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NEWS: named constructors are preferable to symbol_type ctors

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Reported by Frank Heckenbach.
http://lists.gnu.org/archive/html/bug-bison/2019-01/msg00043.html
This commit is contained in:
Akim Demaille
2019-02-03 09:32:12 +01:00
parent cacdfc2f6e
commit 03878edf77
1 changed files with 12 additions and 11 deletions
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23
NEWS
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@@ -223,17 +223,18 @@ GNU Bison NEWS
symbol_type (int token, const int&);
symbol_type (int token);
which should be used in a Flex-scanner as follows.
%%
[a-z]+ return yy::parser::symbol_type (ID, yytext);
[0-9]+ return yy::parser::symbol_type (INT, text_to_int (yytext);
":" return yy::parser::symbol_type (’:’);
<<EOF>> return yy::parser::symbol_type (0);
Correct matching between token types and value types is checked via
'assert'. For instance, 'symbol_type (ID, 42)' would abort (while
'make_ID (42)' would not even compile).
'assert'; for instance, 'symbol_type (ID, 42)' would abort. Named
constructors are preferable, as they offer better type safety (for
instance 'make_ID (42)' would not even compile), but symbol_type
constructors may help when token types are discovered at run-time, e.g.,
[a-z]+ {
if (auto i = lookup_keyword (yytext))
return yy::parser::symbol_type (i);
else
return yy::parser::make_ID (yytext);
}
*** C++: Variadic emplace
@@ -3486,7 +3487,7 @@ along with this program. If not, see <http://www.gnu.org/licenses/>.
LocalWords: Heimbigner AST src ast Makefile srcdir MinGW xxlex XXSTYPE
LocalWords: XXLTYPE strictfp IDEs ffixit fdiagnostics parseable fixits
LocalWords: Wdeprecated yytext Variadic variadic yyrhs yyphrs RCS README
LocalWords: noexcept constexpr ispell american
LocalWords: noexcept constexpr ispell american deprecations
Local Variables:
ispell-dictionary: "american"