doc: use @group to improve page breaking

[bison.git] / doc / bison.texi

diff --git a/doc/bison.texi b/doc/bison.texi
index 912c678233152bf0491fa582e8622778c1777604..39e84e7cb5a01069a3726c28f721bfeb95ee76f5 100644 (file)
--- a/doc/bison.texi
+++ b/doc/bison.texi
@@ -1538,6 +1538,7 @@ calculator.  As in C, comments are placed between @samp{/*@dots{}*/}.
 @example
 /* Reverse polish notation calculator.  */
 
+@group
 %@{
   #define YYSTYPE double
   #include <stdio.h>
@@ -1545,6 +1546,7 @@ calculator.  As in C, comments are placed between @samp{/*@dots{}*/}.
   int yylex (void);
   void yyerror (char const *);
 %@}
+@end group
 
 %token NUM
 
@@ -2411,7 +2413,7 @@ Here are the C and Bison declarations for the multi-function calculator.
 %type  <val>  exp
 
 @group
-%right '='
+%precedence '='
 %left '-' '+'
 %left '*' '/'
 %precedence NEG /* negation--unary minus */
@@ -2857,21 +2859,27 @@ can be done with two @var{Prologue} blocks, one before and one after the
 @code{%union} declaration.
 
 @example
+@group
 %@{
   #define _GNU_SOURCE
   #include <stdio.h>
   #include "ptypes.h"
 %@}
+@end group
 
+@group
 %union @{
   long int n;
   tree t;  /* @r{@code{tree} is defined in @file{ptypes.h}.} */
 @}
+@end group
 
+@group
 %@{
   static void print_token_value (FILE *, int, YYSTYPE);
   #define YYPRINT(F, N, L) print_token_value (F, N, L)
 %@}
+@end group
 
 @dots{}
 @end example
@@ -2903,21 +2911,27 @@ location, or it can be one of @code{requires}, @code{provides},
 Look again at the example of the previous section:
 
 @example
+@group
 %@{
   #define _GNU_SOURCE
   #include <stdio.h>
   #include "ptypes.h"
 %@}
+@end group
 
+@group
 %union @{
   long int n;
   tree t;  /* @r{@code{tree} is defined in @file{ptypes.h}.} */
 @}
+@end group
 
+@group
 %@{
   static void print_token_value (FILE *, int, YYSTYPE);
   #define YYPRINT(F, N, L) print_token_value (F, N, L)
 %@}
+@end group
 
 @dots{}
 @end example
@@ -2969,16 +2983,20 @@ Let's go ahead and add the new @code{YYLTYPE} definition and the
   @} YYLTYPE;
 @}
 
+@group
 %union @{
   long int n;
   tree t;  /* @r{@code{tree} is defined in @file{ptypes.h}.} */
 @}
+@end group
 
+@group
 %code @{
   static void print_token_value (FILE *, int, YYSTYPE);
   #define YYPRINT(F, N, L) print_token_value (F, N, L)
   static void trace_token (enum yytokentype token, YYLTYPE loc);
 @}
+@end group
 
 @dots{}
 @end example
@@ -9716,6 +9734,67 @@ no effect on the conflict report.
 Deprecated constructs whose support will be removed in future versions of
 Bison.
 
+@item precedence
+Useless precedence and associativity directives.  Disabled by default.
+
+Consider for instance the following grammar:
+
+@example
+@group
+%nonassoc "="
+%left "+"
+%left "*"
+%precedence "("
+@end group
+%%
+@group
+stmt:
+  exp
+| "var" "=" exp
+;
+@end group
+
+@group
+exp:
+  exp "+" exp
+| exp "*" "num"
+| "(" exp ")"
+| "num"
+;
+@end group
+@end example
+
+Bison reports:
+
+@c cannot leave the location and the [-Wprecedence] for lack of
+@c width in PDF.
+@example
+@group
+warning: useless precedence and associativity for "="
+ %nonassoc "="
+           ^^^
+@end group
+@group
+warning: useless associativity for "*", use %precedence
+ %left "*"
+       ^^^
+@end group
+@group
+warning: useless precedence for "("
+ %precedence "("
+             ^^^
+@end group
+@end example
+
+One would get the exact same parser with the following directives instead:
+
+@example
+@group
+%left "+"
+%precedence "*"
+@end group
+@end example
+
 @item other
 All warnings not categorized above.  These warnings are enabled by default.
 
@@ -10207,14 +10286,6 @@ therefore, since, as far as we know, @code{double} is the most demanding
 type on all platforms, alignments are enforced for @code{double} whatever
 types are actually used.  This may waste space in some cases.
 
-@item
-Our implementation is not conforming with strict aliasing rules.  Alias
-analysis is a technique used in optimizing compilers to detect when two
-pointers are disjoint (they cannot ``meet'').  Our implementation breaks
-some of the rules that G++ 4.4 uses in its alias analysis, so @emph{strict
-alias analysis must be disabled}.  Use the option
-@option{-fno-strict-aliasing} to compile the generated parser.
-
 @item
 There might be portability issues we are not aware of.
 @end itemize
@@ -11036,7 +11107,7 @@ Finally, we enable scanner tracing.
 
 @comment file: calc++-scanner.ll
 @example
-%option noyywrap nounput batch debug
+%option noyywrap nounput batch debug noinput
 @end example
 
 @noindent