four members:
@example
-struct
+typedef struct YYLTYPE
@{
int first_line;
int first_column;
int last_line;
int last_column;
-@}
+@} YYLTYPE;
@end example
@node Actions and Locations
locations are much more general than semantic values, there is room in
the output parser to redefine the default action to take for each
rule. The @code{YYLLOC_DEFAULT} macro is invoked each time a rule is
-matched, before the associated action is run.
+matched, before the associated action is run. It is also invoked
+while processing a syntax error, to compute the error's location.
Most of the time, this macro is general enough to suppress location
dedicated code from semantic actions.
The @code{YYLLOC_DEFAULT} macro takes three parameters. The first one is
-the location of the grouping (the result of the computation). The second one
-is an array holding locations of all right hand side elements of the rule
-being matched. The last one is the size of the right hand side rule.
+the location of the grouping (the result of the computation). When a
+rule is matched, the second parameter is an array holding locations of
+all right hand side elements of the rule being matched, and the third
+parameter is the size of the rule's right hand side. When processing
+a syntax error, the second parameter is an array holding locations of
+the symbols that were discarded during error processing, and the third
+parameter is the number of discarded symbols.
-By default, it is defined this way for simple @acronym{LALR}(1) parsers:
+By default, @code{YYLLOC_DEFAULT} is defined this way for simple
+@acronym{LALR}(1) parsers:
@example
@group
in the @code{%token} and @code{%type} declarations to pick one of the types
for a terminal or nonterminal symbol (@pxref{Type Decl, ,Nonterminal Symbols}).
-Note that, unlike making a @code{union} declaration in C, you do not write
+As an extension to @acronym{POSIX}, a tag is allowed after the
+@code{union}. For example:
+
+@example
+@group
+%union value @{
+ double val;
+ symrec *tptr;
+@}
+@end group
+@end example
+
+specifies the union tag @code{value}, so the corresponding C type is
+@code{union value}. If you do not specify a tag, it defaults to
+@code{YYSTYPE}.
+
+Note that, unlike making a @code{union} declaration in C, you need not write
a semicolon after the closing brace.
@node Type Decl
(@pxref{Parser Function, , The Parser Function @code{yyparse}}).
@strong{Warning:} as of Bison 1.875, this feature is still considered as
-experimental, as there was not enough users feedback. In particular,
+experimental, as there was not enough user feedback. In particular,
the syntax might still change.
@end deffn
Generate an array of token names in the parser file. The name of the
array is @code{yytname}; @code{yytname[@var{i}]} is the name of the
token whose internal Bison token code number is @var{i}. The first
-three elements of @code{yytname} are always @code{"$end"},
+three elements of @code{yytname} correspond to the predefined tokens
+@code{"$end"},
@code{"error"}, and @code{"$undefined"}; after these come the symbols
defined in the grammar file.
grammar, in particular, it is only slightly slower than with the default
Bison parser.
+For a more detailed exposition of GLR parsers, please see: Elizabeth
+Scott, Adrian Johnstone and Shamsa Sadaf Hussain, Tomita-Style
+Generalised @acronym{LR} Parsers, Royal Holloway, University of
+London, Department of Computer Science, TR-00-12,
+@uref{http://www.cs.rhul.ac.uk/research/languages/publications/tomita_style_1.ps},
+(2000-12-24).
+
@node Stack Overflow
@section Stack Overflow, and How to Avoid It
@cindex stack overflow
@example
calc.y: warning: 1 useless nonterminal and 1 useless rule
calc.y:11.1-7: warning: useless nonterminal: useless
-calc.y:11.8-12: warning: useless rule: useless: STR
-calc.y contains 7 shift/reduce conflicts.
+calc.y:11.10-12: warning: useless rule: useless: STR
+calc.y: conflicts: 7 shift/reduce
@end example
When given @option{--report=state}, in addition to @file{calc.tab.c}, it
The next section lists states that still have conflicts.
@example
-State 8 contains 1 shift/reduce conflict.
-State 9 contains 1 shift/reduce conflict.
-State 10 contains 1 shift/reduce conflict.
-State 11 contains 4 shift/reduce conflicts.
+State 8 conflicts: 1 shift/reduce
+State 9 conflicts: 1 shift/reduce
+State 10 conflicts: 1 shift/reduce
+State 11 conflicts: 4 shift/reduce
@end example
@noindent
exp go to state 11
@end example
-As was announced in beginning of the report, @samp{State 8 contains 1
-shift/reduce conflict}:
+As was announced in beginning of the report, @samp{State 8 conflicts:
+1 shift/reduce}:
@example
state 8
@xref{Pure Calling,, Calling Conventions for Pure Parsers}.
@end deffn
-@deffn {Macro} YYLTYPE
-Macro for the data type of @code{yylloc}; a structure with four
+@deffn {Type} YYLTYPE
+Data type of @code{yylloc}; by default, a structure with four
members. @xref{Location Type, , Data Types of Locations}.
@end deffn
-@deffn {Type} yyltype
-Default value for YYLTYPE.
-@end deffn
-
@deffn {Macro} YYMAXDEPTH
Macro for specifying the maximum size of the parser stack. @xref{Stack
Overflow}.
to anything else.
@end deffn
-@deffn {Macro} YYSTYPE
-Macro for the data type of semantic values; @code{int} by default.
+@deffn {Type} YYSTYPE
+Data type of semantic values; @code{int} by default.
@xref{Value Type, ,Data Types of Semantic Values}.
@end deffn
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