printf ("%s <init-declare> ", $1); @}
+ @{ printf ("%s <init-declare> ", $1); @}
;
-declarator : ID @{ printf ("\"%s\" ", $1); @}
+declarator : ID @{ printf ("\"%s\" ", $1); @}
| '(' declarator ')'
;
@end example
#include <stdio.h>
void
-yyerror (const char *s) /* called by yyparse on error */
+yyerror (const char *s) /* Called by yyparse on error. */
@{
printf ("%s\n", s);
@}
@group
void
-yyerror (const char *s) /* Called by yyparse on error */
+yyerror (const char *s) /* Called by yyparse on error. */
@{
printf ("%s\n", s);
@}
Rename the external symbols used in the parser so that they start with
@var{prefix} instead of @samp{yy}. The precise list of symbols renamed
is @code{yyparse}, @code{yylex}, @code{yyerror}, @code{yynerrs},
-@code{yylval}, @code{yychar}, @code{yydebug}, and possible
-@code{yylloc}. For example, if you use @samp{%name-prefix="c_"}, the
-names become @code{c_parse}, @code{c_lex}, and so on. @xref{Multiple
-Parsers, ,Multiple Parsers in the Same Program}.
+@code{yylval}, @code{yylloc}, @code{yychar}, @code{yydebug}, and
+possible @code{yylloc}. For example, if you use
+@samp{%name-prefix="c_"}, the names become @code{c_parse}, @code{c_lex},
+and so on. @xref{Multiple Parsers, ,Multiple Parsers in the Same
+Program}.
@item %no-parser
Do not include any C code in the parser file; generate tables only. The
names that do not conflict.
The precise list of symbols renamed is @code{yyparse}, @code{yylex},
-@code{yyerror}, @code{yynerrs}, @code{yylval}, @code{yychar} and
-@code{yydebug}. For example, if you use @samp{-p c}, the names become
-@code{cparse}, @code{clex}, and so on.
+@code{yyerror}, @code{yynerrs}, @code{yylval}, @code{yylloc},
+@code{yychar} and @code{yydebug}. For example, if you use @samp{-p c},
+the names become @code{cparse}, @code{clex}, and so on.
@strong{All the other variables and macros associated with Bison are not
renamed.} These others are not global; there is no conflict if the same
write an action which directs @code{yyparse} to return immediately
without reading further.
+
+@deftypefun int yyparse (void)
The value returned by @code{yyparse} is 0 if parsing was successful (return
is due to end-of-input).
The value is 1 if parsing failed (return is due to a syntax error).
+@end deftypefun
In an action, you can cause immediate return from @code{yyparse} by using
these macros:
-@table @code
-@item YYACCEPT
+@defmac YYACCEPT
@findex YYACCEPT
Return immediately with value 0 (to report success).
+@end defmac
-@item YYABORT
+@defmac YYABORT
@findex YYABORT
Return immediately with value 1 (to report failure).
-@end table
+@end defmac
+
+If you use a reentrant parser, you can optionally pass additional
+parameter information to it in a reentrant way. To do so, use the
+declaration @code{%parse-param}:
+
+@deffn {Directive} %parse-param @var{argument-declaration} @var{argument-name}
+@findex %parse-param
+Declare that @code{argument-name} is an additional @code{yyparse}
+argument. This argument is also passed to @code{yyerror}. The
+@var{argument-declaration} is used when declaring functions or
+prototypes.
+@end deffn
+
+Here's an example. Write this in the parser:
+
+@example
+%parse-param "int *nastiness" "nastiness"
+%parse-param "int *randomness" "randomness"
+@end example
+
+@noindent
+Then call the parser like this:
+
+@example
+@{
+ int nastiness, randomness;
+ @dots{} /* @r{Store proper data in @code{nastiness} and @code{randomness}.} */
+ value = yyparse (&nastiness, &randomness);
+ @dots{}
+@}
+@end example
+
+@noindent
+In the grammar actions, use expressions like this to refer to the data:
+
+@example
+exp: @dots{} @{ @dots{}; *randomness += 1; @dots{} @}
+@end example
+
@node Lexical
@section The Lexical Analyzer Function @code{yylex}
this case, omit the second argument; @code{yylex} will be called with
only one argument.
