Changes between Version 4 and Version 5 of Taskforces/FCS/FCS-QL

Timestamp:

08/05/15 12:32:26 (9 years ago)

Author:

peter.beinema@mpi.nl

Comment:

--

Taskforces/FCS/FCS-QL

@@ -108 +108 @@
  * regex are not defined/guarded by this grammar :/
  * non-continuous rule numbers are currently intended; we've already removed some. Rules will be renumbered, when grammar is fixed.
+== Discussion ==
+Peter Beinema, MPI, proposes some minor changes to the grammar:
+ * main query [2] / simple query [3]: above definition generate structural ambiguity. Not a problem for ANTLR (which selects the right-recursive solution), but some other parser generators generate all solutions - which are exponential wrt the number of main queries. I propose to use the alternative rules given below.
+ * above rule [2] can generate infinite array of quantifiers: "word" +*{23}(,17}? would be legal.
+ * rule 5: option marker '?' makes "[]" a valid query. Propose to remove question mark.
+ * expression [11] / basic expression [12]: structural ambiguity. See proposed alternative below.
+{{{
+// rules presented in antlr format
+//--- [2v2] no left recursion or ambiguity, 1 (optional) quantifier
+main_query :
+      simple_query
+    | simple_query '|' main_query       // 'or'
+    | simple_query main_query           // sequence
+    | simple_query quantifier           // quantification
+    ;
+
+//--- [3v2]
+simple_query :
+      '(' main_query ')'
+    | implicit_query
+    | segment_query
+    ;
+
+//--- [5v2] 'expression no longer optional
+segment_query :
+      '[' expression ']'
+    ;
+
+//--- [11v2]
+expression :
+      basic_expression
+    | basic_expression '|' expression   // or
+    | basic_expression '&' expression   // and
+    ;
+
+//--- [12v2]
+basic_expression :
+      '(' expression ')'        // grouping
+    | '!' expression            // not
+    | attribute operator flagged_regexp
+    ;
+
+}}}
+