* doc/bison.texinfo (Initial Action Decl): New.

[bison.git] / doc / bison.texinfo

diff --git a/doc/bison.texinfo b/doc/bison.texinfo
index dd2407a39c8c17585a2fdd4e6dd666ad8030df8e..e2706921fbc66ddcd3d5b7bde3c008fe3dd3ed2d 100644 (file)
--- a/doc/bison.texinfo
+++ b/doc/bison.texinfo
@@ -228,6 +228,7 @@ Bison Declarations
 * Precedence Decl::   Declaring terminals with precedence and associativity.
 * Union Decl::        Declaring the set of all semantic value types.
 * Type Decl::         Declaring the choice of type for a nonterminal symbol.
 * Precedence Decl::   Declaring terminals with precedence and associativity.
 * Union Decl::        Declaring the set of all semantic value types.
 * Type Decl::         Declaring the choice of type for a nonterminal symbol.

+* Initial Action Decl::  Code run before parsing starts.

 * Destructor Decl::   Declaring how symbols are freed.
 * Expect Decl::       Suppressing warnings about parsing conflicts.
 * Start Decl::        Specifying the start symbol.
 * Destructor Decl::   Declaring how symbols are freed.
 * Expect Decl::       Suppressing warnings about parsing conflicts.
 * Start Decl::        Specifying the start symbol.


@@ -3520,6 +3521,7 @@ Grammars}).
 * Precedence Decl::   Declaring terminals with precedence and associativity.
 * Union Decl::        Declaring the set of all semantic value types.
 * Type Decl::         Declaring the choice of type for a nonterminal symbol.
 * Precedence Decl::   Declaring terminals with precedence and associativity.
 * Union Decl::        Declaring the set of all semantic value types.
 * Type Decl::         Declaring the choice of type for a nonterminal symbol.

+* Initial Action Decl::  Code run before parsing starts.

 * Destructor Decl::   Declaring how symbols are freed.
 * Expect Decl::       Suppressing warnings about parsing conflicts.
 * Start Decl::        Specifying the start symbol.
 * Destructor Decl::   Declaring how symbols are freed.
 * Expect Decl::       Suppressing warnings about parsing conflicts.
 * Start Decl::        Specifying the start symbol.


@@ -3729,6 +3731,22 @@ use the same @code{<@var{type}>} construction in a declaration for the
 terminal symbol.  All kinds of token declarations allow
 @code{<@var{type}>}.
 
 terminal symbol.  All kinds of token declarations allow
 @code{<@var{type}>}.
 

+@node Initial Action Decl
+@subsection Performing Actions before Parsing
+@findex %initial-action
+
+Sometimes your parser needs to perform some initializations before
+parsing.  The @code{%initial-action} directive allows for such arbitrary
+code.
+
+@deffn {Directive} %initial-action @{ @var{code} @}
+@findex %initial-action
+Declare that the @var{code} must be invoked before parsing each time
+@code{yyparse} is called.  The @var{code} may use @code{@@$} to
+designate the initial location, and the @code{%parse-param}.
+@end deffn
+
+

 @node Destructor Decl
 @subsection Freeing Discarded Symbols
 @cindex freeing discarded symbols
 @node Destructor Decl
 @subsection Freeing Discarded Symbols
 @cindex freeing discarded symbols


@@ -7144,6 +7162,10 @@ time to resolve reduce/reduce conflicts.  @xref{GLR Parsers, ,Writing
 @acronym{GLR} Parsers}.
 @end deffn
 
 @acronym{GLR} Parsers}.
 @end deffn
 

+@deffn {Directive} %initial-action
+Run user code before parsing.  @xref{Initial Action Decl, , Performing Actions before Parsing}.
+@end deffn
+

 @deffn {Directive} %error-verbose
 Bison declaration to request verbose, specific error message strings
 when @code{yyerror} is called.
 @deffn {Directive} %error-verbose
 Bison declaration to request verbose, specific error message strings
 when @code{yyerror} is called.