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api.value.type: implement proper support, check, and document

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* data/c.m4 (b4_symbol_type_register, b4_type_define_tag)
(b4_symbol_value_union, b4_value_type_setup_union)
(b4_value_type_setup_variant, b4_value_type_setup):
New.
(b4_value_type_define): Use it to set up properly the type.
Handle the various possible values of api.value.type.
* data/c++.m4 (b4_value_type_declare): Likewise.
* data/lalr1.cc (b4_value_type_setup_variant): Redefine.

* tests/types.at: New.
Exercise all the C/C++ skeletons with different types of
api.value.type values.
* tests/local.mk, tests/testsuite.at: Use it.

* doc/bison.texi (%define Summary): Document api.value.type.
* NEWS: Advertise it, together with api.token.constructor.
This commit is contained in:
Akim Demaille
2013-02-08 17:17:33 +01:00
parent dde95ca432
commit 6574576cfb
9 changed files with 463 additions and 25 deletions
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82
doc/bison.texi
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@@ -5586,6 +5586,7 @@ Summary,,%skeleton}).
Unaccepted @var{variable}s produce an error.
Some of the accepted @var{variable}s are described below.
@c ================================================== api.namespace
@deffn Directive {%define api.namespace} @{@var{namespace}@}
@itemize
@item Languages(s): C++
@@ -5812,14 +5813,89 @@ introduced in Bison 2.8
@deffn Directive {%define api.value.type} @var{type}
@itemize @bullet
@item Language(s):
C++
all
@item Purpose:
Request variant-based semantic values.
The type for semantic values.
@item Accepted Values:
@table @asis
@item @code{""}
This grammar has no semantic value at all. This is not properly supported
yet.
@item @code{%union} (C, C++)
The type is defined thanks to the @code{%union} directive. You don't have
to define @code{api.value.type} in that case, using @code{%union} suffices.
@xref{Union Decl, ,The Collection of Value Types}.
For instance:
@example
%define api.value.type "%union"
%union
@{
int ival;
char *sval;
@}
%token <ival> INT "integer"
%token <sval> STR "string"
@end example
@item @code{union} (C, C++)
The symbols are defined with type names, from which Bison will generate a
@code{union}. For instance:
@example
%define api.value.type "union"
%token <int> INT "integer"
%token <char *> STR "string"
@end example
This feature needs user feedback to stabilize. Note that most C++ objects
cannot be stored in a @code{union}.
@item @code{variant} (C++)
This is similar to @code{union}, but special storage techniques are used to
allow any kind of C++ object to be used. For instance:
@example
%define api.value.type "variant"
%token <int> INT "integer"
%token <std::string> STR "string"
@end example
This feature needs user feedback to stabilize.
@xref{C++ Variants}.
@item any other identifier
Use this name as semantic value.
@example
%code requires
@{
struct my_value
@{
enum
@{
is_int, is_str
@} kind;
union
@{
int ival;
char *sval;
@} u;
@};
@}
%define api.value.type "struct my_value"
%token <u.ival> INT "integer"
%token <u.sval> STR "string"
@end example
@end table
@item Default Value:
FIXME:
@itemize @minus
@item
@code{%union} if @code{%union} is used, otherwise @dots{}
@item
@code{int} if type tags are used (i.e., @samp{%token <@var{type}>@dots{}} or
@samp{%token <@var{type}>@dots{}} is used), otherwise @dots{}
@item
@code{""}
@end itemize
@item History:
introduced in Bison 2.8. Was introduced for Java only in 2.3b as
@code{stype}.