@value{UPDATED}), the @acronym{GNU} parser generator.
Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1995, 1998,
-1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
+1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 Free Software
+Foundation, Inc.
@quotation
Permission is granted to copy, distribute and/or modify this document
(a) below. A copy of the license is included in the section entitled
``@acronym{GNU} Free Documentation License.''
-(a) The @acronym{FSF}'s Back-Cover Text is: ``You have freedom to copy
-and modify this @acronym{GNU} Manual, like @acronym{GNU} software.
-Copies published by the Free Software Foundation raise funds for
-@acronym{GNU} development.''
+(a) The FSF's Back-Cover Text is: ``You have the freedom to copy and
+modify this @acronym{GNU} manual. Buying copies from the @acronym{FSF}
+supports it in developing @acronym{GNU} and promoting software
+freedom.''
@end quotation
@end copying
Precedence}.
You can explicitly specify the numeric code for a token type by appending
-a decimal or hexadecimal integer value in the field immediately
+a nonnegative decimal or hexadecimal integer value in the field immediately
following the token name:
@example
interchangeably in further declarations or the grammar rules. The
@code{yylex} function can use the token name or the literal string to
obtain the token type code number (@pxref{Calling Convention}).
+Syntax error messages passed to @code{yyerror} from the parser will reference
+the literal string instead of the token name.
+
+The token numbered as 0 corresponds to end of file; the following line
+allows for nicer error messages referring to ``end of file'' instead
+of ``$end'':
+
+@example
+%token END 0 "end of file"
+@end example
@node Precedence Decl
@subsection Operator Precedence
@xref{Precedence, ,Operator Precedence}, for general information on
operator precedence.
-The syntax of a precedence declaration is the same as that of
+The syntax of a precedence declaration is nearly the same as that of
@code{%token}: either
@example
the one declared later has the higher precedence and is grouped first.
@end itemize
+For backward compatibility, there is a confusing difference between the
+argument lists of @code{%token} and precedence declarations.
+Only a @code{%token} can associate a literal string with a token type name.
+A precedence declaration always interprets a literal string as a reference to a
+separate token.
+For example:
+
+@example
+%left OR "<=" // Does not declare an alias.
+%left OR 134 "<=" 135 // Declares 134 for OR and 135 for "<=".
+@end example
+
@node Union Decl
@subsection The Collection of Value Types
@cindex declaring value types
@cindex push parser
@findex %define api.push_pull
+(The current push parsing interface is experimental and may evolve.
+More user feedback will help to stabilize it.)
+
A pull parser is called once and it takes control until all its input
is completely parsed. A push parser, on the other hand, is called
each time a new token is made available.
@item Purpose: Requests a pull parser, a push parser, or both.
@xref{Push Decl, ,A Push Parser}.
+(The current push parsing interface is experimental and may evolve.
+More user feedback will help to stabilize it.)
@item Accepted Values: @code{"pull"}, @code{"push"}, @code{"both"}
@deffn {Directive} %language "@var{language}"
Specify the programming language for the generated parser. Currently
-supported languages include C and C++.
+supported languages include C, C++, and Java.
@var{language} is case-insensitive.
@end deffn
@section The Push Parser Function @code{yypush_parse}
@findex yypush_parse
+(The current push parsing interface is experimental and may evolve.
+More user feedback will help to stabilize it.)
+
You call the function @code{yypush_parse} to parse a single token. This
function is available if either the @code{%define api.push_pull "push"} or
@code{%define api.push_pull "both"} declaration is used.
@section The Pull Parser Function @code{yypull_parse}
@findex yypull_parse
+(The current push parsing interface is experimental and may evolve.
+More user feedback will help to stabilize it.)
+
You call the function @code{yypull_parse} to parse the rest of the input
stream. This function is available if the @code{%define api.push_pull "both"}
declaration is used.
@section The Parser Create Function @code{yystate_new}
@findex yypstate_new
+(The current push parsing interface is experimental and may evolve.
+More user feedback will help to stabilize it.)
+
You call the function @code{yypstate_new} to create a new parser instance.
This function is available if either the @code{%define api.push_pull "push"} or
@code{%define api.push_pull "both"} declaration is used.
