parser: fix bad precedence of @ token.

Whereas @a..@b parses and transforms to (rcons @a @a),
@(a)..@(a) goes to @(rcons a @(a)).

* parser.l (grammar): Under 248 compatibility or lower, the @
character now produces the OLD_AT token. Otherwise it produces
the '@' character, as before.

* parser.y (OLD_AT): New token replaces the '@' at the old
low precedence position. '@' is now at the highest precedence,
together with OLD_DOTDOT.  (We don't care about interactions
between '@' and OLD_DOTDOT, because OLD_DOTDOT only exists in
185 compatibility, in which '@' is OLD_AT).
(meta): The two rules have to be unfortunately duplicated for
OLD_AT, since there is no BNF OR operator in Yacc.

* txr.1: Compat note added.

* lex.yy.c.shipped: Updated.

* y.tab.c.shipped, y.tab.h.shipped: Likewise.

1 files changed, 13 insertions, 3 deletions

diff --git a/parser.y b/parser.y
index 21b6945d..661200dd 100644
--- a/parser.y
+++ b/parser.y
@@ -125,7 +125,7 @@ INLINE val expand_form_ver(val form, int ver)
 %token <val> NUMBER METANUM
 %token <val> HASH_N_EQUALS HASH_N_HASH
 
-%token <chr> REGCHAR REGTOKEN LITCHAR SPLICE
+%token <chr> REGCHAR REGTOKEN LITCHAR SPLICE OLD_AT
 %token <chr> CONSDOT LAMBDOT UREFDOT OREFDOT UOREFDOT
 
 %type <val> spec hash_semi_or_n_expr hash_semi_or_i_expr
@@ -160,13 +160,13 @@ INLINE val expand_form_ver(val form, int ver)
 %right OUTPUT REPEAT REP FIRST LAST EMPTY DEFINE IF ELIF ELSE
 %right SPACE TEXT NUMBER METANUM HASH_N_EQUALS HASH_N_HASH HASH_B_QUOTE
 %nonassoc '[' ']' '(' ')'
-%left '-' ',' '\'' '^' SPLICE '@'
+%left '-' ',' '\'' '^' SPLICE OLD_AT
 %left '|' '/'
 %left '&'
 %right '~' '*' '?' '+' '%'
 %right DOTDOT
 %right '.' CONSDOT LAMBDOT UREFDOT OREFDOT UOREFDOT REGCHAR REGTOKEN LITCHAR
-%right OLD_DOTDOT
+%right OLD_DOTDOT '@'
 
 %%
 
@@ -954,6 +954,15 @@ meta : '@' n_expr               { if (consp($2))
                                   yybadtok(yychar, lit("meta expression")); }
      ;
 
+meta : OLD_AT n_expr            { if (consp($2))
+                                    $$ = rl(cons(expr_s, cons($2, nil)), num($1));
+                                  else
+                                    $$ = rl(cons(var_s, cons($2, nil)),
+                                            num($1)); }
+     | OLD_AT error             { $$ = nil;
+                                  yybadtok(yychar, lit("meta expression")); }
+     ;
+
 dwim : '[' '.' n_exprs ']'      { val a = car($3);
                                   val ur = uref_helper(parser, a);
                                   $$ = rlcp_tree(cons(dwim_s,
@@ -1989,6 +1998,7 @@ void yybadtoken(parser_t *parser, int tok, val context)
   case WSPLICE: problem = lit("#*\""); break;
   case QWORDS:         problem = lit("#`"); break;
   case QWSPLICE:       problem = lit("#*`"); break;
+  case OLD_AT:         problem = lit("@"); break;
   }
 
   if (problem != 0)