Changed calc example grammar. Removed logging module from calc example.

examples/calc.py

@@ -13,29 +13,36 @@
 from arpeggio import *
 from arpeggio.export import PMDOTExport, PTDOTExport
 from arpeggio import RegExMatch as _
-import logging        
 
 def number():     return _(r'\d*\.\d*|\d+')
-def factor():           return [number, ("(", expression, ")")]
+def factor():     return Optional(["+","-"]), [number,
+                          ("(", expression, ")")]
 def term():       return factor, ZeroOrMore(["*","/"], factor)
-def expression():       return Optional(["+","-"]), term, ZeroOrMore(["+", "-"], term)
-def calc():             return expression, EndOfFile
+def expression(): return term, ZeroOrMore(["+", "-"], term)
+def calc():       return OneOrMore(expression), EndOfFile
+
 
 # Semantic actions
 class ToFloat(SemanticAction):
     '''Converts node value to float.'''
     def first_pass(self, parser, node, nodes):
-        logging.debug("Converting %s." % node.value)
+        print "Converting %s." % node.value
         return float(node.value)
 
 class Factor(SemanticAction):
     '''Removes parenthesis if exists and returns what was contained inside.'''
     def first_pass(self, parser, node, nodes):
-        logging.debug("Factor %s" % nodes)
-        if nodes[0] == "(":
-            return nodes[1]
-        else:
+        print "Factor %s" % nodes
+        if len(nodes) == 1:
             return nodes[0]
+        sign = -1 if nodes[0] == '-' else 1
+        next = 0
+        if nodes[0] in ['+', '-']:
+            next = 1
+        if nodes[next] == '(':
+            return sign * nodes[next+1]
+        else:
+            return sign * nodes[next]
 
 class Term(SemanticAction):
     '''
@@ -43,14 +50,14 @@ class Term(SemanticAction):
     Factor nodes will be already evaluated.
     '''
     def first_pass(self, parser, node, nodes):
-        logging.debug("Term %s" % nodes)
+        print "Term %s" % nodes
         term = nodes[0]
         for i in range(2, len(nodes), 2):
             if nodes[i-1]=="*":
                 term *= nodes[i]
             else:
                 term /= nodes[i]
-        logging.debug("Term = %f" % term)
+        print "Term = %f" % term
         return term
 
 class Expr(SemanticAction):
@@ -59,7 +66,7 @@ class Expr(SemanticAction):
     Term nodes will be already evaluated.
     '''
     def first_pass(self, parser, node, nodes):
-        logging.debug("Expression %s" % nodes)
+        print "Expression %s" % nodes
         expr = 0
         start = 0
         # Check for unary + or - operator
@@ -72,7 +79,7 @@ class Expr(SemanticAction):
             else:
                 expr += nodes[i]
 
-        logging.debug("Expression = %f" % expr)
+        print "Expression = %f" % expr
         return expr
 
 class Calc(SemanticAction):
@@ -88,8 +95,6 @@ calc.sem = Calc()
 
 if __name__ == "__main__":
     try:
-        logging.basicConfig(level=logging.DEBUG)
-
         # First we will make a parser - an instance of the calc parser model.
         # Parser model is given in the form of python constructs therefore we
         # are using ParserPython class.

examples/calc_peg.py

@@ -24,9 +24,10 @@ from calc import ToFloat, Factor, Term, Expr, Calc
 # Grammar is defined using textual specification based on PEG language.
 calc_grammar = """
         number <- r'\d*\.\d*|\d+';
-        factor <- number / "(" expression ")";
+        factor <- ("+" / "-")?
+                  (number / "(" expression ")");
         term <- factor (( "*" / "/") factor)*;
-        expression <- ("+" / "-")? term (("+" / "-") term)*;
+        expression <- term (("+" / "-") term)*;
         calc <- expression EndOfFile;
 """