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* doc/autoconf.texi: Document @$.

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(Locations): New section.
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Akim Demaille
2001-08-01 17:49:14 +00:00
parent 73975f004c
commit 847bf1f538
11 changed files with 579 additions and 275 deletions
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@@ -1,5 +1,5 @@
Ceci est le fichier Info bison.info, produit par Makeinfo version 4.0 à
partir bison.texinfo.
Ceci est le fichier Info bison.info, produit par Makeinfo version 4.0b
à partir bison.texinfo.
START-INFO-DIR-ENTRY
* bison: (bison). GNU Project parser generator (yacc replacement).
@@ -263,7 +263,6 @@ GNU GENERAL PUBLIC LICENSE
**************************
Version 2, June 1991
Copyright (C) 1989, 1991 Free Software Foundation, Inc.
59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
@@ -322,7 +321,6 @@ patent must be licensed for everyone's free use or not licensed at all.
modification follow.
TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
0. This License applies to any program or other work which contains a
notice placed by the copyright holder saying it may be distributed
under the terms of this General Public License. The "Program",
@@ -639,6 +637,7 @@ carefully.
a semantic value (the value of an integer,
the name of an identifier, etc.).
* Semantic Actions:: Each rule can have an action containing C code.
* Locations Overview:: Tracking Locations.
* Bison Parser:: What are Bison's input and output,
how is the output used?
* Stages:: Stages in writing and running Bison grammars.
@@ -830,7 +829,7 @@ programming language, an expression typically has a semantic value that
is a tree structure describing the meaning of the expression.

File: bison.info, Node: Semantic Actions, Next: Bison Parser, Prev: Semantic Values, Up: Concepts
File: bison.info, Node: Semantic Actions, Next: Locations Overview, Prev: Semantic Values, Up: Concepts
Semantic Actions
================
@@ -859,7 +858,38 @@ The action says how to produce the semantic value of the sum expression
from the values of the two subexpressions.

File: bison.info, Node: Bison Parser, Next: Stages, Prev: Semantic Actions, Up: Concepts
File: bison.info, Node: Locations Overview, Next: Bison Parser, Prev: Semantic Actions, Up: Concepts
Locations
=========
Many applications, like interpreters or compilers, have to produce
verbose and useful error messages. To achieve this, one must be able to
keep track of the "textual position", or "location", of each syntactic
construct. Bison provides a mechanism for handling these locations.
Each token has a semantic value. In a similar fashion, each token
has an associated location, but the type of locations is the same for
all tokens and groupings. Moreover, the output parser is equipped with
a default data structure for storing locations (*note Locations::, for
more details).
Like semantic values, locations can be reached in actions using a
dedicated set of constructs. In the example above, the location of the
whole grouping is `@$', while the locations of the subexpressions are
`@1' and `@3'.
When a rule is matched, a default action is used to compute the
semantic value of its left hand side (*note Actions::). In the same
way, another default action is used for locations. However, the action
for locations is general enough for most cases, meaning there is
usually no need to describe for each rule how `@$' should be formed.
When building a new location for a given grouping, the default behavior
of the output parser is to take the beginning of the first symbol, and
the end of the last symbol.

File: bison.info, Node: Bison Parser, Next: Stages, Prev: Locations Overview, Up: Concepts
Bison Output: the Parser File
=============================
@@ -1029,45 +1059,3 @@ extension is a convention used for Bison input files.
* Gen: Rpcalc Gen. Running Bison on the grammar file.
* Comp: Rpcalc Compile. Run the C compiler on the output code.

File: bison.info, Node: Rpcalc Decls, Next: Rpcalc Rules, Up: RPN Calc
Declarations for `rpcalc'
-------------------------
Here are the C and Bison declarations for the reverse polish notation
calculator. As in C, comments are placed between `/*...*/'.
/* Reverse polish notation calculator. */
%{
#define YYSTYPE double
#include <math.h>
%}
%token NUM
%% /* Grammar rules and actions follow */
The C declarations section (*note The C Declarations Section: C
Declarations.) contains two preprocessor directives.
The `#define' directive defines the macro `YYSTYPE', thus specifying
the C data type for semantic values of both tokens and groupings (*note
Data Types of Semantic Values: Value Type.). The Bison parser will use
whatever type `YYSTYPE' is defined as; if you don't define it, `int' is
the default. Because we specify `double', each token and each
expression has an associated value, which is a floating point number.
The `#include' directive is used to declare the exponentiation
function `pow'.
The second section, Bison declarations, provides information to
Bison about the token types (*note The Bison Declarations Section:
Bison Declarations.). Each terminal symbol that is not a
single-character literal must be declared here. (Single-character
literals normally don't need to be declared.) In this example, all the
arithmetic operators are designated by single-character literals, so the
only terminal symbol that needs to be declared is `NUM', the token type
for numeric constants.