-@vindex YYPARSE_PARAM
-If you use a reentrant parser, you can optionally pass additional
-parameter information to it in a reentrant way. To do so, define the
-macro @code{YYPARSE_PARAM} as a variable name. This modifies the
-@code{yyparse} function to accept one argument, of type @code{void *},
-with that name.
-
-When you call @code{yyparse}, pass the address of an object, casting the
-address to @code{void *}. The grammar actions can refer to the contents
-of the object by casting the pointer value back to its proper type and
-then dereferencing it. Here's an example. Write this in the parser:
-@example
-%@{
-struct parser_control
-@{
- int nastiness;
- int randomness;
-@};
+If you wish to pass the additional parameter data to @code{yylex}, use
+@code{%lex-param} just like @code{%parse-param} (@pxref{Parser
+Function}).
-#define YYPARSE_PARAM parm
-%@}
-@end example
+@deffn {Directive} lex-param @var{argument-declaration} @var{argument-name}
+@findex %lex-param
+Declare that @code{argument-name} is an additional @code{yylex}
+argument.
+@end deffn
-@noindent
-Then call the parser like this:
+For instance:
@example
-struct parser_control
-@{
- int nastiness;
- int randomness;
-@};
-
-@dots{}
-
-@{
- struct parser_control foo;
- @dots{} /* @r{Store proper data in @code{foo}.} */
- value = yyparse ((void *) &foo);
- @dots{}
-@}
+%parse-param "int *nastiness" "nastiness"
+%lex-param "int *nastiness" "nastiness"
+%parse-param "int *randomness" "randomness"
@end example
@noindent
-In the grammar actions, use expressions like this to refer to the data:
+results in the following signature:
@example
-((struct parser_control *) parm)->randomness
+int yylex (int *nastiness);
+int yyparse (int *nastiness, int *randomness);
@end example
-@vindex YYLEX_PARAM
-If you wish to pass the additional parameter data to @code{yylex},
-define the macro @code{YYLEX_PARAM} just like @code{YYPARSE_PARAM}, as
-shown here:
+If @code{%pure-parser} is added:
@example
-%@{
-struct parser_control
-@{
- int nastiness;
- int randomness;
-@};
-
-#define YYPARSE_PARAM parm
-#define YYLEX_PARAM parm
-%@}
+int yylex (YYSTYPE *lvalp, int *nastiness);
+int yyparse (int *nastiness, int *randomness);
@end example
-You should then define @code{yylex} to accept one additional
-argument---the value of @code{parm}. (This makes either two or three
-arguments in total, depending on whether an argument of type
-@code{YYLTYPE} is passed.) You can declare the argument as a pointer to
-the proper object type, or you can declare it as @code{void *} and
-access the contents as shown above.
+@noindent
+and finally, if both @code{%pure-parser} and @code{%locations} are used:
-You can use @samp{%pure-parser} to request a reentrant parser without
-also using @code{YYPARSE_PARAM}. Then you should call @code{yyparse}
-with no arguments, as usual.
+@example
+int yylex (YYSTYPE *lvalp, YYLTYPE *llocp, int *nastiness);
+int yyparse (int *nastiness, int *randomness);
+@end example
@node Error Reporting
@section The Error Reporting Function @code{yyerror}
receives one argument. For a parse error, the string is normally
@w{@code{"parse error"}}.
-@findex YYERROR_VERBOSE
-If you define the macro @code{YYERROR_VERBOSE} in the Bison declarations
-section (@pxref{Bison Declarations, ,The Bison Declarations Section}),
-then Bison provides a more verbose and specific error message string
-instead of just plain @w{@code{"parse error"}}. It doesn't matter what
-definition you use for @code{YYERROR_VERBOSE}, just whether you define
-it.
+@findex %error-verbose
+If you invoke the directive @code{%error-verbose} in the Bison
+declarations section (@pxref{Bison Declarations, ,The Bison Declarations
+Section}), then Bison provides a more verbose and specific error message
+string instead of just plain @w{@code{"parse error"}}.
The parser can detect one other kind of error: stack overflow. This
happens when the input contains constructions that are very deeply
@example
@group
void
-yyerror (char *s)
+yyerror (const char *s)
@{
@end group
@group
(@pxref{Error Recovery}). If recovery is impossible, @code{yyparse} will
immediately return 1.
