X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Fmathql%2Fgrammar.txt;h=5622761a3381db959570f04bbd778f456bc1d31f;hb=4167cea65ca58897d1a3dbb81ff95de5074700cc;hp=abbda194ed939277c3d7524bb8806473627cbfc7;hpb=c6b9538995874c6595874e88bc7bf8965e50f14b;p=helm.git

diff --git a/helm/mathql/grammar.txt b/helm/mathql/grammar.txt
index abbda194e..5622761a3 100644
--- a/helm/mathql/grammar.txt
+++ b/helm/mathql/grammar.txt
@@ -57,7 +57,8 @@ MATHEMATICAL QUERY LANGUAGE (MathQL)
 						  insiemi stringhe *)
        |  EX <bool>			       (* existential on attributes
 						  of references *)
-<string-set> := {}				   (* insieme vuoto*)
+<string-set> := ( <string-set> )               (* parentesizzazione *)
+             |  {}			       (* insieme vuoto*)
 	     |  <quoted-constant-string>       (* stringa singoletto *)
              |  {<quoted-constant-string-list>}(* insieme stringhe *)
              |  REFOF <set>		       (* insieme riferimenti *)