Remove a dead item.

[bison.git] / TODO

diff --git a/TODO b/TODO
index fd0d4f7084e19c4672d0e771b0dd330ecda6ee68..434053356856d2c91172cf5695b273c7f16c0e89 100644 (file)
--- a/TODO
+++ b/TODO
@@ -45,6 +45,46 @@ 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:
 
@@ -78,16 +118,6 @@ 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: