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, 1 insertions, 1 deletions

diff --git a/parser.l b/parser.l
index 8536a01e..e310d1f7 100644
--- a/parser.l
+++ b/parser.l
@@ -607,7 +607,7 @@ UONLY   {U2}{U}|{U3}{U}{U}|{U4}{U}{U}{U}
 
 <NESTED,BRACED,QSPECIAL>@ {
   yylval->lineno = yyextra->lineno;
-  return yytext[0];
+  return (opt_compat && opt_compat <= 248) ? OLD_AT : '@';
 }
 
 <NESTED,QSPECIAL,BRACED>,[*] {