stub for optimizer

git-svn-id: http://galileo.dmi.unict.it/svn/relational/trunk@73 014f5005-505e-4b48-8d0a-63407b615a7c

CHANGELOG

@@ -50,4 +50,4 @@
 - Added __eq__ to relation object, will compare ignoring order.
 - New default relation's format is csv, as defined in RFC4180
 - Converted sample's relations to csv
-- Deb postinstall generates optimized files
+- Deb postinstall generates optimized files, this will increase loading speed

optimizer.py

@@ -0,0 +1,55 @@
+# coding=UTF-8
+# Relational
+# Copyright (C) 2008  Salvo "LtWorf" Tomaselli
+# 
+# Relation is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# 
+# author Salvo "LtWorf" Tomaselli <tiposchi@tiscali.it>
+
+'''This module optimizes relational expressions into ones that require less time to be executed'''
+
+RELATION=0
+UNARY=1
+BINARY=2
+
+class node (object):
+    '''This class is a node of a relational expression. Leaves are relations and internal nodes are operations.'''
+    def __init__(self,expression):
+        '''expression must be a valid relational algrbra expression that would be accepted by the parser
+        and must be utf16'''
+        self.kind=0
+        self.name="a"
+        self.prop=""
+        '''*-ᑌᑎᐅᐊᐅLEFTᐊᐅRIGHTᐊᐅFULLᐊπσρ'''
+        
+        '''(a ᑌ (a ᑌ b ᑌ c ᑌ d)) ᑎ c - σ i==3(πa,b(aᑌ b ᑎ c))'''
+        
+        for i in list(expression):
+            print i
+        
+        
+    def __str__(self):
+        if (self.kind==RELATION):
+            return self.name
+        elif (self.kind==UNARY):
+            return self.name + " "+ self.prop+ " (" + self.child +")"
+        elif (self.kind==BINARY):
+            return "("+ self.left + ") " + self.name + " (" + self.right+ ")"
+
+
+
+
+
+n=node(u"(a ᑌ b) ᑌ c ᑌ d")
+print n