X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/69991a58278c6af21590fcc52b58d6eb44d0552f..fdbcd8e28930c6a1e6d4f80636c7b4e21a575489:/TODO

diff --git a/TODO b/TODO
index 0b12b008..7514df80 100644
--- a/TODO
+++ b/TODO
@@ -1,5 +1,51 @@
 -*- 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;
+	}
+
+* Language independent actions
+
+Currently bison, the generator, transforms $1, $$ and so forth into
+direct C code, manipulating the stacks.  This is problematic, because
+(i) it means that if we want more languages, we need to update the
+generator, and (ii), it forces names everywhere (e.g., the C++
+skeleton would be happy to use other naming schemes, and actually,
+even other accessing schemes).
+
+Therefore we want
+
+1. the generator to replace $1, etc. by M4 macro invocations
+   (b4_dollar(1), b4_at(3), b4_dollar_dollar) etc.
+
+2. the skeletons to define these macros.
+
+But currently the actions are double-quoted, to protect them from M4
+evaluation.  So we need to:
+
+3. stop quoting them
+
+4. change the [ and ] in the actions into @<:@ and @:>@
+
+5. extend the postprocessor to maps these back onto [ and ].
+
 * Coding system independence
 Paul notes:
 
@@ -33,16 +79,6 @@ Paul suggests:
    #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 +207,6 @@ 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 +214,6 @@ 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.
@@ -400,7 +401,7 @@ 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));