@deftypefun yypstate *yypstate_new (void)
The fuction will return a valid parser instance if there was memory available
-or NULL if no memory was available.
+or 0 if no memory was available.
+In impure mode, it will also return 0 if a parser instance is currently
+allocated.
@end deftypefun
@node Parser Delete Function
@section The Parser Delete Function @code{yystate_delete}
@findex yypstate_delete
+(The current push parsing interface is experimental and may evolve.
+More user feedback will help to stabilize it.)
+
You call the function @code{yypstate_delete} to delete a parser instance.
function is available if either the @code{%define api.push_pull "push"} or
@code{%define api.push_pull "both"} declaration is used.
The next section reports useless tokens, nonterminal and rules. Useless
nonterminals and rules are removed in order to produce a smaller parser,
but useless tokens are preserved, since they might be used by the
-scanner (note the difference between ``useless'' and ``not used''
+scanner (note the difference between ``useless'' and ``unused''
below):
@example
-Useless nonterminals:
+Nonterminals useless in grammar:
useless
-Terminals which are not used:
+Terminals unused in grammar:
STR
Rules useless in grammar:
like @samp{%glr-parser}, Bison might not be Yacc-compatible even if
this option is specified.
+@item -W
+@itemx --warnings
+Output warnings falling in @var{category}. @var{category} can be one
+of:
+@table @code
+@item midrule-values
+Warn about mid-rule values that are set but not used within any of the actions
+of the parent rule.
+For example, warn about unused @code{$2} in:
+
+@example
+exp: '1' @{ $$ = 1; @} '+' exp @{ $$ = $1 + $4; @};
+@end example
+
+Also warn about mid-rule values that are used but not set.
+For example, warn about unset @code{$$} in the mid-rule action in:
+
+@example
+ exp: '1' @{ $1 = 1; @} '+' exp @{ $$ = $2 + $4; @};
+@end example
+
+These warnings are not enabled by default since they sometimes prove to
+be false alarms in existing grammars employing the Yacc constructs
+@code{$0} or @code{$-@var{n}} (where @var{n} is some positive integer).
+
+
+@item yacc
+Incompatibilities with @acronym{POSIX} Yacc.
+
+@item all
+All the warnings.
+@item none
+Turn off all the warnings.
+@item error
+Treat warnings as errors.
+@end table
+
+A category can be turned off by prefixing its name with @samp{no-}. For
+instance, @option{-Wno-syntax} will hide the warnings about unused
+variables.
@end table
@noindent
@itemx --language=@var{language}
Specify the programming language for the generated parser, as if
@code{%language} was specified (@pxref{Decl Summary, , Bison Declaration
-Summary}). Currently supported languages include C and C++.
+Summary}). Currently supported languages include C, C++, and Java.
@var{language} is case-insensitive.
@item --locations
Adjust the output:
@table @option
-@item -d
-@itemx --defines
+@item --defines[=@var{file}]
Pretend that @code{%defines} was specified, i.e., write an extra output
file containing macro definitions for the token type names defined in
the grammar, as well as a few other declarations. @xref{Decl Summary}.
-@item --defines=@var{defines-file}
-Same as above, but save in the file @var{defines-file}.
+@item -d
+This is the same as @code{--defines} except @code{-d} does not accept a
+@var{file} argument since POSIX Yacc requires that @code{-d} can be bundled
+with other short options.
@item -b @var{file-prefix}
@itemx --file-prefix=@var{prefix}
The other output files' names are constructed from @var{file} as
described under the @samp{-v} and @samp{-d} options.
-@item -g
+@item -g[@var{file}]
+@itemx --graph[=@var{file}]
Output a graphical representation of the @acronym{LALR}(1) grammar
automaton computed by Bison, in @uref{http://www.graphviz.org/, Graphviz}
@uref{http://www.graphviz.org/doc/info/lang.html, @acronym{DOT}} format.
-If the grammar file is @file{foo.y}, the output file will
-be @file{foo.dot}.
-
-@item --graph=@var{graph-file}
-The behavior of @var{--graph} is the same than @samp{-g}. The only
-difference is that it has an optional argument which is the name of
-the output graph file.
+@code{@var{file}} is optional.
+If omitted and the grammar file is @file{foo.y}, the output file will be
+@file{foo.dot}.
