X-Git-Url: https://git.phdru.name/?a=blobdiff_plain;f=parser%2Fgrammar.ebnf;h=43752574a181addd522514c7ff8e0e16d6346e6a;hb=3db3a1c52868d865cac4e96d6521f62feb15cf77;hp=b657738ad5f30a6ab29508f8364b212faffa4708;hpb=3eadd8423e41b70e89854bd63e0e9875e259978c;p=phdru.name%2Fcgi-bin%2Fblog-ru%2Fsearch-tags.git

diff --git a/parser/grammar.ebnf b/parser/grammar.ebnf
index b657738..4375257 100644
--- a/parser/grammar.ebnf
+++ b/parser/grammar.ebnf
@@ -1,4 +1,4 @@
-# Grammar rules for tag searching; EBNF.
+# Grammar rules for tag searching
 
 # The grammar defines expressions in the following forms:
 #  TAG - search blog posts that contain the tag;
@@ -11,26 +11,41 @@
 # Allowed operators: conjunction - & && AND and
 #                    disjunction - | || OR or
 #                    negation    - ! NOT not
+# Usual priority: NOT recognized before AND, AND before OR.
 # This  is a simple version of the grammar and it allows
-# rather stupid expressions, like !!TAG or ((TAG))
+# rather stupid expressions, like (TAG) or ((TAG)) or !(!(TAG)).
 
-@@grammar :: Tags
+expression = inner_expression:e end -> e
 
-start = expression $ ;
+inner_expression = (or_expression | aterm_expression):e -> e
 
-expression = (
-           | expression and_op expression
-           | expression or_op expression
-           | not_op expression
-           | expression_parens
-           | name ) ;
+or_expression = aterm_expression:a or_op inner_expression:e -> ('OR', a, e)
 
-expression_parens = '(' expression ')' ;
+and_expression = term_expression:t and_op aterm_expression:a -> ('AND',
+t, a)
 
-name = /[a-z][a-z0-9_]+/ ;
+not_expression = not_op ws (parens_expression | name):n -> ('NOT', n)
 
-and_op = '&' | '&&' | 'AND' | 'and' ;
+aterm_expression = (and_expression | term_expression):e -> e
 
-or_op = '|' | '||' | 'OR' | 'or' ;
+term_expression = (not_expression:e -> e) | (parens_expression:p -> p) | (name:n space_b4letter -> n)
 
-not_op = '!' | 'NOT' | 'not' ;
+parens_expression = '(' ws inner_expression:e ws ')' -> ('PARENS', e)
+
+and_op = (ws ('&&' | '&') ws) | (ws ('AND' | 'and') space_b4letter)
+
+or_op = (ws ('||' | '|') ws) | (ws ('OR' | 'or') space_b4letter)
+
+not_op = (ws '!' ws) | (ws ('NOT' | 'not') space_b4letter)
+
+name = <lletter lletterOrDigit*>:n -> ('NAME', n)
+
+lletter = :l ?(l in 'abcdefghijklmnopqrstuvwxyz') -> l
+
+digit = :d ?(d in '0123456789') -> d
+
+lletterOrDigit = (lletter | digit):c -> c
+
+space_b4letter = (' '+ ~~letter) | ws
+
+# vim: set ft=text :