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diff --git a/parser/parser.py b/parser/parser.py
old mode 100644
new mode 100755
index d278e4b..3f51d3f
--- a/parser/parser.py
+++ b/parser/parser.py
@@ -1,107 +1,33 @@
-# Parse query
+#! /usr/bin/env python
 
-from ply import lex, yacc
+import os
+from parsley import makeGrammar
 
-literals = '()'
 
-tokens = ('NAME', 'AND_OP', 'OR_OP', 'NOT_OP', 'SP1')
+# cache
+_grammar = None
 
-t_NAME = '[a-z][a-z0-9_]*'
 
-t_AND_OP = '&'
+def load_grammar():
+    global _grammar
+    parser_dir = os.path.dirname(__file__)
+    with open(os.path.join(parser_dir, 'grammar.ebnf'), 'rt') as grammar_file:
+        grammar_text = grammar_file.read()
+    _grammar = makeGrammar(grammar_text, {}, 'Tags')
 
-t_OR_OP = r'\|'
 
-t_NOT_OP = '!'
+def parse(input):
+    if _grammar is None:
+        load_grammar()
+    return _grammar(input).expression()
 
-t_SP1 = '[ \t]+'
 
-def t_error(t):
-    """Avoid warnings on stderr"""
-
-lexer = lex.lex()
-
-def p_expression_name(p):
-    """expression : NAME"""
-    p[0] = ('NAME', p[1])
-
-def p_expression_and_and(p):
-    """expression : expression SP0 AND_OP AND_OP SP0 expression"""
-    p[0] = ('AND', p[1], p[6])
-
-def p_expression_and(p):
-    """expression : expression SP0 AND_OP SP0 expression"""
-    p[0] = ('AND', p[1], p[5])
-
-def p_expression_and_word(p):
-    """expression : l_expression and_word r_expression"""
-    p[0] = ('AND', p[1], p[3])
-
-def p_expression_not(p):
-    """expression : NOT_OP SP0 expression"""
-    p[0] = ('NOT', p[3])
-
-def p_expression_or_or(p):
-    """expression : expression SP0 OR_OP OR_OP SP0 expression"""
-    p[0] = ('OR', p[1], p[6])
-
-def p_expression_or(p):
-    """expression : expression SP0 OR_OP SP0 expression"""
-    p[0] = ('OR', p[1], p[5])
-
-def p_expression_in_parens(p):
-    """expression : expression_parens"""
-    p[0] = p[1]
-
-def p_l_expression(p):
-    """l_expression : expression_parens
-                    | expression SP1
-    """
-    if len(p) == 2:
-        p[0] = p[1]
-    elif len(p) == 3:
-        p[0] = p[1]
-    else:
-        raise ValueError(p)
-
-def p_r_expression(p):
-    """r_expression : expression_parens
-                    | SP1 expression
-    """
-    if len(p) == 2:
-        p[0] = p[1]
-    elif len(p) == 3:
-        p[0] = p[2]
-    else:
-        raise ValueError(p)
-
-def p_expression_parens(p):
-    """expression_parens : '(' SP0 expression SP0 ')'"""
-    p[0] = ('PARENS', p[3])
-
-def p_and_word(p):
-    """and_word : NAME"""
-    if p[1] in ('AND', 'and'):
-        p[0] = p[1]
-    else:
-        raise SyntaxError
-
-def p_SP0(p):
-    """SP0 : SP1
-           | empty
-    """
-
-def p_empty(p):
-    """empty :"""
-
-def p_error(p):
-    """Avoid warnings on stderr"""
-    yacc.restart()
-
-precedence = (
-    ('left', 'OR_OP'),
-    ('left', 'AND_OP'),
-    ('right', 'NOT_OP'),
-)
-
-parser = yacc.yacc()
+if __name__ == '__main__':
+    print parse('test')
+    print parse('!test')
+    print parse('not test')
+    print parse('foo or bar')
+    print parse('foo && bar')
+    print parse('(test)')
+    print parse('(foo || bar)')
+    print parse('(foo and !bar)')