Future/bison
1
0
Fork 0
mirror of https://git.savannah.gnu.org/git/bison.git synced 2026-03-09 20:33:03 +00:00
Code Issues Packages Projects Releases Wiki Activity

doc: glr: document typed mergers

Browse Source 
See <https://lists.gnu.org/r/help-bison/2020-12/msg00016.html>.

* doc/bison.texi (Merging GLR Parses): document typed mergers.
And avoid #define YYSTYPE.
This commit is contained in:
Akim Demaille
2021-08-04 09:06:56 +02:00
parent cb7bdc251d
commit 413d318940
2 changed files with 44 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
TODO
View File

@@ -28,15 +28,6 @@ the out-of-range new values, we need something like doubling the size.
** glr ** glr
There is no test with "Parse on stack %ld rejected by rule %d" in it. There is no test with "Parse on stack %ld rejected by rule %d" in it.
** %merge
Tests with typed %merge: 716 717 718 740 741 742 746 747 748
716: Duplicate representation of merged trees: glr.c FAILED (glr-regression.at:517)
740: Leaked semantic values if user action cuts parse: glr.c FAILED (glr-regression.at:1230)
746: Incorrect lookahead during nondeterministic GLR: glr.c FAILED (glr-regression.at:1610)
Document typed merges.
** yyrline etc. ** yyrline etc.
Clarify that rule numbers in the skeletons are 1-based. Clarify that rule numbers in the skeletons are 1-based.

46
doc/bison.texi
View File

@@ -1167,11 +1167,12 @@ Let's consider an example, vastly simplified from a C++ grammar.
@example @example
%@{ %@{
#include <stdio.h> #include <stdio.h>
#define YYSTYPE char const *
int yylex (void); int yylex (void);
void yyerror (char const *); void yyerror (char const *);
%@} %@}
%define api.value.type @{char const *@}
%token TYPENAME ID %token TYPENAME ID
%right '=' %right '='
@@ -1302,7 +1303,6 @@ in the C declarations at the beginning of the file:
@example @example
%@{ %@{
#define YYSTYPE char const *
static YYSTYPE stmtMerge (YYSTYPE x0, YYSTYPE x1); static YYSTYPE stmtMerge (YYSTYPE x0, YYSTYPE x1);
%@} %@}
@end example @end example
@@ -1321,6 +1321,48 @@ productions that participate in any particular merge have identical
and the parser will report an error during any parse that results in and the parser will report an error during any parse that results in
the offending merge. the offending merge.
@sp 1
The signature of the merger depends on the type of the symbol. In the
previous example, the merged-to symbol (@code{stmt}) does not have a
specific type, and the merger is
@example
YYSTYPE stmtMerge (YYSTYPE x0, YYSTYPE x1);
@end example
@noindent
However, if @code{stmt} had a declared type, e.g.,
@example
%type <Node *> stmt;
@end example
@noindent
or
@example
@group
%union @{
Node *node;
...
@};
@end group
%type <node> stmt;
@end example
@noindent
then the prototype of the merger must be:
@example
Node *stmtMerge (YYSTYPE x0, YYSTYPE x1);
@end example
@noindent
(This signature might be a mistake originally, and maybe it should have been
@samp{Node *stmtMerge (Node *x0, Node *x1)}. If you have an opinion about
it, please let us know.)
@node GLR Semantic Actions @node GLR Semantic Actions
@subsection GLR Semantic Actions @subsection GLR Semantic Actions