X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/e141f4d4bb6584bfbf13003047a2e48e9a6eab6a..16d94f45c9be6a569147fa160993ffe41f8b0b2f:/TODO?ds=sidebyside

diff --git a/TODO b/TODO
index d9221b0e..588bf468 100644
--- a/TODO
+++ b/TODO
@@ -118,59 +118,15 @@ so both 256 and 257 are "mysterious".
 ** YYFAIL
 It is seems to be *really* obsolete now, shall we remove it?
 
-** YYBACKUP
-There is no test about it, no examples in the doc, and I'm not sure
-what it should look like.  For instance what follows crashes.
-
-  %error-verbose
-  %debug
-  %pure-parser
-  %code {
-  # include <stdio.h>
-  # include <stdlib.h>
-  # include <assert.h>
-
-    static void yyerror (const char *msg);
-    static int yylex (YYSTYPE *yylval);
-  }
-  %%
-  exp:
-    'a'   { printf ("a: %d\n", $1); }
-  | 'b'   { YYBACKUP('a', 123); }
-  ;
-  %%
-  static int
-  yylex (YYSTYPE *yylval)
-  {
-    static char const input[] = "b";
-    static size_t toknum;
-    assert (toknum < sizeof input);
-    *yylval = (toknum + 1) * 10;
-    return input[toknum++];
-  }
-
-  static void
-  yyerror (const char *msg)
-  {
-    fprintf (stderr, "%s\n", msg);
-  }
-
-  int
-  main (void)
-  {
-    yydebug = !!getenv("YYDEBUG");
-    return yyparse ();
-  }
-
 ** yychar == yyempty_
 The code in yyerrlab reads:
 
       if (yychar <= YYEOF)
-	{
-	  /* Return failure if at end of input.  */
-	  if (yychar == YYEOF)
-	    YYABORT;
-	}
+        {
+          /* Return failure if at end of input.  */
+          if (yychar == YYEOF)
+            YYABORT;
+        }
 
 There are only two yychar that can be <= YYEOF: YYEMPTY and YYEOF.
 But I can't produce the situation where yychar is YYEMPTY here, is it
@@ -251,36 +207,11 @@ DeRemer and Penello: they already provide the algorithm.
 
 * Extensions
 
-** Labeling the symbols
-Have a look at the Lemon parser generator: instead of $1, $2 etc. they
-can name the values.  This is much more pleasant.  For instance:
-
-       exp (res): exp (a) '+' exp (b) { $res = $a + $b; };
-
-I love this.  I have been bitten too often by the removal of the
-symbol, and forgetting to shift all the $n to $n-1.  If you are
-unlucky, it compiles...
-
-But instead of using $a etc., we can use regular variables.  And
-instead of using (), I propose to use `:' (again).  Paul suggests
-supporting `->' in addition to `:' to separate LHS and RHS. In other
-words:
-
-       r:exp -> a:exp '+' b:exp { r = a + b; };
-
-That requires an significant improvement of the grammar parser.  Using
-GLR would be nice.  It also requires that Bison know the type of the
-symbols (which will be useful for %include anyway).  So we have some
-time before...
-
-Note that there remains the problem of locations: `@r'?
-
-
 ** $-1
 We should find a means to provide an access to values deep in the
 stack.  For instance, instead of
 
-	baz: qux { $$ = $<foo>-1 + $<bar>0 + $1; }
+        baz: qux { $$ = $<foo>-1 + $<bar>0 + $1; }
 
 we should be able to have:
 
@@ -313,13 +244,13 @@ XML output for GNU Bison
 * Unit rules
 Maybe we could expand unit rules, i.e., transform
 
-	exp: arith | bool;
-	arith: exp '+' exp;
-	bool: exp '&' exp;
+        exp: arith | bool;
+        arith: exp '+' exp;
+        bool: exp '&' exp;
 
 into
 
-	exp: exp '+' exp | exp '&' exp;
+        exp: exp '+' exp | exp '&' exp;
 
 when there are no actions.  This can significantly speed up some
 grammars.  I can't find the papers.  In particular the book `LR
@@ -344,19 +275,19 @@ Wow, %printer is not documented.  Clearly mark YYPRINT as obsolete.
 * Coding system independence
 Paul notes:
 
-	Currently Bison assumes 8-bit bytes (i.e. that UCHAR_MAX is
-	255).  It also assumes that the 8-bit character encoding is
-	the same for the invocation of 'bison' as it is for the
-	invocation of 'cc', but this is not necessarily true when
-	people run bison on an ASCII host and then use cc on an EBCDIC
-	host.  I don't think these topics are worth our time
-	addressing (unless we find a gung-ho volunteer for EBCDIC or
-	PDP-10 ports :-) but they should probably be documented
-	somewhere.
+        Currently Bison assumes 8-bit bytes (i.e. that UCHAR_MAX is
+        255).  It also assumes that the 8-bit character encoding is
+        the same for the invocation of 'bison' as it is for the
+        invocation of 'cc', but this is not necessarily true when
+        people run bison on an ASCII host and then use cc on an EBCDIC
+        host.  I don't think these topics are worth our time
+        addressing (unless we find a gung-ho volunteer for EBCDIC or
+        PDP-10 ports :-) but they should probably be documented
+        somewhere.
 
-	More importantly, Bison does not currently allow NUL bytes in
-	tokens, either via escapes (e.g., "x\0y") or via a NUL byte in
-	the source code.  This should get fixed.
+        More importantly, Bison does not currently allow NUL bytes in
+        tokens, either via escapes (e.g., "x\0y") or via a NUL byte in
+        the source code.  This should get fixed.
 
 * --graph
 Show reductions.
@@ -474,7 +405,7 @@ Here's a proposal for how a new implementation might look:
 
 -----
 
-Copyright (C) 2001-2004, 2006, 2008-2010 Free Software Foundation, Inc.
+Copyright (C) 2001-2004, 2006, 2008-2012 Free Software Foundation, Inc.
 
 This file is part of Bison, the GNU Compiler Compiler.