+Obviously, in location tracking pure parsers, @code{yyerror} should have
+an access to the current location. This is indeed the case for the GLR
+parsers, but not for the Yacc parser, for historical reasons. I.e., if
+@samp{%locations %pure-parser} is passed then the prototypes for
+@code{yyerror} are:
+
+@example
+void yyerror (const char *msg); /* Yacc parsers. */
+void yyerror (YYLTYPE *locp, const char *msg); /* GLR parsers. */
+@end example
+
+If @samp{%parse-param "int *nastiness" "nastiness"} is used, then:
+
+@example
+void yyerror (int *randomness, const char *msg); /* Yacc parsers. */
+void yyerror (int *randomness, const char *msg); /* GLR parsers. */
+@end example
+
+Finally, GLR and Yacc parsers share the same @code{yyerror} calling
+convention for absolutely pure parsers, i.e., when the calling
+convention of @code{yylex} @emph{and} the calling convention of
+@code{%pure-parser} are pure. I.e.:
+
+@example
+/* Location tracking. */
+%locations
+/* Pure yylex. */
+%pure-parser
+%lex-param "int *nastiness" "nastiness"
+/* Pure yyparse. */
+%parse-param "int *nastiness" "nastiness"
+%parse-param "int *randomness" "randomness"
+@end example
+
+@noindent
+results in the following signatures for all the parser kinds:
+
+@example
+int yylex (YYSTYPE *lvalp, YYLTYPE *llocp, int *nastiness);
+int yyparse (int *nastiness, int *randomness);
+void yyerror (YYLTYPE *locp,
+ int *nastiness, int *randomness,
+ const char *msg);
+@end example
+
+@noident
+Please, note that the prototypes are only indications of how the code
+produced by Bison will use @code{yyerror}, but you still have freedom
+and the exit value, and even on making @code{yyerror} a variadic
+function. It is precisely to enable this that the message is passed
+last.
+
@vindex yynerrs
The variable @code{yynerrs} contains the number of syntax errors
encountered so far. Normally this variable is global; but if you
$accept -> . exp $ (rule 0)
- NUM shift, and go to state 1
+ NUM shift, and go to state 1
- exp go to state 2
+ exp go to state 2
@end example
This reads as follows: ``state 0 corresponds to being at the very
exp -> NUM . (rule 5)
- $default reduce using rule 5 (exp)
+ $default reduce using rule 5 (exp)
@end example
@noindent
exp -> exp . '*' exp (rule 3)
exp -> exp . '/' exp (rule 4)
- $ shift, and go to state 3
- '+' shift, and go to state 4
- '-' shift, and go to state 5
- '*' shift, and go to state 6
- '/' shift, and go to state 7
+ $ shift, and go to state 3
+ '+' shift, and go to state 4
+ '-' shift, and go to state 5
+ '*' shift, and go to state 6
+ '/' shift, and go to state 7
@end example
@noindent
$accept -> exp $ . (rule 0)
- $default accept
+ $default accept
@end example
@noindent
exp -> exp '+' . exp (rule 1)
- NUM shift, and go to state 1
+ NUM shift, and go to state 1
- exp go to state 8
+ exp go to state 8
state 5
exp -> exp '-' . exp (rule 2)
- NUM shift, and go to state 1
+ NUM shift, and go to state 1
- exp go to state 9
+ exp go to state 9
state 6
exp -> exp '*' . exp (rule 3)
- NUM shift, and go to state 1
+ NUM shift, and go to state 1
- exp go to state 10
+ exp go to state 10
state 7
exp -> exp '/' . exp (rule 4)
- NUM shift, and go to state 1
+ NUM shift, and go to state 1
- exp go to state 11
+ exp go to state 11
@end example
As was announced in beginning of the report, @samp{State 8 contains 1
exp -> exp . '*' exp (rule 3)
exp -> exp . '/' exp (rule 4)
- '*' shift, and go to state 6
- '/' shift, and go to state 7
+ '*' shift, and go to state 6
+ '/' shift, and go to state 7
- '/' [reduce using rule 1 (exp)]
- $default reduce using rule 1 (exp)
+ '/' [reduce using rule 1 (exp)]
+ $default reduce using rule 1 (exp)
@end example
Indeed, there are two actions associated to the lookahead @samp{/}:
exp -> exp . '*' exp (rule 3)
exp -> exp . '/' exp (rule 4)
- '*' shift, and go to state 6
- '/' shift, and go to state 7
+ '*' shift, and go to state 6
+ '/' shift, and go to state 7
- '/' [reduce using rule 2 (exp)]
- $default reduce using rule 2 (exp)
+ '/' [reduce using rule 2 (exp)]
+ $default reduce using rule 2 (exp)
state 10
exp -> exp '*' exp . (rule 3)
exp -> exp . '/' exp (rule 4)
- '/' shift, and go to state 7
+ '/' shift, and go to state 7
- '/' [reduce using rule 3 (exp)]
- $default reduce using rule 3 (exp)
+ '/' [reduce using rule 3 (exp)]
+ $default reduce using rule 3 (exp)
state 11
exp -> exp . '/' exp (rule 4)
exp -> exp '/' exp . (rule 4)
- '+' shift, and go to state 4
- '-' shift, and go to state 5
- '*' shift, and go to state 6
- '/' shift, and go to state 7
+ '+' shift, and go to state 4
+ '-' shift, and go to state 5
+ '*' shift, and go to state 6
+ '/' shift, and go to state 7
- '+' [reduce using rule 4 (exp)]
- '-' [reduce using rule 4 (exp)]
- '*' [reduce using rule 4 (exp)]
- '/' [reduce using rule 4 (exp)]
- $default reduce using rule 4 (exp)
+ '+' [reduce using rule 4 (exp)]
+ '-' [reduce using rule 4 (exp)]
+ '*' [reduce using rule 4 (exp)]
+ '/' [reduce using rule 4 (exp)]
+ $default reduce using rule 4 (exp)
@end example
@noindent
@code{yyparse} return 1. @xref{Error Recovery}.
@item YYERROR_VERBOSE
-Macro that you define with @code{#define} in the Bison declarations
-section to request verbose, specific error message strings when
-@code{yyerror} is called.
+An obsolete macro that you define with @code{#define} in the Bison
+declarations section to request verbose, specific error message strings
+when @code{yyerror} is called. It doesn't matter what definition you
+use for @code{YYERROR_VERBOSE}, just whether you define it. Using
+@code{%error-verbose} is preferred.
@item YYINITDEPTH
Macro for specifying the initial size of the parser stack.
@xref{Stack Overflow}.
@item YYLEX_PARAM
-Macro for specifying an extra argument (or list of extra arguments) for
-@code{yyparse} to pass to @code{yylex}. @xref{Pure Calling,, Calling
-Conventions for Pure Parsers}.
+An obsolete macro for specifying an extra argument (or list of extra
+arguments) for @code{yyparse} to pass to @code{yylex}. he use of this
+macro is deprecated, and is supported only for Yacc like parsers.
+@xref{Pure Calling,, Calling Conventions for Pure Parsers}.
@item YYLTYPE
Macro for the data type of @code{yylloc}; a structure with four
@xref{Stack Overflow}.
@item YYPARSE_PARAM
-Macro for specifying the name of a parameter that @code{yyparse} should
-accept. @xref{Pure Calling,, Calling Conventions for Pure Parsers}.
+An obsolete macro for specifying the name of a parameter that
+@code{yyparse} should accept. The use of this macro is deprecated, and
+is supported only for Yacc like parsers. @xref{Pure Calling,, Calling
+Conventions for Pure Parsers}.
@item YYRECOVERING
Macro whose value indicates whether the parser is recovering from a
time to resolve reduce/reduce conflicts. @xref{GLR Parsers, ,Writing
@acronym{GLR} Parsers}.
+@item %error-verbose
+Bison declaration to request verbose, specific error message strings
+when @code{yyerror} is called.
+
@item %file-prefix="@var{prefix}"
Bison declaration to set the prefix of the output files. @xref{Decl
Summary}.
Bison declaration to assign left associativity to token(s).
@xref{Precedence Decl, ,Operator Precedence}.
+@item %lex-param "@var{argument-declaration}" "@var{argument-name}"
+Bison declaration to specifying an additional parameter that
+@code{yylex} should accept. @xref{Pure Calling,, Calling Conventions
+for Pure Parsers}.
+
@item %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
Bison declaration to set the name of the parser file. @xref{Decl
Summary}.
+@item %parse-param "@var{argument-declaration}" "@var{argument-name}"
+Bison declaration to specifying an additional parameter that
+@code{yyparse} should accept. @xref{Parser Function,, The Parser
+Function @code{yyparse}}.
+
@item %prec
Bison declaration to assign a precedence to a specific rule.
@xref{Contextual Precedence, ,Context-Dependent Precedence}.
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