+
+@item -x[@var{file}]
+@itemx --xml[=@var{file}]
+Output an XML report of the @acronym{LALR}(1) automaton computed by Bison.
+@code{@var{file}} is optional.
+If omitted and the grammar file is @file{foo.y}, the output file will be
+@file{foo.xml}.
+(The current XML schema is experimental and may evolve.
+More user feedback will help to stabilize it.)
@end table
@node Option Cross Key
@c - %language "Java"
@c - initial action
+(The current Java interface is experimental and may evolve.
+More user feedback will help to stabilize it.)
+
The Java parser skeletons are selected using a language directive,
@samp{%language "Java"}, or the synonymous command-line option
@option{--language=java}.
The parser class defines an inner class, @code{Location}, that is used
for location tracking. If the parser is pure, it also defines an
-inner interface, @code{Lexer}; see~@ref{Java Scanner Interface} for the
+inner interface, @code{Lexer}; see @ref{Java Scanner Interface} for the
meaning of pure parsers when the Java language is chosen. Other than
-these inner class/interface, and the members described in~@ref{Java
+these inner class/interface, and the members described in @ref{Java
Parser Interface}, all the other members and fields are preceded
with a @code{yy} prefix to avoid clashes with user code.
state of the parser is always local to an instance of the parser class.
Therefore, all Java parsers are ``pure'', and the @code{%pure-parser}
directive does not do anything when used in Java.
+@c FIXME: But a bit farther it is stated that
+@c If @code{%pure-parser} is not specified, the lexer interface
+@c resides in the same class (@code{YYParser}) as the Bison-generated
+@c parser. The fields and methods that are provided to
+@c this end are as follows.
The scanner always resides in a separate class than the parser.
-Still, Java also two possible ways to interface a Bison-generated Java
+Still, there are two possible ways to interface a Bison-generated Java
parser with a scanner, that is, the scanner may reside in a separate file
than the Bison grammar, or in the same file. The interface
to the scanner is similar in the two cases.
specify them with @code{%lex-param}; they are passed before
@code{%parse-param}s to the constructor.
-In the second case, the scanner has to implement interface @code{Lexer},
+In the second case, the scanner has to implement the @code{Lexer} interface,
which is defined within the parser class (e.g., @code{YYParser.Lexer}).
The constructor of the parser object will then accept an object
implementing the interface; @code{%lex-param} is not used in this
@end deftypemethod
@deftypemethod {Lexer} {Object} getLVal ()
-Return respectively the first position of the last token that yylex
-returned, and the first position beyond it.
+Return the semantical value of the last token that yylex returned.
The return type can be changed using @samp{%define "stype"
"@var{class-name}".}
The fields and methods that are provided to this end are as follows.
@deftypemethod {YYParser} {void} error (Location @var{l}, String @var{m})
-As explained in @pxref{Java Parser Interface}, this method is defined
+As already explained (@pxref{Java Parser Interface}), this method is defined
by the user to emit an error message. The first parameter is not used
unless location tracking is active. Its type can be changed using
@samp{%define "location_type" "@var{class-name}".}
call this function to delete the memory associated with a parser.
@xref{Parser Delete Function, ,The Parser Delete Function
@code{yypstate_delete}}.
+(The current push parsing interface is experimental and may evolve.
+More user feedback will help to stabilize it.)
@end deffn
@deffn {Function} yypstate_new
call this function to create a new parser.
@xref{Parser Create Function, ,The Parser Create Function
@code{yypstate_new}}.
+(The current push parsing interface is experimental and may evolve.
+More user feedback will help to stabilize it.)
@end deffn
@deffn {Function} yypull_parse
parse the rest of the input stream.
@xref{Pull Parser Function, ,The Pull Parser Function
@code{yypull_parse}}.
+(The current push parsing interface is experimental and may evolve.
+More user feedback will help to stabilize it.)
@end deffn
@deffn {Function} yypush_parse
The parser function produced by Bison in push mode; call this function to
parse a single token. @xref{Push Parser Function, ,The Push Parser Function
@code{yypush_parse}}.
+(The current push parsing interface is experimental and may evolve.
+More user feedback will help to stabilize it.)
@end deffn
@deffn {Macro} YYPARSE_PARAM
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