More.

[bison.git] / TODO

diff --git a/TODO b/TODO
index 0b12b008c33436f4d0f134378230e1b6af3c1380..1c7c9f77f2bb62c9b23254e9fa695c873db3a767 100644 (file)
--- a/TODO
+++ b/TODO
@@ -1,5 +1,26 @@
 -*- outline -*-
 
+* Several %unions
+I think this is a pleasant (but useless currently) feature, but in the
+future, I want a means to %include other bits of grammars, and _then_
+it will be important for the various bits to define their needs in
+%union.
+
+When implementing multiple-%union support, bare the following in mind:
+
+- when --yacc, this must be flagged as an error.  Don't make it fatal
+  though.
+
+- The #line must now appear *inside* the definition of yystype.
+  Something like
+
+       {
+       #line 12 "foo.y"
+         int ival;
+       #line 23 "foo.y"
+         char *sval;
+       }
+
 * Coding system independence
 Paul notes:
 
@@ -13,36 +34,6 @@ Paul notes:
        PDP-10 ports :-) but they should probably be documented
        somewhere.
 
-* Using enums instead of int for tokens.
-Paul suggests:
-
-   #ifndef YYTOKENTYPE
-   # if defined (__STDC__) || defined (__cplusplus)
-      /* Put the tokens into the symbol table, so that GDB and other debuggers
-         know about them.  */
-      enum yytokentype {
-        FOO = 256,
-        BAR,
-        ...
-      };
-      /* POSIX requires `int' for tokens in interfaces.  */
-   #  define YYTOKENTYPE int
-   # endif
-   #endif
-   #define FOO 256
-   #define BAR 257
-   ...
-
-> I'm in favor of
->
-> %token FOO 256
-> %token BAR 257
->
-> and Bison moves error into 258.
-
-Yes, I think that's a valid extension too, if the user doesn't define
-the token number for error.
-
 * Output directory
 Akim:
 
@@ -171,40 +162,6 @@ critical for user data: when aborting a parsing, when handling the
 error token etc., we often throw away yylval without giving a chance
 of cleaning it up to the user.
 
-* NEWS
-Sort from 1.31 NEWS.
-
-* Prologue
-The %union is declared after the user C declarations. It can be
-a problem if YYSTYPE is declared after the user part.  []
-
-Actually, the real problem seems that the %union ought to be output
-where it was defined.  For instance, in gettext/intl/plural.y, we
-have:
-
-       %{
-       ...
-       #include "gettextP.h"
-       ...
-       %}
-
-       %union {
-         unsigned long int num;
-         enum operator op;
-         struct expression *exp;
-       }
-
-       %{
-       ...
-       static int yylex PARAMS ((YYSTYPE *lval, const char **pexp));
-       ...
-       %}
-
-Where the first part defines struct expression, the second uses it to
-define YYSTYPE, and the last uses YYSTYPE.  Only this order is valid.
-
-Note that we have the same problem with GCC.
-
 * --graph
 Show reductions.       []
 
@@ -212,7 +169,6 @@ Show reductions.    []
 ** %no-lines           [ok]
 ** %no-parser          []
 ** %pure-parser                []
-** %semantic-parser    []
 ** %token-table                []
 ** Options which could use parse_dquoted_param ().
 Maybe transfered in lex.c.
@@ -313,8 +269,13 @@ It is unfortunate that there is a total order for precedence.  It
 makes it impossible to have modular precedence information.  We should
 move to partial orders.
 
+This will be possible with a Bison parser for the grammar, as it will
+make it much easier to extend the grammar.
+
 * Parsing grammars
-Rewrite the reader in Bison.
+Rewrite the reader in Flex/Bison.  There will be delicate parts, in
+particular, expect the scanner to be hard to write.  Many interesting
+features cannot be implemented without such a new reader.
 
 * Problems with aliases
 From: "Baum, Nathan I" <s0009525@chelt.ac.uk>
@@ -362,7 +323,6 @@ everything, but the -v mode only tells you what you need for examining
 conflicts? (Or, perhaps, a "*** This state has N conflicts ***" marker above
 each state with conflicts.)
 
-
 * $undefined
 From Hans:
 - If the Bison generated parser experiences an undefined number in the
@@ -385,6 +345,21 @@ $<type_name>$ = $<type_name>1. I therefore think that one should implement
 a Bison option where every typed default rule is explicitly written out
 (same typed ruled can of course be grouped together).
 
+Note: Robert Anisko handles this.  He knows how to do it.
+
+* Documenting C++ output
+Write a first documentation for C++ output.
+
+* Warnings
+It would be nice to have warning support.  See how Autoconf handles
+them, it is fairly well described there.  It would be very nice to
+implement this in such a way that other programs could use
+lib/warnings.[ch].
+
+Don't work on this without first announcing you do, as I already have
+thought about it, and know many of the components that can be used to
+implement it.
+
 * Pre and post actions.
 From: Florian Krohm <florian@edamail.fishkill.ibm.com>
 Subject: YYACT_EPILOGUE
@@ -400,7 +375,7 @@ The way I solved this was to define a macro YYACT_EPILOGUE that would
 be invoked after the action. For reasons of symmetry I also added
 YYACT_PROLOGUE. Although I had no use for that I can envision how it
 might come in handy for debugging purposes.
-All is needed is to add 
+All is needed is to add
 
 #if YYLSP_NEEDED
     YYACT_EPILOGUE (yyval, (yyvsp - yylen), yylen, yyloc, (yylsp - yylen));